Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
General Description
The MAX8934G dual-input Li+/Li-Poly linear battery char-
ger with Smart Power SelectorK safely charges a single
Li+/Li-Poly cell in accordance with JEITA* recommenda-
tions. The MAX8934G monitors the battery temperature
(TBATT) while charging, and automatically adjusts the
fast-charge current and charge termination voltage as the
battery temperature varies. The MAX8934G also monitors
the battery temperature while the battery is discharging,
and provides a warning flag (OT) to the system in the
event that the battery is over temperature. Safety region
2 is supported (see Figure 6 for details). An ultra-low IQ,
always-on LDO provides an additional 3.3V supply for
system power.
The MAX8934G operates with either separate inputs
for USB and AC adapter power, or from a single input
that accepts both. All power switches for charging and
switching the load between battery and external power
are included on-chip. No external MOSFETs are required.
The MAX8934G features a Smart Power Selector to make
the best use of limited USB or adapter power. Input cur-
rent limit and battery charge current limit are indepen-
dently set. Input power not used by the system charges
the battery. Charge current limit and DC current limit can
be set up to 1.5A and 2A, respectively, while USB input
current can be set to 100mA or 500mA. Automatic input
selection switches the system load from battery to external
power.
The MAX8934G provides a SYS output voltage of 4.35V.
Other features include overvoltage protection (OVP),
open-drain charge status and fault outputs, power-OK
monitors, charge timers, and a battery thermistor moni-
tor. Additionally, on-chip thermal limiting reduces the
battery charge-rate to prevent charger overheating.
The MAX8934G is available in a 28-pin, 4mm x 4mm,
TQFN package.
Applications
PDAs, Palmtop, and Wireless Handhelds
Portable Media, MP3 Players, and PNDs
Digital Still Cameras and Digital Video Cameras
Handheld Game Systems
Features
S Li+ Charger with Smart Power Selector, No
External MOSFETs Needed
S Monitors Battery Temperature and Adjusts Charge
Current and Termination Voltage Automatically
per JEITA Recommendations
S OT Flags System of a Hot Battery During
Discharge
S Ultra-Low IQ, Always-On 3.3V LDO
S Common or Separate USB and Adapter Inputs
S Automatic Adapter/USB/Battery Switchover
S Load Peaks in Excess of Adapter Rating are
Supported by Battery
S Input OVP to 16V (DC) and 9V (USB)
S 40mI SYS-to-BATT Switch
S Thermal Regulation Prevents Overheating
S 4.35V SYS Regulation Voltage
Typical Operating Circuit
+Denotes a lead(Pb)-free/RoHS-compliant package.
**EP = Exposed pad.
Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.
Ordering Information
*JEITA (Japan Electronics and Information Technology
Industries Association) Standard, A Guide to the Safe Use of
Secondary Lithium Ion Batteries on Notebook–Type Personal
Computers, April 20, 2007.
19-5296; Rev 0; 6/10
PART TEMP RANGE PIN-PACKAGE
MAX8934GETI+ -40NC to +85NC28 Thin QFN-EP**
MAX8934G
SYS
LDO
GND
CHARGE
CURRENT
LOAD
CURRENT
BATT BATTERY
SYSTEM
LOAD
AC
ADAPTER
CHARGE
AND
SYS LOAD
SWITCH
USB
DC Q1
Q2
Q3
USB
3.3V ALWAYS-ON
LINEAR
REGULATOR
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
2
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
DC, PEN1 to GND .................................................-0.3V to +16V
USB to GND ............................................................-0.3V to +9V
VL to GND ...............................................................-0.3V to +4V
LDO to GND ......... -0.3V to the lower of +4V and (VSYS + 0.3V)
THMEN, THMSW to GND ..................... -0.3V to +(VLDO + 0.3V)
THM to GND .......................................-0.3V to (VTHMSW + 0.3V)
PSET, ISET, CT to GND ............................... -0.3V to (VL + 0.3V)
BATT, SYS, CEN, CHG, OT, DOK,
UOK, FLT, DONE, USUS, PEN2 to GND .............-0.3V to +6V
EP (Exposed Pad) to GND ................................... -0.3V to +0.3V
DC Continuous Current (total in two pins) ....................2.4ARMS
SYS Continuous Current (total in two pins) ...................2.4ARMS
USB Continuous Current (total in two pins) ..................2.0ARMS
BATT Continuous Current (total in two pins) .................2.4ARMS
LDO Continuous Current .............................................50mARMS
LDO Short-Circuit Duration .........................................Continuous
Continuous Power Dissipation (TA = +70NC)
Single-Layer Board
(derate 20.8mW/NC above +70NC) ...................... 1666.7mW
Multilayer Board
(derate 28.6mW/NC above +70NC) ...................... 2285.7mW
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature ...................................... -40NC to +125NC
Storage Temperature ....................................... -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
ELECTRICAL CHARACTERISTICS
(VDC = VPEN1 = VPEN2 = 5V, CEN = USUS = THMEN = GND, VBATT = 4V, VTHM = 1.65V, USB, THMSW, CHG, DONE, OT, DOK,
UOK, FLT are unconnected, CCT = 0.068FF, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 1)
ABSOLUTE MAXIMUM RATINGS
PARAMETER CONDITIONS MIN TYP MAX UNITS
DC-to-SYS PREREGULATOR
DC Operating Voltage Range 4.1 6.6 V
DC Withstand Voltage VBATT = VSYS = 0V 14 V
DC Undervoltage Threshold When V
DOK goes low, VDC rising, 500mV hysteresis 3.95 4.0 4.05 V
DC Overvoltage Threshold When V
DOK goes high, VDC rising, 360mV hysteresis 6.8 6.9 7.0 V
DC Operating Supply Current ISYS = IBATT = 0mA, V
CEN = 0V 1 2 mA
ISYS = IBATT = 0mA, V
CEN = 5V 0.8 1.5
DC Suspend Current VDC = V
CEN = VUSUS = 5V, VPEN1 = 0V 195 340 FA
DC-to-SYS On-Resistance ISYS = 400mA, V
CEN = 5V 0.2 0.35 I
DC to BATT Dropout Voltage When SYS regulation and charging stops, VDC falling,
150mV hysteresis 10 50 90 mV
DC Current Limit VDC = 5V, VSYS = 4V,
TA = +25NC
RPSET = 1.5kI1800 2000 2200
mA
RPSET = 3kI900 1000 1100
RPSET = 6.3kI450 475 500
VPEN1 = 0V, VPEN2 = 5V
(500mA USB mode) 450 475 500
VPEN1 = VPEN2 = 0V
(100mA USB mode) 80 95 100
PSET Resistance Range 1.5 6.3 kI
SYS Regulation Voltage VDC = 6V, ISYS = 1mA to 1.75A, V
CEN = 5V 4.29 4.35 4.4 V
Input Current Soft-Start Time Connecting DC with USB not present 1.5 ms
Connecting DC with USB present 50 Fs
Thermal-Limit Temperature Die temperature at when the charging current and input
current limits are reduced 100 NC
Thermal-Limit Gain ISYS reduction with die temperature (above +100NC) 5 %/C
VL Voltage IVL = 0 to 5mA, USB = unconnected 3 3.3 3.6 V
3
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VPEN1 = VPEN2 = 5V, CEN = USUS = THMEN = GND, VBATT = 4V, VTHM = 1.65V, USB, THMSW, CHG, DONE, OT, DOK,
UOK, FLT are unconnected, CCT = 0.068FF, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
USB-TO-SYS PREREGULATOR
USB Operating Voltage Range 4.1 6.6 V
USB Withstand Voltage VBATT = VSYS = 0V 8 V
USB Undervoltage Threshold When V
UOK goes low, VUSB rising, 500mV hysteresis 3.95 4.0 4.05 V
