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19-1727; Rev 0; 7/00
15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection
General Description
The MAX3097E/MAX3098E feature three high-speed RS485/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 condition, 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 threshold values. The fault circuitry includes a capacitor-programmable delay to ensure that there are no erroneous fault conditions even at slow edge rates. Each receiver is capable of accepting data at rates up to 32Mbps.
Features
o Detects the Following RS-485 Faults: Open-Circuit Condition Short-Circuit Condition Low Differential Voltage Signal Common-Mode Range Violation o ESD Protection 15kV--Human Body Model 15kV--IEC 1000-4-2, Air-Gap Discharge Method 8kV--IEC 1000-4-2, Contact Discharge Method o Single +3V to +5.5V Operation o -10V to +13.2V Extended Common-Mode Range o Capacitor-Programmable Delay of Fault Indication Allows Error-Free Operation at Slow Data Rates o Independent and Universal Fault Outputs o 32Mbps Data Rate o 16-Pin QSOP is 40% Smaller than IndustryStandard 26LS31/32 Solutions
MAX3097E/MAX3098E
________________________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
Ordering Information
PART MAX3097ECEE MAX3097ECSE TEMP. RANGE 0C to +70C 0C to +70C PINPACKAGE 16 QSOP 16 SO
Typical Application Circuit
ENCODED SIGNALS A, A, B, B, Z, Z
Ordering Information continued at end of data sheet.
Pin Configuration
TOP VIEW
MAX3097E MAX3098E A1 ALARM OUTPUTS DSP 8 A2 MOTOR CONTROLLER B3 B4 Z5 MAX547 12-BIT D/A Z6 GND 7 DELAY 8 16 VCC 15 ALARMA 14 OUTA
RECEIVER OUTPUTS
MOTOR
MAX3097E MAX3098E
13 ALARMB 12 OUTB 11 ALARMZ 10 OUTZ 9 ALARMD
MOTOR DRIVER
QSOP/SO/DIP ________________________________________________________________ Maxim Integrated Products 1
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.
15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
ABSOLUTE MAXIMUM RATINGS
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 = +70C) 16-Pin QSOP (derate 8.3mW/C above +70C)............667mW 16-Pin SO (derate 8.7mW/C above +70C).................696mW 16-Pin Plastic DIP (derate 10.53mW/C above +70C).............................................................762mW Operating Temperature Ranges MAX3097EC_E...................................................0C to +70C MAX3098E_C_E .................................................0C to +70C MAX3097E_E_E ..............................................-40C to +85C MAX3098E_E_E ..............................................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VCC = +3V to +5.5V, TA = TMIN to TMAX , unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
PARAMETER Supply Voltage Range Supply Current Receiver Differential Threshold Voltage (Note 1) Receiver Input Hysteresis Output High Voltage Output Low Voltage Receiver Input Resistance Input Current (A , A , B , B (Z , Z ) Output Short-Circuit Current FAULT DETECTION MAX3097E Fault-Detection Receiver Differential Threshold Voltage (Note 3) MAX3098EA Fault-Detection Receiver Differential Threshold Voltage (Note 3) FDIFH VCM = 0 FDIFL FDIFH VCM = 0 FDIFL Low limit -0.20 -0.12 Low limit High limit -475 0.12 -275 0.20 V High limit 275 475 mV SYMBOL VCC ICC VTH VTH VOH VOL RIN No load -10V VCM 13.2V -10V VCM 13.2V VCC = 4.75V, IO = -4mA, VID = 200mV VCC = 3.0V, IO = -1mA, VID = 200mV VCC = 4.75V, IO = +4mA, VID = -200mV VCC = 3.0V, IO = +1mA, VID = -200mV -10V VCM 13.2V VIN = 13.2V (Note 2) VIN = -10V (Note 2) 90 0.07 -0.05 VCC - 1.5 VCC - 1.0 0.4 0.4 160 0.14 mA -0.11 105 mA -200 40 CONDITIONS MIN 3 TYP 3.1 MAX 5.5 4.0 +200 UNITS V mA mV mV V V k
IIN
VCC = 0 or 5.5V 0 VRO VCC
IOSR
2
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +5.5V, TA = TMIN to TMAX , unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
MAX3097E/MAX3098E
PARAMETER MAX3098EB Fault-Detection Receiver Differential Threshold Voltage (Note 3) Fault-Detection Common-Mode Voltage Range (Note 4) DELAY Current Source DELAY Threshold ESD PROTECTION
SYMBOL FDIFH VCM = 0 FDIFL FCMH FCML High limit Low limit
CONDITIONS High limit Low limit
MIN 70 -250 13.2
TYP
MAX 250
UNITS mV
-70 V A V
-10 9 1.55 3.1 10 1.73 3.29 15 15 8 11 1.90 3.5
VCC = 5V, VDELAY = 0 VCC = 3V VCC = 5V Human Body Model
ESD Protection (A, A, B, B, Z, Z)
IEC1000-4-2 (Air-Gap Discharge) IEC1000-4-2 (Contact Discharge)
kV
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 = +25C.)
