19-1727; Rev 0; 7/00 ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection Features ♦ Detects the Following RS-485 Faults: Open-Circuit Condition Short-Circuit Condition Low Differential Voltage Signal Common-Mode Range Violation 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. ♦ Single +3V to +5.5V Operation ________________________Applications ♦ Independent and Universal Fault Outputs RS-485/RS-422 Receivers for Motor-Shaft Encoders High-Speed, Triple RS-485/RS-422 Receiver with Extended Electrostatic Discharge (ESD) ♦ ESD Protection ±15kV—Human Body Model ±15kV—IEC 1000-4-2, Air-Gap Discharge Method ±8kV—IEC 1000-4-2, Contact Discharge Method ♦ -10V to +13.2V Extended Common-Mode Range ♦ Capacitor-Programmable Delay of Fault Indication Allows Error-Free Operation at Slow Data Rates ♦ 32Mbps Data Rate ♦ 16-Pin QSOP is 40% Smaller than IndustryStandard 26LS31/32 Solutions Ordering Information Triple RS-485/RS-422 Receiver with Input Fault Indication PART Telecommunications PINPACKAGE TEMP. RANGE Embedded Systems Typical Application Circuit MAX3097ECEE 0°C to +70°C 16 QSOP MAX3097ECSE 0°C to +70°C 16 SO Ordering Information continued at end of data sheet. ENCODED SIGNALS Pin Configuration A, A, B, B, Z, Z TOP VIEW MAX3097E MAX3098E RECEIVER OUTPUTS ALARM OUTPUTS DSP 8 MOTOR MOTOR CONTROLLER A 1 16 VCC A 2 15 ALARMA B 3 14 OUTA B 4 Z 5 MAX547 12-BIT D/A MAX3097E MAX3098E Z 6 13 ALARMB 12 OUTB 11 ALARMZ GND 7 10 OUTZ DELAY 8 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. MAX3097E/MAX3098E 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. MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 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 = +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 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 = +25°C.) PARAMETER Supply Voltage Range Supply Current Receiver Differential Threshold Voltage (Note 1) Receiver Input Hysteresis SYMBOL VCC ICC No load VTH -10V ≤ VCM ≤ 13.2V ∆VTH -10V ≤ VCM ≤ 13.2V Output High Voltage VOH Output Low Voltage VOL Receiver Input Resistance RIN Input Current (A , A , B , B (Z , Z ) Output Short-Circuit Current CONDITIONS IIN IOSR MIN 3 TYP MAX 5.5 UNITS V 3.1 4.0 mA +200 mV -200 40 VCC = 4.75V, IO = -4mA, VID = 200mV VCC - 1.5 VCC = 3.0V, IO = -1mA, VID = 200mV VCC - 1.0 mV V VCC = 4.75V, IO = +4mA, VID = -200mV 0.4 VCC = 3.0V, IO = +1mA, VID = -200mV 0.4 -10V ≤ VCM ≤ 13.2V VCC = 0 or 5.5V 90 160 VIN = 13.2V (Note 2) 0.07 0.14 VIN = -10V (Note 2) -0.05 -0.11 V kΩ mA 0 ≤ VRO ≤ VCC ±105 mA FAULT DETECTION 2 MAX3097E Fault-Detection Receiver Differential Threshold Voltage (Note 3) FDIFH MAX3098EA Fault-Detection Receiver Differential Threshold Voltage (Note 3) FDIFH High limit 275 475 Low limit -475 -275 High limit 0.12 0.20 Low limit -0.20 -0.12 VCM = 0 FDIFL mV VCM = 0 FDIFL V _______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection (VCC = +3V to +5.5V, TA = TMIN to TMAX , unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MAX3098EB Fault-Detection Receiver Differential Threshold Voltage (Note 3) FDIFH Fault-Detection Common-Mode Voltage Range (Note 4) FCMH High limit FCML Low limit MIN TYP MAX High limit 70 250 Low limit -250 -70 VCM = 0 mV FDIFL DELAY Current Source 13.2 -10 VCC = 5V, VDELAY = 0 DELAY Threshold UNITS 9 10 11 VCC = 3V 1.55 1.73 1.90 VCC = 5V 3.1 3.29 3.5 V µA V ESD PROTECTION ESD Protection (A, A, B, B, Z, Z) Human Body Model ±15 IEC1000-4-2 (Air-Gap Discharge) ±15 IEC1000-4-2 (Contact Discharge) ±8 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 = +25°C.) PARAMETER Propagation Delay from Input to Output Receiver Skew |tPLH - tPHL| SYMBOL tPLH, tPHL tSKEW Channel-to-Channel Propagation Delay Skew Maximum Data Rate fMAX CONDITIONS CL = 15pF, Figures 1, 2 MIN TYP MAX VCC = 4.5V to 5.5V 75 VCC = 3.0V to 3.6V 85 UNITS ns CL = 15pF, Figures 1, 2 ±10 ns CL = 15pF, Figures 1, 2 ±10 ns CL = 15pF, Figure 1 32 Mbps FAULT DETECTION Differential Fault Propagation Delay to Output (Note 5) tDFLH µs 1.2 tDFHL Minimum Differential Slew Rate to Avoid