General Description
The MAX3097E/MAX3098E feature three high-speed RS-
485/RS-422 receivers with fault-detection circuitry and
fault-status outputs. The receivers’ inputs have fault
thresholds that detect when the part is not in a valid state.
The MAX3097E/MAX3098E indicate when a receiver
input is in an open-circuit condition, short-circuit condi-
tion, or outside the common-mode range. They also
generate a fault indication when the differential input
voltage goes below a preset threshold. See Ordering
Information or the Electrical Characteristics for thresh-
old values.
The fault circuitry includes a capacitor-programmable
delay to ensure that there are no erroneous fault condi-
tions even at slow edge rates. Each receiver is capable
of accepting data at rates up to 32Mbps.
________________________Applications
RS-485/RS-422 Receivers for Motor-Shaft
Encoders
High-Speed, Triple RS-485/RS-422 Receiver with
Extended Electrostatic Discharge (ESD)
Triple RS-485/RS-422 Receiver with Input Fault
Indication
Telecommunications
Embedded Systems
Features
♦Detects the Following RS-485 Faults:
Open-Circuit Condition
Short-Circuit Condition
Low Differential Voltage Signal
Common-Mode Range Violation
♦ESD Protection
±15kV—Human Body Model
±15kV—IEC 1000-4-2, Air-Gap Discharge
Method
±8kV—IEC 1000-4-2, Contact Discharge Method
♦Single +3V to +5.5V Operation
♦-10V to +13.2V Extended Common-Mode Range
♦Capacitor-Programmable Delay of Fault Indication
Allows Error-Free Operation at Slow Data Rates
♦Independent and Universal Fault Outputs
♦32Mbps Data Rate
♦16-Pin QSOP is 40% Smaller than Industry-
Standard 26LS31/32 Solutions
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
________________________________________________________________ Maxim Integrated Products 1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
AV
CC
ALARMA
OUTA
ALARMB
OUTB
ALARMZ
OUTZ
ALARMD
TOP VIEW
MAX3097E
MAX3098E
QSOP/SO/DIP
A
B
Z
B
Z
GND
DELAY
Pin Configuration
ENCODED SIGNALS
A, A, B, B, Z, Z
MOTOR DRIVER
MOTOR
MOTOR
CONTROLLER
ALARM
OUTPUTS
RECEIVER
OUTPUTS
DSP
8
MAX3097E
MAX3098E
MAX547
12-BIT D/A
Typical Application Circuit
19-1727; Rev 0; 7/00
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Ordering Information
PART TEMP. RANGE PIN-
PACKAGE
MAX3097ECEE 0°C to +70°C 16 QSOP
MAX3097ECSE 0°C to +70°C 16 SO
Ordering Information continued at end of data sheet.
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = +3V to +5.5V, TA= TMIN to TMAX , unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
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.
Supply Voltage (VCC).............................................................+7V
Receiver Input Voltage (A, A, B, B, Z, Z) .............................±25V
Output Voltage (OUT_, ALARM_)...............-0.3V to (VCC + 0.3V)
DELAY ........................................................-0.3V to (VCC + 0.3V)
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW
16-Pin SO (derate 8.7mW/°C above +70°C).................696mW
16-Pin Plastic DIP (derate 10.53mW/°C
above +70°C).............................................................762mW
Operating Temperature Ranges
MAX3097EC_E...................................................0°C to +70°C
MAX3098E_C_E.................................................0°C to +70°C
MAX3097E_E_E ..............................................-40°C to +85°C
MAX3098E_E_E ..............................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range VCC 3 5.5 V
Supply Current ICC No load 3.1 4.0 mA
Receiver Differential Threshold
Voltage (Note 1) VTH -10V ≤ VCM ≤ 13.2V -200 +200 mV
Receiver Input Hysteresis ∆VTH -10V ≤ VCM ≤ 13.2V 40 mV