PARAMETER Propagation Delay from Input to Output Receiver Skew |tPLH - tPHL| Channel-to-Channel Propagation Delay Skew Maximum Data Rate FAULT DETECTION Differential Fault Propagation Delay to Output (Note 5) Minimum Differential Slew Rate to Avoid False Alarm Output Common-Mode Fault Propagation Delay to Output (Note 5) tCMFLH CL = 15pF, Figures 1, 4 tCMFHL 1.5 tDFLH CLF = 15pF, Figures 1, 3 tDFHL MAX3097E (Note 6) MAX3098E (Note 7) 1.0 V/s 0.33 15 s 1.2 15 s fMAX SYMBOL tPLH, tPHL tSKEW CL = 15pF, Figures 1, 2 CONDITIONS VCC = 4.5V to 5.5V VCC = 3.0V to 3.6V MIN TYP MAX 75 85 10 10 32 UNITS ns ns ns Mbps
CL = 15pF, Figures 1, 2 CL = 15pF, Figures 1, 2 CL = 15pF, Figure 1
Note 1: Note 2: Note 3: Note 4:
VCM is the common-mode input voltage. VID is the differential input voltage. VIN is the input voltage at pins A, A, B, B, Z, Z. A differential terminating resistor is required for proper function of open-circuit fault detection (see Applications Information). 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. _______________________________________________________________________________________ 3
15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Typical Operating Characteristics
(Typical values are at VCC = +5V and TA = +25C.)
ALARMD OUTPUT DELAY vs. CAPACITANCE
MAX3097E/8Etoc01
RECEIVER PROPAGATION DELAY vs. TEMPERATURE
MAX3097E/8E toc02
SUPPLY CURRENT vs. TEMPERATURE
NO LOAD 4 SUPPLY CURRENT (mA) VCC = 5.0V 3 VCC = 3.3V 2
MAX3097E/8E toc03
10,000
70 RECEIVER PROPAGATION DELAY (ns)
5
ALARMD OUTPUT DELAY (s)
1000
60 VCC = 3.3V 50
100 VCC = 5V 10 VCC = 3V
VCC = 5.0V
40
1
1 1 10 100 CAPACITANCE (pF) 1000 10,000
30 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
RECEIVER OUTPUT LOW VOLTAGE vs. OUTPUT CURRENT
4.5 OUTPUT LOW VOLTAGE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -45 -40 -35 -30 -25 -20 -15 -10 -5 OUTPUT CURRENT (mA) 0 0 0 VCC = 3.3V VCC = 5.0V
MAX3097E/8E toc04
RECEIVER OUTPUT HIGH VOLTAGE vs. OUTPUT CURRENT
MAX3097E/8E toc05
DELAYED ALARM OUTPUT
MAX3097E/8E toc06
5.0
6 5 OUTPUT HIGH VOLTAGE (V) 4 3 2 1 VCC = 3.3V VCC = 5.0V
CH 1
GND
CH 2
GND
CH 3
GND
5
10
15
20
25
30
OUTPUT CURRENT (mA)
20s/div CH1: VA, 5V/div CH2: VALARMA, 5V/div CH3: VALARMD, 5V/div VA = GND, CDELAY = 270pF
4
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Typical Operating Characteristics (continued)
(Typical values are at VCC = +5V and TA = +25C.)