USB Overvoltage Threshold When V
UOK goes high, VUSB rising, 360mV hysteresis 6.8 6.9 7.0 V
USB Operating Supply Current ISYS = IBATT = 0mA, V
CEN = VPEN2 = 0V 1 2 mA
ISYS = IBATT = 0mA, V
CEN = 5V, VPEN2 = 0V 0.9 1.5
USB Suspend Current DC = unconnected, VUSB = V
CEN = VUSUS = 5V 190 340 FA
USB to SYS On-Resistance DC unconnected, VUSB = V
CEN = 5V, ISYS = 400mA 0.22 0.33 I
USB-to-BATT Dropout Voltage When SYS regulation and charging stops, VUSB falling,
150mV hysteresis 10 50 90 mV
USB Current Limit
(See Table 2)
DC unconnected,
VUSB = 5V, TA = +25NC
VPEN1 = 0V, VPEN2 = 5V 450 475 500 mA
VPEN1 = VPEN2 = 0V 80 95 100
SYS Regulation Voltage DC unconnected, VUSB = 6V, VPEN2 = 5V, ISYS = 1mA
to 400mA, VCEN = 5V 4.29 4.35 4.4 V
Input Limiter Soft-Start Time Input current ramp time 50 Fs
Thermal-Limit Temperature Die temperature at when the charging current and input
current limits are reduced 100 NC
Thermal-Limit Gain ISYS reduction with die temperature (above +100NC) 5%/NC
VL Voltage DC unconnected, VUSB = 5V, IVL = 0 to 5mA 3 3.3 3.6 V
LDO LINEAR REGULATOR
LDO Output Voltage
DC unconnected, VUSB = 5V, ILDO = 0mA 3.234 3.3 3.366
VVDC = 5V, USB unconnected, ILDO = 0mA 3.234 3.3 3.366
DC and USB unconnected, VBATT = 4V, ILDO = 0mA 3.234 3.3 3.366
LDO Load Regulation ILDO = 0 to 30mA 0.003 %/mA
BATTERY CHARGER
BATT-to-SYS On-Resistance VDC = 0V, VBATT = 4.2V, ISYS = 1A 0.04 0.08 I
BATT-to-SYS Reverse
Regulation Voltage VPEN1 = VPEN2 = 0V, ISYS = 200mA 50 75 105 mV
BATT Regulation Voltage—Safety
Region 2 IBATT = 0mA
TA = +25NC, VTHM_T2 < VTHM <
VTHM_T3 4.175 4.2 4.225
V
TA = 0NC to +85NC, VTHM_T2 <
VTHM < VTHM_T3 4.158 4.2 4.242
TA = +25NC, VTHM_T1 < VTHM <
VTHM_T2 or VTHM_T3 < VTHM <
VTHM_T4
4.05 4.075 4.1
TA = 0NC to +85NC, VTHM_T1 <
VTHM < VTHM_T2 or VTHM_T3 <
VTHM < VTHM_T4
4.034 4.075 4.1
4
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VPEN1 = VPEN2 = 5V, CEN = USUS = THMEN = GND, VBATT = 4V, VTHM = 1.65V, USB, THMSW, CHG, DONE, OT, DOK,
UOK, FLT are unconnected, CCT = 0.068FF, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
BATT Recharge Threshold—
Safety Region 2
Change in VBATT
from DONE to fast-
charge restart
VTHM_T2 < VTHM < VTHM_T3 -145 -104 -65
mV
VTHM_T1 < VTHM < VTHM_T2 or
VTHM_T3 < VTHM < VTHM_T4 -120 -80 -40
BATT Fast-Charge
Current Range RISET = 10kI to 2kI 0.3 1.5 A
BATT Charge Current Accuracy
VSYS = 5.5V,
VTHM_T1 < VTHM
< VTHM_T4 (safety
region 2)
RISET = 2kI1350 1500 1650
mA
RISET = 4kI675 750 825
RISET = 10kI270 300 330
RISET = 2kI, VBATT = 2.5V
(prequal) 270 300 330
RISET = 4kI, VBATT = 2.5V
(prequal) 130 150 170
RISET = 10kI, VBATT = 2.5V
(prequal) 60
ISET Output Voltage RISET = 4kI, IBATT = 500mA (VISET = 1.5V at full
charge current) VTHM_T1 < VTHM < VTHM_T4 0.9 1 1.1 V
Charger Soft-Start Time Charge-current ramp time 1.5 ms
BATT Prequal Threshold VBATT rising, 180mV hysteresis 2.9 3 3.1 V
BATT Input Current VBATT = 4.2V,
ILDO = 0
No DC or USB power
connected, THMEN = low,
VCEN = 5V
5 12
FA
No DC or USB power
connected, THMEN = high,
V
CEN = 5V
12 25
DC or USB power connected,
V
CEN = 5V 0.003 2
DONE Threshold as a
Percentage of Fast-Charge
Current
IBATT decreasing 20 %
Maximum Prequal Time From CEN falling to end of prequal charge, VBATT = 2.5V 180 min
Maximum Fast-Charge Time From CEN falling to FLT falling 300 min
Maximum Top-Off Time 15 s
Timer Accuracy -20 +20 %
Timer Extend Threshold Percentage of fast-charge current below where the timer
clock operates at half-speed 50 %
Timer Suspend Threshold Percentage of fast-charge current below where timer
clock pauses 20 %
5
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VPEN1 = VPEN2 = 5V, CEN = USUS = THMEN = GND, VBATT = 4V, VTHM = 1.65V, USB, THMSW, CHG, DONE, OT, DOK,
UOK, FLT are unconnected, CCT = 0.068FF, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 1)
Note 1: Limits are 100% production tested at TA = +25NC. Limits over the operating temperature range are guaranteed by design.
Note 2: NC includes external NTC thermistor error. % of THMSW excludes thermistor beta error and external pullup error. NTC
thermistor assumed to be 100kI Q1% nominal, part number Vishay NTHS0603N01N1003FF, external pullup resistor =
100kI Q1%.
PARAMETER CONDITIONS MIN TYP MAX UNITS
THERMISTOR MONITOR (Beta = 3964) (Note 2)
THM Cold No-Charge Threshold
(T1) ICHG = 0A, when charging is suspended, 2NC hysteresis
-2.1 0 +2.4 NC
76.4 77.2 77.9 % of
THMSW
THM Cold Threshold (T2) VBATT_REG, reduced, 2NC hysteresis
8.2 10 12 NC
66.2 67 67.6 % of
THMSW
THM Hot Threshold (T3) VBATT_REG reduced, 2.5NC hysteresis
42.8 45 47.5 NC
29.8 30 30.6 % of
THMSW
THM Hot No-Charge Threshold
(T4)
ICHG = 0mA, when charging is suspended, 3NC
hysteresis
57 60 63.5 NC
19.5 19.8 20.1 % of
THMSW
THM Hot Discharge Threshold
(TOT)OT asserts low, 5NC hysteresis
71 75 80 NC
12.6 12.9 13.1 % of
THMSW
THM Input leakage THM = GND or LDO TA = +25NC-1 +0.001 +1 FA
TA = +85NC0.01
THMSW Output Leakage THMSW = GND TA = +25NC-0.2 +0.001 +1 FA
TA = +85NC0.01
THMSW Output Voltage High Sourcing 1mA VLDO -
0.05 V
LOGIC I/O: PEN1, PEN2, CHG, FLT, DONE, DOK, UOK, USUS, THMEN)
Logic-Input Thresholds
High level 1.3 V
Low level 0.4
Hysteresis 50 mV
Logic-Input Leakage Current VIN = 0 to 5.5V TA = +25NC0.001 1 FA
TA = +85NC0.01
Logic-Low Output Voltage Sinking 1mA 25 100 mV
Logic-High Output Leakage
Current VOUT = 5.5V TA = +25NC0.001 1 FA
TA = +85NC0.01
6
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
USB OPERATING SUPPLY CURRENT
vs. USB VOLTAGE (CHARGER ENABLED)
MAX8934G toc01
USB OPERATIN SUPPLY CURRENT (µA)
200
400
600
800
1000
1200
0
USB VOLTAGE (V)
7645231
08
VBATT = 4.2V,
VUSUS = 0V
CHARGER IN
DONE MODE
ISYS = 0A
VUSB RISING
VUSB FALLING
ENTERING OVLO
USB OPERATING SUPPLY CURRENT
vs. USB VOLTAGE (CHARGER DISABLED)
MAX8934G toc02
USB VOLTAGE (V)
USB OPERATING SUPPLY CURRENT (µA)
764 52 31
100
200
300
400
500
600
700
800
900
0
08
VBATT = 4.2V,
VUSUS = 0V
CEN = 1
ISYS = 0A
PEN1 = X, PEN2 = 1
VUSB RISING
VUSB FALLING
ENTERING OVLO
USB SUSPEND CURRENT
vs. USB VOLTAGE
MAX8934G toc03
USB VOLTAGE (V)
USB QUIESCENT CURRENT (FA)
7654321
50
100
150
200
250
0
08
VBATT = 4.2V,
USUS = 1
BATTERY INPUT CURRENT
vs. BATTERY VOLTAGE
(USB DISCONNECTED)
MAX8934G toc04
BATTERY VOLTAGE (V)
BATTERY INPUT CURRENT (uA)
4321
2
4
6
8
10
12
14
0
05
THMEN = 1
THMEN = 0
CHARGE CURRENT (mA)
50
100
150
200
250
300
350
400
450
500
0
CHARGE CURRENT
vs. BATTERY VOLTAGE (500mA USB)
MAX8934G toc07
BATTERY VOLTAGE (V)
1234
05
VUSB = 5V
PEN1 = X, PEN2 = 1
VBATT RISING
VBATT FALLING
CHARGE CURRENT
vs. BATTERY VOLTAGE (1A DC)
MAX8934G toc08
BATTERY VOLTAGE (V)
CHARGE CURRENT (mA)
4321
200
400
600
800
1000
1200
0
05
VDC = 5V
PEN1 = 1, PEN2 = X
VBATT RISING
VBATT FALLING
BATTERY INPUT CURRENT
vs. TEMPERATURE
MAX8934G toc05
TEMPERATURE (°C)
BATTERY INPUT CURRENT (µA)
603510-15
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
5.0
4.0
-40 85
VBATT = 4V, THMEN = 0, ILDO = 0
USB AND DC UNCONNECTED
CHARGE CURRENT vs.