VCC = 4.75V, IO = -4mA, VID = 200mV VCC - 1.5
Output High Voltage VOH VCC = 3.0V, IO = -1mA, VID = 200mV VCC - 1.0 V
VCC = 4.75V, IO = +4mA, VID = -200mV 0.4
Output Low Voltage VOL VCC = 3.0V, IO = +1mA, VID = -200mV 0.4 V
Receiver Input Resistance RIN -10V ≤ VCM ≤ 13.2V 90 160 kΩ
VIN = 13.2V
(Note 2) 0.07 0.14
Input Current
(A , A , B , B (Z , Z ) IIN VCC = 0 or 5.5V VIN = -10V
(Note 2) -0.05 -0.11
mA
Output Short-Circuit Current IOSR 0 ≤ VRO ≤ VCC ±105 mA
FAULT DETECTION
FDIFH High limit 275 475
MAX3097E Fault-Detection
Receiver Differential Threshold
Voltage (Note 3) FDIFL
VCM = 0
Low limit -475 -275
mV
FDIFH High limit 0.12 0.20
MAX3098EA Fault-Detection
Receiver Differential Threshold
Voltage (Note 3) FDIFL
VCM = 0
Low limit -0.20 -0.12
V
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +5.5V, TA= TMIN to TMAX , unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
SWITCHING CHARACTERISTICS
(VCC = +3V to +5.5V, VID = ±3.0V, TA= TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
VCC = 4.5V to 5.5V 75
Propagation Delay from Input to
Output tPLH, tPHL CL = 15pF,
Figures 1, 2 VCC = 3.0V to 3.6V 85 ns
Receiver Skew |tPLH - tPHL|t
SKEW CL = 15pF, Figures 1, 2 ±10 ns
Channel-to-Channel
Propagation Delay Skew CL = 15pF, Figures 1, 2 ±10 ns
Maximum Data Rate fMAX CL = 15pF, Figure 1 32 Mbps
FAULT DETECTION
tDFLH 15
Differential Fault Propagation
Delay to Output (Note 5) tDFHL
CLF = 15pF, Figures 1, 3
1.2
µs
MAX3097E (Note 6) 1.0
Minimum Differential Slew Rate
to Avoid False Alarm Output MAX3098E (Note 7) 0.33
V/µs
tCMFLH 15
Common-Mode Fault
Propagation Delay to Output
(Note 5) tCMFHL
CL = 15pF, Figures 1, 4
1.5
µs
Note 1: VCM is the common-mode input voltage. VID is the differential input voltage.
Note 2: VIN is the input voltage at pins A, A, B, B, Z, Z.
Note 3: A differential terminating resistor is required for proper function of open-circuit fault detection (see Applications Information).
Note 4: See Applications Information for a discussion of the receiver common-mode voltage range and the operating conditions for
fault indication.
Note 5: Applies to the individual channel immediate-fault outputs (ALARM_) and the general delayed-fault output (ALARMD) when
there is no external capacitor at DELAY.
Note 6: Equivalent pulse test: 1.3V / (tDFLH - tDFHL) ≥SRD.
Note 7: Equivalent pulse test: 0.62V / (tDFLH - tDFHL) ≥SRD.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
FDIFH High limit 70 250
MAX3098EB Fault-Detection
Receiver Differential Threshold
Voltage (Note 3) FDIFL
VCM = 0
Low limit -250 -70
mV
FCMH High limit 13.2
Fault-Detection Common-Mode
Voltage Range (Note 4) FCML Low limit -10 V
DELAY Current Source VCC = 5V, VDELAY = 0 9 10 11 µA
VCC = 3V 1.55 1.73 1.90
DELAY Threshold VCC = 5V 3.1 3.29 3.5 V
ESD PROTECTION
Human Body Model ±15
IEC1000-4-2 (Air-Gap Discharge) ±15
ESD Protection
(A, A, B, B, Z, Z)
IEC1000-4-2 (Contact Discharge) ±8
kV
DELAYED ALARM OUTPUT
MAX3097E/8E toc06
20µs/div
CH 1
CH 2
CH 3
GND
GND
GND
CH1: VA, 5V/div
CH2: VALARMA, 5V/div
CH3: VALARMD, 5V/div
VA = GND, CDELAY = 270pF
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
4 _______________________________________________________________________________________
Typical Operating Characteristics
(Typical values are at VCC = +5V and TA= +25°C.)
1
100
10
1000
10,000
110010 1000 10,000
ALARMD OUTPUT DELAY
vs. CAPACITANCE
MAX3097E/8Etoc01
CAPACITANCE (pF)
ALARMD OUTPUT DELAY (µs)
VCC = 5V
VCC = 3V
30
40
50
60
70
-40 0-20 20 40 60
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
MAX3097E/8E toc02
TEMPERATURE (°C)
RECEIVER PROPAGATION DELAY (ns)
80
VCC = 5.0V
VCC = 3.3V
0
1
3
2
4
5
SUPPLY CURRENT vs.