False Alarm Output Common-Mode Fault Propagation Delay to Output (Note 5) 15 CLF = 15pF, Figures 1, 3 MAX3097E (Note 6) 1.0 MAX3098E (Note 7) 0.33 V/µs tCMFLH 15 CL = 15pF, Figures 1, 4 tCMFHL µs 1.5 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. Note 1: Note 2: Note 3: Note 4: _______________________________________________________________________________________ 3 MAX3097E/MAX3098E ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (Typical values are at VCC = +5V and TA = +25°C.) VCC = 5V VCC = 3V 1 10 100 1000 50 VCC = 5.0V 40 10,000 4 VCC = 5.0V 3 VCC = 3.3V 2 1 0 -40 -20 0 20 40 60 -40 80 -20 0 20 40 60 TEMPERATURE (°C) RECEIVER OUTPUT LOW VOLTAGE vs. OUTPUT CURRENT RECEIVER OUTPUT HIGH VOLTAGE vs. OUTPUT CURRENT DELAYED ALARM OUTPUT 3.5 3.0 VCC = 3.3V 2.0 1.5 1.0 MAX3097E/8E toc05 VCC = 5.0V 5 OUTPUT HIGH VOLTAGE (V) MAX3097E/8E toc04 VCC = 5.0V 6 CH 1 VCC = 3.3V 3 CH 2 GND CH 3 GND 2 1 0 -45 -40 -35 -30 -25 -20 -15 -10 -5 OUTPUT CURRENT (mA) 0 GND 4 0.5 0 80 MAX3097E/8E toc06 TEMPERATURE (°C) 4.5 4 NO LOAD CAPACITANCE (pF) 5.0 2.5 VCC = 3.3V 30 1 4.0 60 5 SUPPLY CURRENT (mA) 100 MAX3097E/8E toc02 1000 70 RECEIVER PROPAGATION DELAY (ns) MAX3097E/8Etoc01 ALARMD OUTPUT DELAY (µs) 10,000 10 SUPPLY CURRENT vs. TEMPERATURE RECEIVER PROPAGATION DELAY vs. TEMPERATURE MAX3097E/8E toc03 ALARMD OUTPUT DELAY vs. CAPACITANCE OUTPUT LOW VOLTAGE (V) MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 0 5 10 15 20 OUTPUT CURRENT (mA) 25 30 20µs/div CH1: VA, 5V/div CH2: VALARMA, 5V/div CH3: VALARMD, 5V/div VA = GND, CDELAY = 270pF _______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection COMMON-MODE VOLTAGE FAULT (HIGH SIDE) GND CH 1 CH 2 GND CH 2 GND CH 3 MAX3097E/8E toc08 MAX3097E/8E toc07b MAX3097E/8E toc07a CH 1 GND CH 1 GND GND CH 2 GND GND 2ms/div CH1: VA + AC(60Hz), 10V/div CH2: VOUTA, 5V/div CH3: VALARMA, 5V/div VCC = 3V 2ms/div CH1: VA + AC(60Hz), 10V/div CH2: VOUTA, 5V/div CH3: VALARMA, 5V/div VCC = 3V FAULT-DETECTION RECEIVER DIFFERENTIAL THRESHOLD VOLTAGE SHIFT vs. COMMON-MODE VOLTAGE CH 2 12 GND THRESHOLD SHIFT (mV) MAX3097E/8E toc09 SLEW-RATE FAULT CH 1 100µs/div CH1: VA, 200mV/div CH2: VALARMA, 5V/div VA = GND MAX3097E/8E toc10 CH 3 MAX3097E LOW DIFFERENTIAL INPUT FAULT COMMON-MODE VOLTAGE FAULT (LOW SIDE) 8 MAX3097E 4 0 MAX3098E GND -4 -8 CH1: VA, 5V/div CH2: VALARMA, 5V/div SLEW RATE = 0.05V/µs VA = GND -10 -5 0 5 10 COMMON-MODE VOLTAGE (V) _______________________________________________________________________________________ 5 MAX3097E/MAX3098E Typical Operating Characteristics (continued) (Typical values are at VCC = +5V and TA = +25°C.) ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection MAX3097E/MAX3098E Pin Description 6 PIN NAME 1 A Noninverting Receiver A Input FUNCTION 2 A Inverting Receiver A Input 3 B Noninverting Receiver B Input 4 B Inverting Receiver B Input 5 Z Noninverting Receiver Z Input 6 Z Inverting Receiver Z Input 7 GND 8 DELAY 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. 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 _______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 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. Test Circuits and Waveforms CLF A ALARMA OR (FAULT OUTPUT) ALARMD +3V VID VA RISE/FALL TIMES ≤2ns OV OV tPLH tPHL -3V OUTA VID VOH CL A VCC/2 RO VA VCC/2 VOL Figure 1. Typical Receiver Test Circuit Figure 2. Propagation Delay +3.0V FCMH VIN OV FDIFH OV VID FCML FDIFL -3.0V VOH ALARM OR ALARMD VOL tDFHL tDFLH VCC/2 Figure 3. Fault-Detection Timing VCC/2 tCMFLH VOH ALARM OR ALARMD VOL tCMFHL tCMFLH VCC/2 VCC/2 tCMFHL VCC/2 VCC/2 Figure 4. Common-Mode Fault Propagation Delay _______________________________________________________________________________________ 7 MAX3097E/MAX3098E Detailed Description MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection Table 1. MAX3097E Alarm Function Table (Each Receiver) INPUTS VID (DIFFERENTIAL INPUT VOLTAGE) OUTPUTS 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 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 0 0 0 