BATTERY VOLTAGE (100mA USB)
MAX8934G toc06
BATTERY VOLTAGE (V)
CHARGE CURRENT (mA)
4321
10
20
30
40
50
60
70
80
90
100
0
05
VUSB = 5V
PEN1 = X, PEN2 = 0
VBATT RISING
VBATT FALLING
7
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics (continued)
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
SYS OUTPUT VOLTAGE
vs. SYS OUTPUT CURRENT (DC)
MAX8934G toc14
SYS CURRENT (A)
SYS VOLTAGE (V)
2.52.01.51.00.5
3.9
4.3
4.7
5.1
5.5
3.5
0.0 3.0
VDC = 6V
VDC = 5V
VBAT = 4V
PEN1 = 1, PEN2 = X
CEN = 1
BATTERY REGULATION VOLTAGE
vs. TEMPERATURE
MAX8934G toc10
BATTERY VOLTAGE (V)
BATTERY REGULATION VOLTAGE (V)
603510-15
4.175
4.180
4.185
4.190
4.195
4.200
4.205
4.210
4.215
4.220
4.170
-40 85
SYS OUTPUT VOLTAGE
vs. DC VOLTAGE
MAX8934G toc12
DC VOLTAGE (V)
12
108642
01
4
SYS VOLTAGE (V)
4.2
4.4
4.6
4.8
4.0
VBATT = 4.0V
NO SYS LOAD
NORMALIZED CHARGE CURRENT
vs. AMBIENT TEMPERATURE
(LOW IC POWER DISSIPATION)
MAX8943G toc09
AMBIENT TEMPERATURE (°C)
NORMALIZED CHARGE CURRENT
6035-15 10
0.9925
0.9950
0.9975
1.0000
1.0050
1.0025
1.0075
1.0100
0.9900
-40 85
VUSB = 5V, VBATT = 4V
SYS OUTPUT VOLTAGE
vs. USB VOLTAGE
MAX8934G toc11
USB VOLTAGE (V)
SYS VOLTAGE (V)
7654321
4.2
4.4
4.6
4.8
4.0
08
VBATT = 4.0V
NO SYS LOAD
SYS OUTPUT VOLTAGE vs. SYS OUTPUT
CURRENT (USB AND DC DISCONNECTED)
MAX8934G toc13
SYS OUTPUT CURRENT (A)
SYS OUTPUT VOLTAGE (V)
1.51.00.5
3.7
3.8
3.9
4.0
4.1
4.2
4.3
4.4
4.5
3.6
0 2.0
VBATT = 4.0V
THE SLOPE OF THIS LINE
SHOWS THAT THE BATT-TO-SYS
RESISTANCE IS 40mI.
8
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics (continued)
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
VL OUTPUT VOLTAGE vs.
DC VOLTAGE
MAX8934G toc16
DC VOLTAGE (V)
VL OUTPUT VOLTAGE (V)
12108642
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
01
4
IVL = 5mA
IVL = 0mA
CHARGE PROFILE—820mAh BATTERY
ADAPTER INPUT—1A CHARGE
TIME (min)
BATTERY CURRENT (mA)
604020
0.2
0.4
0.6
0.8
1.0
1.2
0
08
0
MAX8934G toc18
BATTERY VOLTAGE (V)
2.5
3.0
3.5
4.0
4.5
1.5
2.0
VBAT
IBAT
DC CONNECT WITH NO USB
(RSYS = 22I)
MAX8934G toc20
3.6V
4.35V
3.6V
0A
1.2A
-1A
1A/div
5V/div
5V/div
1A/div
VBATT
VSYS
IDC
IBATT
400µs/div
160mA 0mA
BATTERY CHARGER SOFT-START
CSYS CHARGING
CDC
CHARGING
SYS OUTPUT VOLTAGE vs.