TEMPERATURE
MAX3097E/8E toc03
SUPPLY CURRENT (mA)
-40 0-20 20 40 60
TEMPERATURE (°C)
80
VCC = 5.0V
VCC = 3.3V
NO LOAD
0
0.5
1.0
1.5
2.0
2.5
3.5
3.0
4.5
4.0
5.0
-45 -35-40 -30 -25 -20 -15 -10 -5 0
RECEIVER OUTPUT LOW VOLTAGE
vs. OUTPUT CURRENT
MAX3097E/8E toc04
OUTPUT CURRENT (mA)
OUTPUT LOW VOLTAGE (V)
VCC = 5.0V
VCC = 3.3V
0
1
2
4
3
5
6
010515203025
RECEIVER OUTPUT HIGH VOLTAGE
vs. OUTPUT CURRENT
MAX3097E/8E toc05
OUTPUT CURRENT (mA)
OUTPUT HIGH VOLTAGE (V)
VCC = 5.0V
VCC = 3.3V
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
_______________________________________________________________________________________ 5
CH 3
CH 2
GND
CH 1
COMMON-MODE VOLTAGE FAULT
(HIGH SIDE)
MAX3097E/8E toc07a
2ms/div
CH1: VA + AC(60Hz), 10V/div
CH2: VOUTA, 5V/div
CH3: VALARMA, 5V/div
VCC = 3V
GND
GND
COMMON-MODE VOLTAGE FAULT
(LOW SIDE)
MAX3097E/8E toc07b
CH 3
CH 2
GND
CH 1
2ms/div
CH1: VA + AC(60Hz), 10V/div
CH2: VOUTA, 5V/div
CH3: VALARMA, 5V/div
VCC = 3V
GND
GND
Typical Operating Characteristics (continued)
(Typical values are at VCC = +5V and TA= +25°C.)
MAX3097E
LOW DIFFERENTIAL INPUT FAULT
MAX3097E/8E toc08
CH 2 GND
GND
CH 1
100µs/div
CH1: VA, 200mV/div
CH2: VALARMA, 5V/div
VA = GND
SLEW-RATE FAULT
MAX3097E/8E toc09
CH 2 GND
GND
CH 1
CH1: VA, 5V/div
CH2: VALARMA, 5V/div
SLEW RATE = 0.05V/µs
VA = GND
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
6 _______________________________________________________________________________________
PIN NAME FUNCTION
1 A Noninverting Receiver A Input
2AInverting Receiver A Input
3 B Noninverting Receiver B Input
4BInverting Receiver B Input
5 Z Noninverting Receiver Z Input
6ZInverting Receiver Z Input
7 GND Ground
8 DELAY
Programmable Delay Terminal. Connect a capacitor from DELAY to GND to set the
ALARMD output delay time. To obtain a minimum delay, leave DELAY unconnected. See
Capacitance vs. ALARMD Output Delay in the Typical Operating Characteristics.
9 ALARMD
Delayed Fault Output. This output is the logic OR of ALARMA, ALARMB, and ALARMZ.
Place a capacitor from the DELAY pin to GND to set the delay (see Setting Delay Time). A
high logic level indicates a fault condition on at least one receiver input pair. A low level on
this pin indicates no fault condition is present.
10 OUTZ
Z Receiver Output. If VZ - V
Z
≥ +200mV, OUTZ will be high. If VZ - V
Z
≤ -200mV, OUTZ will
be low. If Z or Z exceeds the receiver’s input common-mode voltage range, the ALARMZ
output will be high and OUTZ will be indeterminate.
11 ALARMZ Z Fault Output. When ALARMZ is high, OUTZ is indeterminate. Tables 1 and 2 show all the
possible states for which an alarm is set.
12 OUTB
B Receiver Output. If VB - V
B ≥ +200mV, OUTB will be high. If VB - V
B ≤ -200mV, OUTB will
be low. If B or B exceeds the input receiver’s common-mode voltage range, the ALARMB
output will be high and OUTB will be indeterminate.
13 ALARMB B Fault Output. When ALARMB is high, OUTB is indeterminate. Tables 1 and 2 show all the
possible states for which an alarm is set.
14 OUTA
A Receiver Output. If VA - V
A ≥ +200mV, OUTA will be high. If VA - V A
≤ -200mV, OUTA will
be low. If A or A exceeds the receiver’s input common-mode voltage range, the ALARMA
output will be high and OUTA will be indeterminate.
15 ALARMA A Fault Output. When ALARMA is high, OUTA is indeterminate. Tables 1 and 2 show all the
possible states for which an alarm is set.