COMMON-MODE VOLTAGE FAULT (HIGH SIDE)
MAX3097E/8E toc07a
COMMON-MODE VOLTAGE FAULT (LOW SIDE)
MAX3097E/8E toc07b
MAX3097E LOW DIFFERENTIAL INPUT FAULT
MAX3097E/8E toc08
CH 1
GND
CH 1
GND
CH 1
GND
CH 2 CH 3 2ms/div CH1: VA + AC(60Hz), 10V/div CH2: VOUTA, 5V/div CH3: VALARMA, 5V/div VCC = 3V
GND GND
CH 2 CH 3 2ms/div CH1: VA + AC(60Hz), 10V/div CH2: VOUTA, 5V/div CH3: VALARMA, 5V/div VCC = 3V
GND GND
CH 2 100s/div CH1: VA, 200mV/div CH2: VALARMA, 5V/div VA = GND
GND
SLEW-RATE FAULT
MAX3097E/8E toc09
FAULT-DETECTION RECEIVER DIFFERENTIAL THRESHOLD VOLTAGE SHIFT vs. COMMON-MODE VOLTAGE
12 THRESHOLD SHIFT (mV) GND 8 4 0 -4 -8 MAX3097E
MAX3097E/8E toc10
CH 1
MAX3098E
CH 2
GND
CH1: VA, 5V/div CH2: VALARMA, 5V/div SLEW RATE = 0.05V/s VA = GND
-10
-5
0
5
10
COMMON-MODE VOLTAGE (V)
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME A A B B Z Z GND DELAY Noninverting Receiver A Input Inverting Receiver A Input Noninverting Receiver B Input Inverting Receiver B Input Noninverting Receiver Z Input Inverting Receiver Z Input Ground 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. 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. 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. 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. 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. 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. 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. 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. Power Supply FUNCTION
9
ALARMD
10
OUTZ
11
ALARMZ
12
OUTB
13
ALARMB
14
OUTA
15 16
ALARMA VCC
6
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection
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 circuitry 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 motorshaft encoders with standard A, B, and Z outputs (see Using the MAX3097E/MAX3098E as Shaft Encoder Receivers). The devices provide an alarm for open-circuit 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
Test Circuits and Waveforms
CLF ALARMA OR (FAULT OUTPUT) ALARMD
A VA VID A VA
+3V VID -3V OV tPLH VOH RO VOL VCC/2 OV
RISE/FALL TIMES 2ns
OUTA CL
tPHL VCC/2
Figure 1. Typical Receiver Test Circuit
Figure 2. Propagation Delay
+3.0V FDIFH VID -3.0V VOH ALARM OR ALARMD VOL tDFLH VCC/2 tDFHL VCC/2 OV FDIFL
FCMH VIN OV FCML
tCMFLH VOH ALARM OR ALARMD VOL
tCMFHL tCMFLH VCC/2 VCC/2 VCC/2
tCMFHL VCC/2
Figure 3. Fault-Detection Timing
Figure 4. Common-Mode Fault Propagation Delay
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Table 1. MAX3097E Alarm Function Table (Each Receiver)
INPUTS VID (DIFFERENTIAL INPUT VOLTAGE) 0.475V <0.475V and 0.275V <0.275V and 0.2V 0.2V and -0.2V -0.2V and >-0.275V -0.275V and >-0.475V -0.475V X <-10V or >+13.2V 13.2V and -10V COMMON-MODE VOLTAGE OUT_ 1 1 1 Indeterminate (Note 2) 0 0 0 Indeterminate (Note 3) OUTPUTS ALARM_ 0 Indeterminate 1 1 1 Indeterminate 0 1 ALARMD t DELAY (NOTE 1) 0 Indeterminate 1 1 1 Indeterminate 0 1 Outside Common-Mode Voltage Range FAULT CONDITION
Normal Operation Indeterminate Low Input Differential Voltage Low Input Differential Voltage Low Input Differential Voltage Indeterminate
X = Don't care 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.
Table 2. MAX3098EA Alarm Function Table (Each Receiver)
INPUTS VID (DIFFERENTIAL INPUT VOLTAGE) 0.2V <0.2V and 0.12V <0.12V and -0.12V -0.12V and -0.2V -0.2V X <-10V or >+13.2V 13.2V and 10V COMMON-MODE VOLTAGE OUT_ 1 Indeterminate Indeterminate (Note 2) Indeterminate 0 Indeterminate (Note 3) OUTPUTS ALARM_ 0 Indeterminate 1 Indeterminate 0 1 ALARMD t DELAY (NOTE 1) 0 Indeterminate 1 Indeterminate 0 1 FAULT CONDITION
Normal Operation Indeterminate Low Input Differential Voltage Indeterminate Normal Operation Outside Common-Mode Voltage Range
X = Don't care; for B-grade functionality, replace VID input values in Table 2 with B-grade parameters from Electrical Characteristics. 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.