SYS OUTPUT CURRENT (USB)
MAX8934G toc15
SYS OUTPUT CURRENT (A)
SYS OUTPUT VOLTAGE (V)
2.52.01.51.00.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
5.5
3.5
0 3.0
VBATT = 4.0V,
VUSB = 5.0V
CEN = 1
0.1A, PEN1 = 0, PEN2 = 0
0.5A, PEN1 = 0, PEN2 = 0
CHARGE PROFILE—820mAh BATTERY
USB INPUT—500mA CHARGE
MAX8934G toc17
TIME (min)
BATTERY CURRENT (mA)
BATTERY VOLTAGE (V)
100806040200 120
50
100
150
200
250
300
350
400
450
500
0
2.5
3.0
3.5
4.0
4.5
2.0
IBAT
VBAT
DC CONNECT WITH USB CONNECTED
(RSYS = 22I)
MAX8934G toc19
4.35V
3.8V
0A
475mA
1.2A
-1A
0A
1A/div
5V/div
1A/div
500mA/div
VSYS
IDC
IUSB
IBATT
400µs/div
-303mA
BATTERY CHARGER SOFT-START
CDC CHARGING CSYS CHARGING
9
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics (continued)
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
USB CONNECT WITH NO DC
(RSYS = 22I)
MAX8934G toc22
5V
3.3V
3.3V
3.3V
-150mA
475mA
3.7V4.3V
-1A
5V/div
5V/div
5V/div
5V/div
500mA/div
500mA/div
VUSB
IUSB
VSYS
VUOK
IBATT
200µs/div
BATTERY CHARGER
SOFT-START
CSYS CHARGING
CDC CHARGING
-307mA
VCHG
USB SUSPEND (RSYS = 22I)
MAX8934G toc24
3.3V 5V/div
VUSUS
VSYS
IUSB
200µs/div
3.7V
-307mA
3.6V
3.3V
VCHG
IBATT
475mA 0A
0V
160mA
VUSB = 5V
5V/div
5V/div
500mA/div
500mA/div
LDO OUTPUT VOLTAGE vs. LDO OUTPUT
CURRENT (USB DISCONNECTED)
MAX8934G toc26
LDO OUTPUT CURRENT (mA)
LDO OUTPUT VOLTAGE (V)
15012525 50 75 100
3.00
3.05
3.10
3.15
3.20
3.25
3.30
3.35
2.95
0 175
VDC = 5.0V
VBATT = 4.0V
DC UNCONNECTED
DC DISCONNECT WITH NO USB
(RSYS = 22I)
MAX8934G toc21
3.6V
3.6V
4V
0A
-1A
1A/div
5V/div
5V/div
1A/div
VBATT
VSYS
IDC
IBATT
200µs/div
160mA
-IBATT = CHARGING
1.2A
USB DISCONNECT WITH NO DC
(RSYS = 22I)
MAX8934G toc23
4.2V 0V 5V/div
VUSB
VSYS
IUSB
200µs/div
0mA
3.7V 3.6V
3.3V
3.3V
VUOK
IBATT
VCHG
-307mA
475mA
160mA
5V/div
5V/div
5V/div
500mA/div
500mA/div
USB RESUME (RSYS = 22I)
MAX8934G toc25
5V/div
VUSUS
VSYS
IUSB
200µs/div
3.7V
3.6V 4.3V
3.3V
VCHG
IBATT
3V
0A
160mA
475mA
VUSB = 5V
5V/div
5V/div
500mA/div
500mA/div
0V
-307mA
BATTERY CHARGER
SOFT-START
10
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics (continued)
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
LDO STARTUP WAVEFORMS
MAX8934G toc27
2V/div
50mA/div
2V/div
IBATT
VLDO
VBATT
400Fs/div
3.6V
ILDO = 0
3.3V
ALWAYS-ON LDO POWER-SUPPLY
REJECTION RATIO vs. FREQUENCY
MAX8934G toc29
FREQUENCY (kHz)
PSRR (dB)
101
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
-50
0.1 100
VSYS = 3.6V
ILDO = 10mA
RESISTIVE LOAD
THM NORMAL TO
THM COLD (< T2) TRANSITION
MAX8934G toc31
1V/div
200mV/div
200mA/div
VTHM
VBAT
IBAT
10ms/div
10I RESISTOR FROM BATT TO GND
4.2V
4.075V
2.2V
420mA
LDO OUTPUT VOLTAGE vs.
BATTERY VOLTAGE
MAX8934G toc28
BATTERY VOLTAGE (V)
LDO OUTPUT VOLTAGE (V)
3.53.02.52.01.51.00.5
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
0 4.0
VBATT RISING
VBATT FALLING
LDO NOISE DENSITY
vs. FREQUENCY
MAX8934G toc30
FREQUENCY (kHz)
OUTPUT NOISE (nV/Hz)
10001001010.1
100
200
300
400
500
600
700
800
900
0
0.01 10,000
VBATT = 3.8V,
ILDO = 10mA
RESISTIVE LOAD
11
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Typical Operating Characteristics (continued)
(TA = +25NC, circuit of Figure 2, VDC = 6V, VBATT = 3.6V, thermistor Beta = 3964, unless otherwise noted. Negative battery current
indicates charging.)
THM NORMAL TO THM HOT NO
CHARGE (> T4) TRANSITION
MAX8934G toc33
500mV/div
2V/div
100mA/div
IBATT
VBATT
VTHM
20ms/div
0.65V
4.2V
0V
0mA
100mA
4.075V
HP6060B ELECTRONIC
LOAD SET TO CC MODE
THM NORMAL TO T2 TO T1
(COLD, NO CHARGE) TRANSITION
MAX8934G toc35
1V/div
1V/div
200mA/div
VTHM
VBATT
IBATT
10ms/div
10I RESISTOR FROM BATT TO GND
4.2V
0V
0mA
4.075V
2.54V
2.2V
420mA
MAX8934G toc34
2V/div
2V/div
2V/div
2V/div
VTHM
VBATT
VSYS
4ms/div
THM NORMAL TO THM HOT
THRESHOLD DISCHARGE TOT
VOT 3V
3.6V
3.6V
0.425V
THM NORMAL TO THM HOT
(> T3) TRANSITION
MAX8934G toc32
500mV/div
200mV/div
500mA/div
IBATT
VBATT
VTHM
10ms/div
1.0V
4.2V
HP6060B ELECTRONIC LOAD
SET TO CC MODE
4.075V
940mA
12
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Pin Description
PIN NAME FUNCTION
1DONE Charge Complete Output. The DONE active-low, open-drain output pulls low when the charger enters
the DONE state. The charger current = 0mA when DONE is low. See Figure 7.
2, 3 DC
DC Power Input. DC is capable of delivering up to 2A to SYS. DC supports both AC adapter and USB
inputs. The DC current limit is set with PEN1, PEN2, and RPSET. See Table 2. Both DC pins must be
connected together externally. Connect a 10FF ceramic capacitor from DC to GND. The DC inputs should
be grounded if not used.
4CEN
Active-Low Charger Enable Input. Connect CEN to GND or drive low with a logic signal to enable
battery charging when a valid source is connected at DC or USB. Drive high with a logic signal to
disable battery charging.
5 PEN1 Input Limit Control 1. See Table 2 for complete information.
6 PEN2 Input Limit Control 2. See Table 2 for complete information.
7 PSET DC Input Current-Limit Setting. Connect a resistor from PSET to GND to program the DC current limit up
to 2A (3000V/RPSET).
8 VL
Internal Logic LDO Output Bypass Pin. Provides 3.3V when DC or USB is present. Connect a 0.1FF
ceramic capacitor from VL to GND. VL powers the internal circuitry and provides up to 5mA to an
external load.
9, 13 GND Ground. Both GND pins must be connected together externally.
10 CT Charge Timer Program Input. A capacitor from CT to GND sets the maximum prequal and fast-charge
timers. Connect CT to GND to disable the timer.
11 ISET
Charge Current-Limit Setting. A resistor (RISET) from ISET to GND programs the fast-charge charge
current up to 1.5A (3000V/RISET). The prequal charge current is 20% of the set fast-charge charge
current.
12 USUS USB Suspend Digital Input. As shown in Table 2, driving USUS high suspends the DC or USB inputs if
they are configured as a USB power input.
14 THM
Thermistor Input. Connect a negative temperature coefficient (NTC) thermistor with good thermal
contact with the battery from THM to GND. Use a thermistor with Beta = 3964. Connect a resistor
of equal resistance to the thermistor resistance at +25°C from THM to THMSW so that the battery
temperature can be monitored, and the fast-charge current and/or the charge termination voltage is
automatically adjusted, in accordance with safety region 2 of the JEITA specification.
15 THMEN
Thermistor Enable Input. THMEN controls THMSW by connecting the external thermistor pullup resistor
and the thermistor monitoring circuit to LDO. Drive THMEN high to enable the thermistor circuit in
discharge mode and to connect the external thermistor pullup resistor. Drive THMEN low to disconnect
the external thermistor pullup resistor and to disable the thermistor monitoring circuit to conserve
battery energy when not charging.
16 THMSW
Thermistor Pullup Supply Switch. Drive THMEN high to enable the THMSW, shorting the THMSW output
to LDO. Drive THMEN low to open the THMSW switch. THMSW is always on when a valid input source
is present and the battery is being charged. When no input source is present, THMSW is controlled by
THMEN. THMSW is also active when the battery is being discharged, so that the battery temperature
can be monitored for an overtemperature condition.
13
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Pin Description (continued)
PIN NAME FUNCTION
17 LDO
Always-On Linear Regulator Output. LDO is the output of an internal always-on 3.3V LDO that provides
power to external circuitry. The LDO output provides up to 30mA of current for indicator LEDs or other
loads. LDO remains active even when only a battery is present, so that the thermistor monitor circuitry
can be activated when the battery is being discharged, and other circuitry can remain powered.
Connect a 1FF ceramic capacitor from LDO to GND.
18, 19 USB
USB Power Input. USB is capable of delivering up to 0.5A to SYS. The USB current limit is set with
PEN2 and USUS. See Table 2. Both USB pins must be connected together externally. Connect a 4.7FF
ceramic capacitor from USB to GND.