16 VCC Power Supply
Pin Description
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
_______________________________________________________________________________________ 7
(FAULT OUTPUT)
ALARMA
OR
ALARMD
VA
CLF
CL
A
VID
VA
A
OUTA
Figure 1. Typical Receiver Test Circuit
+3V
VID OV OV RISE/FALL TIMES ≤2ns
VCC/2VCC/2
-3V
VOH
RO
VOL
tPHL
tPLH
Figure 2. Propagation Delay
OV
VID FDIFL
VCC/2VCC/2
-3.0V
+3.0V
FDIFH
VOH
ALARM OR ALARMD
VOL
tDFHL
tDFLH
Figure 3. Fault-Detection Timing
OV
VIN
FCMH
VCC/2
VCC/2
FCML
VOH
ALARM OR ALARMD
VOL
tCMFHL
tCMFLH
tCMFHL
tCMFLH
VCC/2
VCC/2
Figure 4. Common-Mode Fault Propagation Delay
Test Circuits and Waveforms
Detailed Description
The MAX3097E/MAX3098E feature high-speed, triple
RS-485/RS-422 receivers with fault-detection circuitry
and fault-status outputs. The fault outputs are active
push-pull, requiring no pull-up resistors. The fault cir-
cuitry includes a capacitor-programmable delayed
FAULT_ output to ensure that there are no erroneous
fault conditions even at slow edge rates (see Delayed
Fault Output). The receivers operate at data rates up to
32Mbps.
The MAX3097E/MAX3098E are designed for motor-
shaft encoders with standard A, B, and Z outputs (see
Using the MAX3097E/MAX3098E as Shaft Encoder
Receivers). The devices provide an alarm for open-cir-
cuit conditions, short-circuit conditions, data nearing
the minimum differential threshold conditions, data
below the minimum threshold conditions, and receiver
inputs outside the input common-mode range. Tables 1
and 2 are functional tables for each receiver.
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
8 _______________________________________________________________________________________
Note 1: ALARMD indicates fault for any receiver.
Note 2: Receiver output may oscillate with this differential input condition.
Note 3: See Applications Information for conditions leading to input range fault condition.
X = Don’t care
INPUTS OUTPUTS
VID
(DIFFERENTIAL
INPUT VOLTAGE)
COMMON-MODE
VOLTAGE OUT_ ALARM_
ALARMD
t ≥ DELAY
(NOTE 1)
FAULT CONDITION
≥0.475V 1 0 0 Normal Operation
<0.475V and ≥0.275V 1 Indeterminate Indeterminate Indeterminate
<0.275V and ≥0.2V 1 1 1 Low Input Differential Voltage
≤0.2V and ≥-0.2V Indeterminate
(Note 2) 1 1 Low Input Differential Voltage
≤-0.2V and >-0.275V 0 1 1 Low Input Differential Voltage
≤-0.275V and
>-0.475V 0 Indeterminate Indeterminate
≤-0.475V
≤13.2V and ≥-10V
000
Indeterminate
X <-10V or >+13.2V Indeterminate
(Note 3) 11
Outside Common-Mode
Voltage Range
INPUTS OUTPUTS
VID
(DIFFERENTIAL
INPUT VOLTAGE)
COMMON-MODE
VOLTAGE OUT_ ALARM_
ALARMD
t ≥ DELAY
(NOTE 1)
FAULT CONDITION
≥0.2V 1 0 0 Normal Operation
<0.2V and ≥0.12V Indeterminate Indeterminate Indeterminate Indeterminate
<0.12V and ≥ - 0.12V Indeterminate
(Note 2) 1 1 Low Input Differential Voltage
≤-0.12V and ≥ -0.2V Indeterminate Indeterminate Indeterminate Indeterminate
≤-0.2V
≤13.2V and ≥-
10V
0 0 0 Normal Operation
X<-10V or
>+13.2V
Indeterminate
(Note 3) 11
Outside Common-Mode Voltage
Range
Table 1. MAX3097E Alarm Function Table (Each Receiver)
Table 2. MAX3098EA Alarm Function Table (Each Receiver)
Note 1: ALARMD indicates fault for any receiver.
Note 2: Receiver output may oscillate with this differential input condition.
Note 3: See Applications Information for conditions leading to input range fault condition.
X = Don’t care; for B-grade functionality, replace VID input values in Table 2 with B-grade parameters from Electrical Characteristics.