Indeterminate (Note 3) 1 1 ≤0.2V and ≥-0.2V X ≤13.2V and ≥-10V <-10V or >+13.2V Indeterminate Outside Common-Mode Voltage Range 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) OUTPUTS 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 Indeterminate (Note 2) 1 1 Low Input Differential Voltage ≤-0.12V and ≥ -0.2V Indeterminate Indeterminate Indeterminate Indeterminate ≤-0.2V 0 0 0 Normal Operation Indeterminate (Note 3) 1 1 Outside Common-Mode Voltage Range <0.12V and ≥ -0.12V X ≤13.2V and ≥10V <-10V or >+13.2V 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 _______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 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 1.5kΩ resistor. RD 1.5k RC 1MΩ CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE Cs 100pF 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. IP 100% 90% DISCHARGE RESISTANCE STORAGE CAPACITOR 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. Ir AMPERES DEVICE UNDER TEST 36.8% 10% 0 0 Figure 5a. Human Body ESD Test Model PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE) tRL TIME tDL CURRENT WAVEFORM Figure 5b. Human Body Model Current Waveform _______________________________________________________________________________________ 9 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. ___________Applications Information RC 50MΩ to 100MΩ 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. CHARGE-CURRENT LIMIT RESISTOR HIGHVOLTAGE DC SOURCE Detecting Faults 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. 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. 10 DISCHARGE RESISTANCE STORAGE CAPACITOR DEVICE UNDER TEST Figure 6a. IEC 1000-4-2 ESD Test Model I 100% 90% 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). 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. Cs 150pF RD 330Ω IPEAK MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 10% tr = 0.7ns to 1ns t 30ns 60ns Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform A A B B Z Z Figure 7. Typical Shaft Encoder Output ______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 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. 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 (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 tD is in µs and CDELAY is in pF. DELAY CURRENT SOURCE A A NORMAL OPERATION SHORT CIRCUIT A TO A ALARMA ALARMB ALARMZ NMOS DELAY COMPARATOR ALARMD CDELAY* (EXTERNAL) Figure 8. Short-Circuit Detection G1 tDLY ALARMA ALARM_ DELAY THRESHOLD DELAY ALARMB ALARMD tD tD *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. ALARMD Figure 9. Delayed Alarm Output Figure 10. ALARMD Simplified Schematic ______________________________________________________________________________________ 11 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. MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection Ordering Information (continued) PART TEMP. RANGE Functional Diagram PINPACKAGE VCC MAX3097ECPE 0°C to +70°C 16 Plastic DIP MAX3097EEEE -40°C to +85°C 16 QSOP A MAX3097EESE -40°C to +85°C 16 SO A 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 ALARMA OUTA ALARMB B OUTB B ALARMZ Z OUTZ Z ALARMD MAX3097E MAX3098E DELAY GND Chip Information TRANSISTOR COUNT: 675 PROCESS: CMOS 12 ______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection SOICN.EPS ______________________________________________________________________________________ 13 MAX3097E/MAX3098E Package Information ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection QSOP.EPS MAX3097E/MAX3098E Package Information (continued) 14 ______________________________________________________________________________________ ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection PDIPN.EPS ______________________________________________________________________________________ 15 MAX3097E/MAX3098E Package Information (continued) MAX3097E/MAX3098E ±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection 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 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.