20, 21 BATT
Battery Connection. Connect the positive terminal of a single-cell Li+ battery to BATT. The battery
charges from SYS when a valid source is present at DC or USB. BATT powers SYS when neither DC nor
USB power is present, or when the SYS load exceeds the input current limit. Both BATT pins must be
connected together externally.
22 CHG Charger Status Output. The CHG active-low, open-drain output pulls low when the battery is in fast
charge or prequal. Otherwise, CHG is high impedance.
23, 24 SYS
System Supply Output. SYS is connected to BATT through an internal 40mI system load switch when
DC or USB are invalid, or when the SYS load is greater than the input current limit.
When a valid voltage is present at DC or USB, SYS is limited to or 4.35V. When the system load (ISYS)
exceeds the DC or USB current limit, SYS is regulated to 75mV below VBATT and both the input and the
battery service the SYS load. Bypass SYS to GND with a 10FF ceramic capacitor. Both SYS pins must
be connected together externally.
25 OT Battery Overtemperature Flag. The OT active-low, open-drain output pulls low when THMEN is high and
the battery temperature is R +75NC.
26 DOK DC Power-OK Output. The DOK active-low, open-drain output pulls low when a valid input is detected
at DC.
27 UOK USB Power-OK Output. The UOK active-low, open-drain output pulls low when a valid input is detected
at USB.
28 FLT Fault Output. The FLT active-low, open-drain output pulls low when the battery timer expires before
prequal or fast charge complete.
— EP Exposed Pad. Connect the exposed pad to GND. Connecting the exposed pad does not remove the
requirement for proper ground connections to the appropriate pins.
14
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 1. Block Diagram
SET INPUT
LIMIT
VL LDO FOR
IC POWER
CURRENT-
LIMITED VOLTAGE
REGULATOR
THERMISTOR
MONITOR
(SEE FIGURE 5)
CHARGE
TERMINATION
AND MONITOR
PWR OK
DC
DC
DOK
VL
USB
UOK
PEN1
PEN2
USUS
PSET
GND EP
DC POWER MANAGEMENT
Li+ BATTERY CHARGER
AND SYS LOAD SWITCH
SYS
T
SYS
LDOOT
ISET
BATT
BATT
THM
THMSW
THMEN
CT
CHG
SET INPUT
LIMIT
CURRENT-
LIMITED VOLTAGE
REGULATOR
INPUT AND
CHARGER
CURRENT-LIMIT
LOGIC CONTROL
CHARGER
CURRENT AND
VOLTAGE
CONTROL
THERMAL
REGULATION
PWR OK
USB POWER MANAGEMENT
3.3V ALWAYS-ON
LOW-IQ LDO
CHARGE
TIMER
MAX8934G
CEN
FLT
DONE
CHG
15
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 2. Typical Application Circuit Using Separate DC and USB Connector
DC
CHARGE
DONE
ADAPTER
RPU
1MIRPU
4x 1MI
CDC
10FF
CSYS
10FF
CBATT
4.7FF
CUSB
4.7FF
CLDO
1FF
DC
PEN1
PEN2
PSET
VL
GND
CT
THMSW
THMSW
ACTIVE
DISABLED
THM
THMEN
CEN
DONE
FLT
UOK
DOK
TO LDO
LDO
OVERTEMPERATURE
FAULT OUTPUT
USB PWR OK
DC PWR OK
TO
SYSTEM
LOAD
CHARGE
INDICATOR
1-CELL
Li+
SYS
SYS
CHG
BATT
BATT
USB
USB
LDO
USUS
EP
OT
1
2
3
4
OFF
CHARGE ON
500mA
100mA
6
7
8
9, 13
10
15
16
14
5
12
17
19
USB SUSPEND
18
21
20
22
24
23
26
27
28
25
RPSET
1.5kI
1MI
ISET
11
RISET
3kI
100kINTC
100kI
25C
CVL
0.1FF
CCT
0.068FF
MAX8934G
VBUS
D-
D+
ID
GND
2
1
3
4
5
16
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 3. Typical Application Circuit Using a 5-Pin USB Connector or Other DC/USB Common Connector
DC
CHARGE
DONE
5-PIN USB
CONNECTOR
RPU
1MI
RPU
4x 1MI
CDC
10FF
CSYS
10FF
CBATT
4.7FF
CLDO
1FF
DC
PSET
VL
GND
CT
THMSW
THMSW
ACTIVE
DISABLED
THM
THMEN
DONE
FLT
UOK
DOK
TO LDO
VLDO
OVERTEMPERATURE
FAULT OUTPUT
USB PWR OK
DC PWR OK
TO
SYSTEM
LOAD
CHARGE
INDICATOR
1-CELL
Li+
SYS
SYS
CHG
BATT
BATT
USB
USB
LDO
USUS
EP
OT
1
2
3
CEN
5
OFF
CHARGE ON
DC
VBUS
D-
D+
ID
GND
USB
PEN2
PEN1
500mA
100mA
6
7
8
9, 13
10
15
16
14
4
1
2
3
4
5
12
17
19
USB SUSPEND
18
21
20
22
24
23
26
27
28
25
RPSET
1.5kI
1MI
ISET
11
RISET
3kI
100kINTC
100kI
25C
CVL
0.1FF
CCT
0.068FF
MAX8934G
17
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Detailed Description
The MAX8934G is a dual-input linear charger with Smart
Power Selector that safely charges a single Li+/Li-Poly cell
in accordance with JEITA specifications. The MAX8934G
integrates power MOSFETs and control circuitry to manage
power flow in portable devices. See Figure 1. The charger
has two power inputs, DC and USB. These can be sepa-
rately connected to an AC adapter output and a USB port,
or the DC input could be a single power input that connects
to either an adapter or USB. Logic inputs, PEN1 and PEN2,
select the correct current limits for two-input or single-input
operation. Figure 2 is the typical application circuit using
separate DC and USB connectors. Figure 3 is the typical
application circuit using a 5-pin USB connector or another
DC/USB common connector.
In addition to charging the battery, the MAX8934G also
supplies power to the system through the SYS output. The
charging current is also provided from SYS so that the set
input current limit controls the total SYS current, where total
SYS current is the sum of the system load current and the
battery-charging current. SYS is powered from either the
DC input pin or the USB input pin. If both the DC and USB
sources are connected, DC takes precedence.
In some instances, there may not be enough adapter
current or USB current to supply peak system loads. The
MAX8934G Smart Power Selector circuitry offers flexible
power distribution from an AC adapter or USB source to
the battery and system load. The battery is charged with
any available power not used by the system load. If a
system load peak exceeds the input current limit, supple-
mental current is taken from the battery. Thermal limiting
prevents overheating by reducing power drawn from the
input source.
The MAX8934G features an overvoltage limiter at SYS. If
the DC or USB input voltage exceeds the SYS regulation
voltage, VSYS does not follow VDC or VUSB, but remains
at its regulation voltage. The MAX8934G has numerous
other charging and power-management features that are
detailed in the following sections.
A 3.3V ultra-low quiescent current, always-on LDO pro-
vides up to 30mA for indicator LEDs and for backup
power to the system. This LDO powers the thermistor
monitor circuitry and provides bias to the external pullup
resistor for the thermistor.