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
_______________________________________________________________________________________ 9
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD
encountered during handling and assembly. The
MAX3097E/MAX3098E receiver inputs have extra pro-
tection against static electricity found in normal opera-
tion. Maxim’s engineers developed state-of-the-art
structures to protect these pins against ±15kV ESD
without damage. After an ESD event, the MAX3097E/
MAX3098E continue working without latchup.
ESD protection can be tested in several ways. The
receiver inputs are characterized for protection to the
following:
•±15kV using the Human Body Model
•±8kV using the Contact Discharge method specified
in IEC 1000-4-2 (formerly IEC 801-2)
•15kV using the Air-Gap Discharge method specified
in IEC 1000-4-2 (formerly IEC 801-2)
ESD Test Conditions
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Human Body Model
Figure 5a shows the Human Body Model, and Figure
5b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the device through a
1.5kΩresistor.
IEC 1000-4-2
Since January 1996, all equipment manufactured and/or
sold in the European community has been required to
meet the stringent IEC 1000-4-2 specification. The IEC
1000-4-2 standard covers ESD testing and performance
of finished equipment; it does not specifically refer to inte-
grated circuits. The MAX3097E/MAX3098E help you
design equipment that meets Level 4 (the highest level)
of IEC 1000-4-2, without additional ESD-protection com-
ponents.
The main difference between tests done using the
Human Body Model and IEC 1000-4-2 is higher peak
current in IEC 1000-4-2. Because series resistance is
lower in the IEC 1000-4-2 ESD test model (Figure 6a), the
ESD-withstand voltage measured to this standard is gen-
erally lower than that measured using the Human Body
Model. Figure 6b shows the current waveform for the
±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test.
The Air-Gap test involves approaching the device with a
charge probe. The Contact Discharge method connects
the probe to the device before the probe is energized.
Machine Model
The Machine Model for ESD testing uses a 200pF stor-
age capacitor and zero-discharge resistance. It mimics
the stress caused by handling during manufacturing
and assembly. All pins (not just RS-485 inputs) require
this protection during manufacturing. Therefore, the
Machine Model is less relevant to the I/O ports than are
the Human Body Model and IEC 1000-4-2.
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC
1MΩ
RD
1.5k
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 5a. Human Body ESD Test Model
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPERES
Figure 5b. Human Body Model Current Waveform
___________Applications Information
Using the MAX3097E/MAX3098E as Shaft
Encoder Receivers
The MAX3097E/MAX3098E are triple RS-485 receivers
designed for shaft encoder receiver applications. A
shaft encoder is an electromechanical transducer that
converts mechanical rotary motion into three RS-485
differential signals. Two signals, A (A and A) and B (B
and B) provide incremental pulses as the shaft turns,
while the index signal, Z (Z and Z) occurs only once
per revolution to allow synchronization of the shaft to a
known position. Digital signal processing (DSP) tech-
niques are used to count the pulses and provide feed-
back of both shaft position and shaft velocity for a
stable positioning system.
Shaft encoders typically transmit RS-485 signals over
twisted-pair cables since the signal often has to travel
across a noisy electrical environment (Figure 7).
Detecting Faults
Signal integrity from the shaft encoder to the DSP is
essential for reliable system operation. Degraded sig-
nals could cause problems ranging from simple mis-
counts to loss of position. In an industrial environment,
many problems can occur within the three twisted
pairs. The MAX3097E/MAX3098E can detect various
types of common faults, including a low-input-level sig-
nal, open-circuit wires, short-circuit wires, and an input
signal outside the common-mode input voltage range
of the receiver.
Detecting Short Circuits
In Figure 8, if wires A and Aare shorted together, then A
and Awill be at the same potential, so the difference in
the voltage between the two will be approximately 0. This
causes fault A to trigger since the difference between A -
Ais less than the differential fault threshold.
Detecting Open-Circuit Conditions
Detecting an open-circuit condition is similar to detect-
ing a short-circuit condition and relies on the terminat-
ing resistor being across A and A. For example, if the
wire drops out of the Aterminal, A pulls Athrough the
terminating resistor to look like the same signal. In this
condition, VID is approximately 0 and a fault occurs.
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
10 ______________________________________________________________________________________
CHARGE-CURRENT
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
150pF
RC
50MΩ to 100MΩ
RD
330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
tr = 0.7ns to 1ns 30ns
60ns
t
100%
90%
10%
I
PEAK
I
A
A
B
B
Z
Z
Figure 7. Typical Shaft Encoder Output
Figure 6a. IEC 1000-4-2 ESD Test Model
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
______________________________________________________________________________________ 11
Common-Mode Range
The MAX3097E/MAX3098E contain circuitry that de-
tects if the input stage is going outside its useful com-
mon-mode range. If the received data could be
unreliable, a fault signal is triggered.