8
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
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 protection against static electricity found in normal operation. 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 discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the device through a 1.5k resistor. 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 integrated circuits. The MAX3097E/MAX3098E help you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without additional ESD-protection components. 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 generally 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 storage 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.
RC 1M CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1.5k DISCHARGE RESISTANCE DEVICE UNDER TEST
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
Cs 100pF
STORAGE CAPACITOR
tDL CURRENT WAVEFORM
Figure 5a. Human Body ESD Test Model
Figure 5b. Human Body Model Current Waveform
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
___________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) techniques are used to count the pulses and provide feedback 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).
HIGHVOLTAGE DC SOURCE RC 50M to 100M CHARGE-CURRENT LIMIT RESISTOR RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 150pF
STORAGE CAPACITOR
Figure 6a. IEC 1000-4-2 ESD Test Model
I 100% 90% IPEAK
Detecting Faults
Signal integrity from the shaft encoder to the DSP is essential for reliable system operation. Degraded signals could cause problems ranging from simple miscounts 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 signal, open-circuit wires, short-circuit wires, and an input signal outside the common-mode input voltage range of the receiver.
10% tr = 0.7ns to 1ns 30ns 60ns t
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
Detecting Short Circuits
In Figure 8, if wires A and A are shorted together, then A and A will 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 A is less than the differential fault threshold.
A A B
Detecting Open-Circuit Conditions
Detecting an open-circuit condition is similar to detecting a short-circuit condition and relies on the terminating resistor being across A and A. For example, if the wire drops out of the A terminal, A pulls A through the terminating resistor to look like the same signal. In this condition, VID is approximately 0 and a fault occurs.
B Z
Z
Figure 7. Typical Shaft Encoder Output
10
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Common-Mode Range
The MAX3097E/MAX3098E contain circuitry that detects if the input stage is going outside its useful common-mode range. If the received data could be unreliable, a fault signal is triggered. 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.
Detecting Low Input Differential
Due to cable attenuation on long wire runs, it is possible that V ID < 200mV, and incorrect data will be received. In this condition, a fault will be indicated.
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 tD is in s and CDELAY is in pF.
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 Nchannel MOSFET so that in normal operation with no faults, the current source (10A typ) is shunted to
A A ALARMA ALARMB ALARMZ
DELAY CURRENT SOURCE NORMAL OPERATION SHORT CIRCUIT A TO A NMOS CDELAY* (EXTERNAL) G1 tDLY
DELAY COMPARATOR ALARMD
Figure 8. Short-Circuit Detection
ALARMA
ALARM_ DELAY
DELAY THRESHOLD
ALARMB tD ALARMD tD
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
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Ordering Information (continued)
PART MAX3097ECPE MAX3097EEEE MAX3097EESE MAX3097EEPE MAX3098EACEE MAX3098EACSE MAX3098EACPE MAX3098EAEEE MAX3098EAESE MAX3098EAEPE MAX3098EBCEE MAX3098EBCSE MAX3098EBCPE MAX3098EBEEE MAX3098EBESE MAX3098EBEPE TEMP. RANGE 0C to +70C -40C to +85C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +85C PINPACKAGE 16 Plastic DIP 16 QSOP 16 SO 16 Plastic DIP 16 QSOP 16 SO 16 Plastic DIP 16 QSOP 16 SO 16 Plastic DIP 16 QSOP 16 SO 16 Plastic DIP 16 QSOP 16 SO 16 Plastic DIP
Z ALARMD B OUTB B ALARMZ Z OUTZ A OUTA A ALARMB
Functional Diagram
VCC ALARMA
MAX3097E MAX3098E
GND
DELAY
Chip Information
TRANSISTOR COUNT: 675 PROCESS: CMOS
12
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection
Package Information
SOICN.EPS
MAX3097E/MAX3098E
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13
15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
Package Information (continued)
QSOP.EPS
14
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15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection
Package Information (continued)
PDIPN.EPS
MAX3097E/MAX3098E
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15
15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E
NOTES
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 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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Price & Availability of MAX3097

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