Table 1. External Components List for Figures 2 and 3
COMPONENT
(Figures 2 and 3) FUNCTION PART NUMBER
CDC DC filter capacitor 10FF ±10%, 16V X5R ceramic capacitor (0805)
Taiyo Yuden EMK212BJ106KG
CUSB USB filter capacitor 4.7FF ±10%, 10V X5R ceramic capacitor (0805)
Taiyo Yuden LMK212BJ475KD
CVL VL filter capacitor 0.1FF ±10%, 10V X5R ceramic capacitor (0402)
Taiyo Yuden LMK105BJ104KV
CSYS SYS output bypass capacitors 10FF ±10%, 6.3V X5R ceramic capacitor (0805)
Taiyo Yuden JMK212BJ106KD
CBATT Battery bypass capacitor 4.7FF ±10%, 6.3V X5R ceramic capacitor (0805)
Taiyo Yuden JMK212BJ475KD
CCT Charger timing capacitor 0.068FF ±10%, 16V X5R ceramic capacitor (0402)
Taiyo Yuden EMK105BJ683KV
CLDO LDO output capacitor 1FF ±10%, 6.3V X5R ceramic capacitor (0402)
Taiyo Yuden JMK105BJ105KV
RPU (x5) Logic-output pullup resistors 1MI ±5% resistor
THM Negative TC thermistor Vishay NTC Thermistor P/N NTHS0603N01N1003FF
RTHMSW THM pullup resistor 100kI
RPSET DC input current-limit programming resistor 1.5kI ±1% for 2A limit
RISET Fast-charge current programming resistor 3kI ±1% for 1A charging
18
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Smart Power Selector
The MAX8934G Smart Power Selector seamlessly dis-
tributes power among the external inputs, the battery,
and the system load (see the Typical Operating Circuit).
The basic functions performed are:
U With both an external power supply (USB or adapter)
and battery connected:
U When the system load requirements are less than
the input current limit, the battery is charged with
residual power from the input.
U When the system load requirements exceed the
input current limit, the battery supplies supplemen-
tal current to the load.
U When the battery is connected and there is no external
power input, the system is powered from the battery.
U When an external power input is connected and there
is no battery, the system is powered from the external
power input.
System Load Switch
An internal 40mI MOSFET connects SYS to BATT (Q3
in the Typical Operating Circuit) when no voltage source
is available at DC or USB. When an external source is
detected at DC or USB, this switch is opened and SYS
is powered from the valid input source through the input
limiter.
The SYS-BATT switch also holds up SYS when the system
load exceeds the input current limit. If that should happen,
the SYS-BATT switch turns on so that the battery supplies
additional SYS load current. If the system load continu-
ously exceeds the input current limit, the battery does not
charge, even though external power is connected. This is
not expected to occur in most cases, since high loads usu-
ally occur only in short peaks. During these peaks, battery
energy is used, but at all other times the battery charges.
Input Limiter
The input voltage limiter is essentially an LDO regula-
tor. While in dropout, the regulator dissipates a small
I2R loss through the 0.2I MOSFET (Q1 in the Typical
Operating Circuit) between DC and SYS. With an AC
adapter or USB source connected, the input limiter
distributes power from the external power source to the
system load and battery charger. In addition to the input
limiter’s primary function of passing power to the system
and charger loads at SYS, it performs several additional
functions to optimize use of available power.
Input Voltage Limiting
If an input voltage is above the overvoltage threshold
(6.9V typ), the MAX8934G enters overvoltage lockout
(OVLO). OVLO protects the MAX8934G and downstream
circuitry from high-voltage stress up to 14V at DC and
8V at USB. In OVLO, VL remains on, the input switch that
sees overvoltage (Q1, Q2, Typical Operating Circuit)
opens, the appropriate power-monitor output (DOK,
UOK) is high impedance, and CHG is high impedance.
If both DC and USB see overvoltage, both input switches
(Q1 and Q2, Typical Operating Circuit) open and the
charger turns off. The BATT-to-SYS switch (Q3, Typical
Operating Circuit) closes, allowing the battery to power
SYS. An input is also invalid if it is less than BATT, or less
than the DC undervoltage threshold of 3.5V (falling). With
an invalid input voltage, SYS connects to BATT through a
40mI switch (Q3, Typical Operating Circuit).
Input Overcurrent Protection
The current at DC and USB is limited to prevent input
overload. This current limit can be selected to match the
capabilities of the source, whether it is a 100mA or 500mA
USB source, or an AC adapter. When the load exceeds
the input current limit, SYS drops to 75mV below BATT
and the battery supplies supplemental load current.
Thermal Limiting
The MAX8934G reduces input limiter current by 5%/NC
when its die temperature exceeds +100NC. The system
load (SYS) has priority over the charger current, so low-
ering the charge current first reduces the input current. If
the junction temperature still reaches +120NC in spite of
charge current reduction, no input (DC or USB) current
is drawn, the battery supplies the entire system load,
and SYS is regulated at 75mV below BATT. Note that
this on-chip thermal-limiting circuitry is not related to and
operates independently from the thermistor input.
Adaptive Battery Charging
While the system is powered from DC, the charger draws
power from SYS to charge the battery. If the charger
load plus system load exceeds the input current limit, an
adaptive charger control loop reduces charge current
to prevent the SYS voltage from collapsing. Maintaining
a higher SYS voltage improves efficiency and reduces
power dissipation in the input limiter. The total current
through the switch (Q1 or Q2 in the Typical Operating
Circuit) is the sum of the load current at SYS and the bat-
tery charging current. The MAX8934G limiter clamps at
4.35V, so input voltages greater than 4.35V can increase
power dissipation in the limiter. The MAX8934G input
19
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
limiter power loss is (VDC – VSYS) x IDC, where VSYS
may be as high as 4.35V. The input limiter power loss is
not less than 0.2I x IDC2. Also note that the MAX8934G
turns off when any input exceeds 6.9V (typ).
DC and USB Connections and
Current-Limit Options
Input Current Limit
The input and charger current limits are set as shown
in Table 2. It is often preferable to change the input
current limit as the input power source is changed. The
MAX8934G facilitates this by allowing different input cur-
rent limits for DC and USB as shown in Table 2.
When the input current limit is reached, the first action
taken by the MAX8934G is to reduce the battery charge
current. This allows the regulator to stay in dropout dur-
ing heavy loads, thus reducing power dissipation. If, after
the charge current is reduced to 0mA, the load at SYS
still exceeds the input current limit, SYS voltage begins
to fall. When the SYS voltage drops to BATT, the SYS-
to-BATT switch turns on, using battery power to support
the system load during the load peak. The MAX8934G
features flexible input connections (at the DC and USB
input pins) and current-limit settings (set by PEN1, PEN2,
PSET, and ISET) to accommodate nearly any input
power configuration. However, it is expected that most
systems use one of two external power schemes: sepa-
rate connections for USB and an AC adapter, or a single
connector that accepts either USB or AC adapter output.
Input and charger current limit are controlled by PEN1,
PEN2, RPSET, and RISET, as shown in Table 2.
Separate Adapter and USB Connectors
When the AC adapter and USB have separate connec-
tors, the adapter output connects to DC and the USB
source connects to USB. PEN1 is permanently connected
high (to DC or VL). The DC current limit is set by RPSET,
while the USB current limit is set by PEN2 and USUS.
Single Common Connector
for USB or Adapter
When a single common connector is used for both AC
adapter and USB sources, the DC input is used for
both input sources. The unused USB inputs should be
grounded when an AC adapter is connected at DC,
PEN1 should be pulled high to select the current limit
set by RPSET. When a USB source is connected, PEN1
should be low to select 500mA, 100mA, or USB suspend
(further selected by PEN2 and USUS). PEN1 can be
pulled up by the AC adapter power to implement hard-
ware adapter/USB selection.
USB Suspend
Driving USUS high when PEN1 is low turns off the char-
ger and reduces input current to 190FA to accommodate
USB suspend mode. The input limiter is disabled and
SYS is supported by BATT.
Power Monitor Outputs (UOK, DOK)
DOK is an open-drain output that pulls low when the DC
input has valid power. UOK is an open-drain output that
pulls low when the USB input has valid power. A valid
input for DC or USB is between 4.1V and 6.6V. If a single
power-OK output is preferred, DOK and UOK can be
wire-ORed together. The combined output then pulls low
if either USB or DC is valid.
Table 2. Input Limiter Control Logic
*Charge current cannot exceed the input current limit. Actual charge current may be less than the maximum charge current if the
total SYS load exceeds the input current limit.