Detecting Low Input Differential
Due to cable attenuation on long wire runs, it is possi-
ble that VID < 200mV, and incorrect data will be
received. In this condition, a fault will be indicated.
Delayed Fault Output
The delayed fault output provides a programmable
blanking delay to allow transient faults to occur without
triggering an alarm. Such faults may occur with slow
signals triggering the receiver alarm through the zero
crossover region.
Figure 9 shows the delayed alarm output.
ALARMD performs a logic OR of ALARMA, ALARMB,
and ALARMZ (Figure 10). A NOR gate drives an N-
channel MOSFET so that in normal operation with no
faults, the current source (10µA typ) is shunted to
ground. Upon activation of any alarm from receiver A,
B, or Z, the MOSFET is turned off, allowing the current
source to charge CDELAY. When VDELAY exceeds the
DELAY threshold, the comparator output, ALARMD,
goes high. ALARMD is reset when all receiver alarms
go low, quickly discharging CDELAY to ground.
Setting Delay Time
ALARMD’s delay time is set with a single capacitor
connected from DELAY to GND. The delay comparator
threshold varies with supply voltage, and the CDELAY
value can be determined for a given time delay period
from the Capacitance vs. ALARMD Output Delay graph
in the Typical Operating Characteristics or using the
following equations:
tD= 15 + 0.33 x CDELAY (for VCC = 5V)
and
tD= 10 + 0.187 x CDELAY (for VCC = 3V)
where tDis in µs and CDELAY is in pF.
ALARMA
ALARMB
ALARMD
tDtD
ALARMA
ALARMB
ALARMZ
ALARMD
DELAY
COMPARATOR
NMOS
DELAY
CURRENT
SOURCE
CDELAY*
(EXTERNAL)
G1
DELAY THRESHOLD
tDLY
ALARM_
DELAY
ALARMD
*The capacitor (CDELAY) charges up slowly, but discharges rapidly.
If the duration of an ALARM_ pulse is less than tDLY, no alarm
output will be present at ALARMD.
Figure 9. Delayed Alarm Output Figure 10. ALARMD Simplified Schematic
Figure 8. Short-Circuit Detection
A
NORMAL OPERATION SHORT CIRCUIT A TO A
A
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
12 ______________________________________________________________________________________
Functional Diagram
A
A
B
B
Z
Z
ALARMA
OUTA
ALARMB
OUTB
ALARMZ
OUTZ
ALARMD
DELAY
GND
VCC
MAX3097E
MAX3098E
Chip Information
TRANSISTOR COUNT: 675
PROCESS: CMOS
Ordering Information (continued)
PART TEMP. RANGE PIN-
PACKAGE
MAX3097ECPE 0°C to +70°C 16 Plastic DIP
MAX3097EEEE -40°C to +85°C 16 QSOP
MAX3097EESE -40°C to +85°C 16 SO
MAX3097EEPE -40°C to +85°C 16 Plastic DIP
MAX3098EACEE 0°C to +70°C 16 QSOP
MAX3098EACSE 0°C to +70°C 16 SO
MAX3098EACPE 0°C to +70°C 16 Plastic DIP
MAX3098EAEEE -40°C to +85°C 16 QSOP
MAX3098EAESE -40°C to +85°C 16 SO
MAX3098EAEPE -40°C to +85°C 16 Plastic DIP
MAX3098EBCEE 0°C to +70°C 16 QSOP
MAX3098EBCSE 0°C to +70°C 16 SO
MAX3098EBCPE 0°C to +70°C 16 Plastic DIP
MAX3098EBEEE -40°C to +85°C 16 QSOP
MAX3098EBESE -40°C to +85°C 16 SO
MAX3098EBEPE -40°C to +85°C 16 Plastic DIP
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
______________________________________________________________________________________ 13
Package Information
SOICN.EPS
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
14 ______________________________________________________________________________________
Package Information (continued)
QSOP.EPS
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
______________________________________________________________________________________ 15
PDIPN.EPS
Package Information (continued)
MAX3097E/MAX3098E
±15kV ESD-Protected, 32Mbps, 3V/5V,
Triple RS-422/RS-485 Receivers with Fault Detection
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
NOTES