POWER
SOURCE DOK UOK PEN1 PEN2 USUS DC INPUT
CURRENT LIMIT
USB INPUT
CURRENT LIMIT
MAXIMUM CHARGE
CURRENT*
AC adapter at
DC input L X H X X 3000V/RPSET USB input off;
DC input has
priority
3000V/RISET
USB power at
DC input
L X L H L 475mA 475mA
L X L L L 95mA 95mA
L X L X H USB suspend 0
USB power at
USB input; DC
unconnected
H L X H L
No DC input
475mA 3000V/RISET
H L X L L 95mA
H L X X H USB suspend 0
DC and USB
unconnected H H X X X No USB input 0
20
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Soft-Start
To prevent input transients that can cause instability in
the USB or AC adapter power source, the rate of change
of input current and charge current is limited. When a
valid DC or USB input is connected, the input current
limit is ramped from zero to the set current-limit value (as
shown in Table 2). If DC is connected with no USB power
present, input current ramps in 1.5ms. If DC is con-
nected with USB already present, input current ramps in
50Fs. When USB is connected with no DC present, input
current also ramps in 50Fs. If USB is connected with DC
already present, the USB input is ignored.
If an adapter is plugged into DC while USB is already
powered, the input current limit reramps from zero back
up to the DC current limit so that the AC adapter does
not see a load step. During this transition, if the input
current limit is below the SYS load current, the battery
supplies the additional current needed to support the
load. Additionally, capacitance can be added to SYS to
support the load during input power transitions. When
the charger is turned on, charge current ramps from zero
to the ISET current value in 1.5ms. Charge current also
ramps when transitioning to fast-charge from prequal
and when changing the USB charge current from 100mA
to 500mA with PEN2. There is no dI/dt limiting, however,
if ISET is changed suddenly using a switch at RISET.
Battery Charger
The battery charger state diagram is illustrated in Figure
7. With a valid DC or USB input, the battery charger
initiates a charge cycle when the charger is enabled. It
first detects the battery voltage. If the battery voltage is
less than the BATT prequal threshold (3.0V), the charger
enters prequal mode and charges the battery at 20% of
the maximum fast-charge current. This reduced charge
rate ensures that the maximum fast-charge current set-
ting does not damage a deeply discharged battery.
Once the battery voltage rises to 3.0V, the charger tran-
sitions to fast-charge mode and applies the maximum
charge current. As charging continues, the battery volt-
age rises until it approaches the battery regulation volt-
age where charge current starts tapering down. When
charge current decreases to 20% of the fast-charge
current, the charger enters a brief 15s top-off state, then
DONE pulls low and charging stops. If the battery volt-
age subsequently drops below the recharge threshold,
charging restarts and the timers reset.
Charge Enable (CEN)
When CEN is low, the charger is on. When CEN is high,
the charger turns off. CEN does not affect the SYS out-
put. In many systems, there is no need for the system
controller (typically a microprocessor) to disable the
charger, because the MAX8934G Smart Power Selector
circuitry independently manages charging and adapter/
battery power hand-off. In these situations, CEN can be
connected to ground.
Setting the Charge Current
ISET adjusts charge current to match the capacity of the
battery. A resistor from ISET to ground sets the maximum
fast-charge current:
ICHGMAX = 2000 x 1.5V/RISET = 3000V/RISET
Determine the ICHGMAX value by considering the char-
acteristics of the battery. It is not necessary to limit the
charge current based on the capabilities of the expected
AC adapter/USB charging input, the system load, or
thermal limitations of the PCB. The MAX8934G automati-
cally adjusts the charging algorithm to accommodate
these factors.
Monitoring the Charge Current
In addition to setting the charge current, ISET can also
be used to monitor the actual current charging the bat-
tery. See Figure 4. The ISET output voltage is:
VISET = ICHG x 1.5V/ICHGMAX = ICHG x RISET/2000
where ICHGMAX is the set fast-charge current and ICHG
is the actual battery charge current. A 1.5V output indi-
cates the battery is being charged at the maximum set
fast charge current; 0V indicates no charging. This volt-
age is also used by the charger control circuitry to set
and monitor the battery current. Avoid adding more than
10pF capacitance directly to the ISET pin. If filtering of
the charge-current monitor is necessary, add a resistor
of 100kI or more between ISET and the filter capacitor
to preserve charger stability.
Note that the actual charge current can be less than the
set fast-charge current when the charger enters voltage
mode or when the input current limiter or thermal limiter
reduces charge current. This prevents the charger from
overloading the input source or overheating the system.
Charge Termination
When the charge current falls to the termination threshold
and the charger is in voltage mode, charging is com-
plete. Charging continues for a brief 15s top-off period
and then enters the DONE state where charging stops.
The DONE current threshold (IDONE) is set to 20% of the
21
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
fast-charge current setting. Note that if charge current
falls to IDONE as a result of the input or thermal limiter,
the charger does not enter the DONE state. For the char-
ger to enter the DONE state, the charge current must be
less than IDONE, the charger must be in voltage mode,
and the input or thermal limiter must not be reducing the
charge current. The charger exits the DONE state, and
fast-charge resumes if the battery voltage subsequently
drops 104mV or if CEN is cycled.
Charge Status Outputs
Charge Output (CHG)
CHG is an open-drain, active-low output that is low dur-
ing charging. CHG is low when the battery charger is in
its prequalification and fast-charge states. When charge
current falls to the charge termination threshold (IDONE)
and the charger is in voltage mode, CHG goes high
impedance. CHG goes high impedance if the thermistor
causes the charger to enter temperature suspend mode.
When the MAX8934G is used with a microprocessor (FP),
connect a pullup resistor between CHG and the logic I/O
voltage to indicate charge status to the FP. Alternatively,
CHG can sink up to 20mA for an LED indicator.
Charge DONE Output (DONE)
DONE is an open-drain, active-low output that goes
low when charging is complete. The charger enters its
DONE state 15s after the charge current falls to the
charge-termination threshold (IDONE) and the charger is
in voltage mode. The charger exits the DONE state, and
fast-charge resumes, if the battery voltage subsequently
drops 104mV, or if input power or CEN is cycled. When
the MAX8934G is used in conjunction with a FP, con-
nect a pullup resistor between DONE and the logic I/O
voltage to indicate charge status to the FP. Alternatively,
DONE can sink up to 20mA for an LED indicator.
Fault Output (FLT) and Charge Timer
FLT is an open-drain, active-low output that goes low
during a battery fault. The fault state occurs when either
the prequal or fast-charge timer expires. The prequal
and fast-charge fault timers are set by CCT:
CT
PQ
C
PREQUAL: t 180min 0.068 F
= × F
CT
FC
C
FAST CHARGE: t 300min 0.068 F
= × F
TO
TOP OFF:t 15s−=
While in fast-charge mode, a large system load or device
self-heating can cause the MAX8934G to reduce charge
current. Under these circumstances, the fast-charge
timer adjusts to ensure that adequate charge time is still
allowed. Consequently, the fast-charge timer is slowed
by 2x if charge current is reduced below 50% of the pro-
grammed fast-charge level. If charge current is reduced
to below 20% of the programmed level, the fast-charge
timer is paused. The fast-charge timer is not adjusted
if the charger is in voltage mode where charge current
reduces due to current tapering under normal charging.
To exit a fault state, toggle CEN or remove and reconnect
the input source(s). Note also that thermistor out of range
or on-chip thermal-limit conditions are not considered
faults. When the MAX8934G is used in conjunction with a
FP, connect a pullup resistor between FLT and the logic
I/O voltage to indicate fault status to the FP. Alternatively,
FLT can sink up to 20mA for an LED indicator.
Thermistor Monitor
The MAX8934G thermistor monitor is configured to
execute JEITA recommendations regarding Li+/Li-Poly
battery charging by adjusting the fast charge current
and/or the charge termination voltage accordingly (see
Figure 6 ). Connect the THM input to an external negative
temperature coefficient (NTC) thermistor to monitor bat-
tery or system temperature. Since the thermistor monitor-
ing circuit employs an external bias resistor from THM
to THMSW, the thermistor is not limited only to 10kI (at
Figure 4. Monitoring the Battery Charge Current with VISET
1.5
VISET
0
02000 (1.5V/RISET)
BATTERY CHARGING CURRENT (A)
MONITORING THE BATTERY
CHARGE CURRENT WITH VISET
DISCHARGING
VISET (V)
22
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
+25NC). Any thermistor resistance can be used as long
as the value of RTHMSW is equivalent to the thermistor’s
+25NC resistance. The MAX8934G THM thresholds are
optimized for a thermistor Beta of 3964. The general rela-
tion of thermistor resistance to temperature is defined by
the following equation:
11
-
T 273 C 298 C
T 25
RR e
+° °
β
= ×
where:
RT = The resistance in ohms of the thermistor at
temperature T in NC
R25 = The resistance in ohms of the thermistor at
+25NC
A = The material constant of the thermistor
T = The temperature of the thermistor in NC
Charging is suspended when the thermistor temperature
is out of range (VTHM_T1 < VTHM or VTHM < VTHM_T4).
The charge timers are also suspended and hold their
state but no fault is indicated. When the thermistor
comes back into range, charging resumes and the
charge timer continues from where it left off.
The THMEN input controls THMSW and the thermistor
monitor circuitry when the battery charger is disabled,
providing the user with the means to minimize the bat-
tery current drain caused by the thermistor monitor. The
THMEN input is ignored while the battery is charging,
since the thermistor must be monitored at all times.
While charging, the thermistor monitor is used to auto-
matically adjust the charge termination voltage and/or
the fast-charge current, depending on the sensed bat-
tery temperature. If the battery temperature exceeds the
THM hot overtemperature threshold and THMEN is high,
the OT flag pulls low. Typical systems connect OT to a
FP input so that the system can safely shut down.
Always-On LDO
The ultra-low quiescent current LDO is always on and is
preset to an output voltage of 3.3V. The LDO provides up
to 30mA output current. When DC and USB are invalid
and the battery is discharging, the LDO output volt-
age tracks VSYS as it drops below 3.3V. A 1FF ceramic
capacitor connected from LDO to GND is recommended
for most applications.
Power Dissipation
PCB Layout and Routing
Good design minimizes ground bounce and voltage
gradients in the ground plane. GND should connect to
the power-ground plane at only one point to minimize the
effects of power-ground currents. Battery ground should
connect directly to the power-ground plane. Connect
GND to the exposed pad directly under the IC. Use mul-
tiple tightly spaced vias to the ground plane under the
exposed pad to help cool the IC. Position input capaci-
tors from DC, SYS, BATT, and USB to the power-ground
plane as close as possible to the IC. Keep high current
traces such as those to DC, SYS, and BATT as short and
wide as possible. Refer to the MAX8934A Evaluation Kit
for a suitable PCB layout example.
Table 3. Package Thermal Characteristics
28-PIN 4mm x 4mm THIN QFN
SINGLE-LAYER PCB MULTILAYER PCB
Continuous Power
Dissipation
1666.7mW
(derate 20.8mW/NC above +70NC)
2285.7mW
(derate 28.6mW/NC above +70NC)
BJA 48NC/W 35NC/W
BJC 3NC/W 3NC/W
23
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 5. Thermistor Monitor Details
T
CHG
SYS
LDO
VINT
CHG
VINT
THERMISTOR
MONITOR
CHARGER
CONTROL
CHG
OT
T4
(60NC)
T3
(45NC)
T2
(10NC)
TOT
(75NC)
T1
(0NC)
-
+
VINT
CHG
-
+
VINT
VINT
THM
THMSW
THMEN
RTHMSW
VINT
CHG
CHG
+
-
VINT
VINT
THMEN
NOT CHARGING
-
+
VINT
VINT
+
-
CHG
LOW-IQ, ALWAYS-ON 3.3V LDO
TRACKS SYS WHEN DC AND USB ARE NOT
PRESENT, THE BATTERY IS BEING
DISCHARGED, AND VBATT P 3.3V.
24
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 6. Safety Region 2: Fast-Charge Currents and Charge Termination Voltages
TEMPERATURE (NC)
TEMPERATURE (NC)
0
4.2
T1 T2 T3 T4
T1 T2 T3 T4
4.1
4.075
4.0
0.5C
C
10 25 45 60
010 25 45 60
85
85
BATT REGULATION VOLTAGE (V)
(VBATT_REG)
FAST-CHARGE CURRENT
(ICHG)
25
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Figure 7. Charger State Diagram
STATE DIAGRAM IS FOR 10NC < TEMP < +45NC,
OUTSIDE OF THIS RANGE SEE FIGURE 6
VBATT < 2.82V
RESET TIMER
ICHG > IDONE
RESET TIMER
VBATT < 4.1V
RESET TIMER
ICHG < IDONE
AND VBATT = 4.2V
AND THERMAL
OR OUTPUT LIMIT
NOT EXCEEDED
RESET TIMER
ANY STATE
TIMER > tPQ
TIMER > 15s
VBATT < 2.82V,
RESET TIMER
VBATT > 3V,
RESET TIMER
VTHM > VTHM_OT VTHM < VTHM_OT
VTHM_T1 < VTHM < VTHM_T4
TIMER RESUME
VTHM_T1 < VTHM OR VTHM < VTHM_T4
TIMER SUSPEND
(PQ, FC, TOP-OFF)
ANY CHARGING
STATE
OVERTEMP
OT = LOW
UOK OR DOK = LOW
CEN = 0
RESET TIMER
NOT READY
UOK AND DOK = HIGH-Z
CHG = HIGH-Z
FLT = HIGH-Z
DONE = HIGH-Z
ICHG = 0mA
PREQUAL
UOK OR DOK = LOW
CHG = LOW
FLT = HIGH-Z
DONE = HIGH-Z
0V P VBATT P 3V
ICHG = ICHGMAX 10
FAST-CHARGE
UOK OR DOK = LOW
CHG = LOW
FLT = HIGH-Z
DONE = HIGH-Z
3V P VBATT P 4.2V
ICHG = ICHGMAX
TOP-OFF
UOK OR DOK = LOW
CHG = HIGH-Z
FLT = HIGH-Z
DONE = HIGH-Z
BATT = 4.2V
ICHG = IDONE
DONE
UOK OR DOK = LOW
CHG = HIGH-Z
FLT = HIGH-Z
DONE = LOW
4.1V < VBATT < 4.2V
ICHG = 0mA
TEMPERATURE
SUSPEND
ICHG = 0mA
UOK OR DOK = PREVIOUS STATE
CHG = HIGH-Z
FLT = HIGH-Z
DONE = HIGH-Z
CEN = HIGH
OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
TOGGLE CEN
OR REMOVE AND RECONNECT
THE INPUT SOURCE(S)
FAULT
UOK AND DOK = LOW
CHG = HIGH-Z
FLT = LOW
DONE = HIGH-Z
ICHG = 0mA
TIMER > tFC
(TIMER SLOWED BY 2X IF
ICHG < ICHGMAX/2, AND
PAUSED IF ICHG < ICHGMAX/5
WHILE BATT < 4.2V)
26
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Chip Information
PROCESS: BiCMOS
Pin Configuration
MAX8934G
THIN QFN
TOP VIEW
26
27
25
24
10
9
11
DC
CEN
PEN1
PEN2
PSET
12
DONE
BATT
USB
LDO
BATT
THMSW
THMEN
1
*EP
*EXPOSED PAD
2
OT
4567
2021 19 17 16 15
DOK
UOK
USUS
ISET
CT
GND
DC USB
3
18
28 8
FLT VL
SYS
23 13 GND
SYS
22 14 THM
CHG
27
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Package Information
For the latest package outline information and land patterns, go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-”
in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to
the package regardless of RoHS status.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
28 TQFN-EP T2844+1 21-0139 90-0068
28
Maxim Integrated
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Package Information (continued)
For the latest package outline information and land patterns, go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-”
in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to
the package regardless of RoHS status.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and
max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 29
© 2010 Maxim Integrated Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
Dual-Input Linear Charger, Smart Power Selector
with Advanced Battery Temperature Monitoring
MAX8934G
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION DATE PAGES
CHANGED
0 6/10 Initial release —
