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19-3843; Rev 1; 6/07
Space-Saving, 8-Channel Relay/Load Driver
General Description
The MAX4896 8-channel relay and load driver is designed for medium voltage applications up to 50V. This device is offered in a 20-pin, 5mm x 5mm TQFN package, resulting in substantial board space savings. The MAX4896 8-channel relay driver offers built-in inductive kickback protection, drive for latching/ nonlatching or dual-coil relays, and open-load and short-circuit fault detection.The MAX4896 also protects against overcurrent conditions. Each independent open-drain output features a 3 (typ) on-resistance, and is guaranteed to sink 200mA of load current (VS 4.5V). A built-in overvoltage protection clamp handles kickback-voltage transients, which are common when driving inductive loads. Thermal-shutdown circuitry shuts off all outputs (OUT_) when the junction temperature exceeds +160C. The MAX4896 employs a reset input that allows the user to turn off all outputs simultaneously with a single control line. The MAX4896 includes a 10MHz SPITM-/QSPITM-/ MICROWIRETM-compatible serial interface. The serial interface is compatible with TTL-/CMOS-logic voltage levels and operates with a single +2.7V to +5.5V supply. In addition, the SPI output data can be used for diagnostics purposes including open-load and shortcircuit fault detection. The MAX4896 is offered in the extended (-40C to +85C) and automotive (-40C to +125C) operating temperature ranges.
Features
Supports Up to 50V Continuous Drain-to-Source Voltage Guaranteed Drive Current: VS 4.5V 200mA (All Channels On) 410mA (Individual Channels) VS 3.6V 100mA Built-In Output Clamp Protects Against Inductive Kickback +2.7V to +5.5V Logic Supply Voltage RESET Input Turns Off All Outputs Simultaneously Built-in Power-On Reset Automotive Temperature Range (-40C to +125C) SPI-/QSPI-/MICROWIRE-Compatible Serial Interface Serial Digital Output for Daisy Chaining and Diagnostics FLAG Output for P Interrupt Open-Load and Short-Circuit Detection and Protection Thermal Shutdown Low 100A (max) Quiescent Supply Current Space-Saving, 5mm x 5mm, 20-Pin TQFN Package
MAX4896
Typical Operating Circuit
Vcc = 2.7V TO 5.5V VRELAY 0.1F
Applications
Industrial Equipment White Goods Power-Grid Monitoring and Protection Equipment Automotive Relay Control ATE
PDCD INT FLAG RESET C SCLK CS DIN DOUT
VS OUT1
RELAY COIL 1
Ordering Information
PART MAX4896ETP+ TEMP RANGE -40C to +85C -40C to +125C PINPACKAGE 20 TQFN-EP* (5mm x 5mm) 20 TQFN-EP* (5mm x 5mm) PACKAGE CODE T2055-5 T2055-5
VRELAY
MAX4896
RELAY COIL 8 OUT8 GND PGND
MAX4896ATP+
SLPD
*EP = Exposed paddle + Denotes a lead-free package. SPI and QSPI are trademarks of Motorola, Inc.
Pin Configuration appears at end of data sheet.
MICROWIRE is a trademark of National Semiconductor Corp. 1
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Space-Saving, 8-Channel Relay/Load Driver MAX4896
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.) VS ......................................................................... -0.3V to +7.0V OUT_ ....................................................................(-0.3V to +50V) Continuous OUT_ Voltage ...................................................+50V CS, SCLK, DIN, RESET, SPLD, PDCD ..................-0.3V to +7.0V DOUT ............................................................-0.3V to (VS + 0.3V) PGND to GND............................................(-0.3V to +0.3V) Continuous OUT_ Current, TA = +25C (Note 1) All Outputs On..................................................................210mA Single Output On .............................................................420mA Continuous Power Dissipation (TA = +70C) 20-Pin TQFN (derate 21.3mW/C above +70C) ......1702mW JA ................................................................................+47C/W Maximum Output Clamp Energy (EOUT_) ...........................30mJ Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +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.
Note 1: Maximum continuous current at a given temperature must be calculated such that the maximum continuous power dissipation for the package is not exceeded.
ELECTRICAL CHARACTERISTICS
(VS = +2.7V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER Operating Voltage Quiescent Current Dynamic Average Supply Current Thermal Shutdown Thermal-Shutdown Hysteresis Power-On Reset Power-On-Reset Hysteresis SYMBOL VS ICC IS TSHD TSHDH VRST VRSTH VS = 2.7V to 3.6V VS = 4.5V to 5.5V VS = 2.7V to 3.6V VS = 4.5V to 5.5V 230 Input voltages = 0 or +5.5V -1 10 TJ = +25C TJ = +125C TJ = +150C TJ = +25C TJ = +125C 3 5 6 11 12 4 7 8 -1 +1 A +1 2.0 2.4 0.6 0.8 V mV A pF VS falling 1.8 IOUT_ = 0, logic inputs = VS = 3.6V 0 or VS, RESET = low VS = 5V fSCLK = 10MHz, fDIN = 0.5 x fCLK, COUT = 50pF, VS = 5.5V +160 20 2.05 140 2.3 CONDITIONS MIN 2.7 5 10 TYP MAX 5.5 70 100 6 UNITS V A mA C C V mV
DIGITAL INPUTS (SCLK, DIN, CS, RESET, PDCD, SPLD) Input Logic-High Voltage Input Logic-Low Voltage Input Logic Hysteresis Input Leakage Currents Input Capacitance VIH VIL VHYST ILEAK CIN V
RELAY OUTPUT DRIVERS (OUT1-OUT8) IOUT = 50mA, VS = 2.7V OUT_ ON Resistance RON IOUT = 100mA, VS = 4.5V IOUT Off-Leakage Current ILEAK
TJ = +150C PDCD = high or RESET = low, all outputs off
2
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Space-Saving, 8-Channel Relay/Load Driver
ELECTRICAL CHARACTERISTICS (continued)
(VS = +2.7V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER OUT Clamping Voltage OUT Current-Limit Threshold OUT Capacitance DIAGNOSTIC Open-Load Detection Voltage Threshold Open-Load Detection-VoltageThreshold Hysteresis OUT_ Pulldown Current Fault Delay/Filtering Time VDS(OL) VDS(OLH)
IPD(OL)
MAX4896
SYMBOL VCLAMP ILIM (Note 3) VS 4.5V
CONDITIONS
MIN 50 400
TYP
MAX 75 960
UNITS V mA pF
VOUT = 16V, f = 1MHz
30
OUT_ falling
0.75
1 40
1.15
V mV
PDCD = low From rising edge at CS at 50% to valid diagnostic data 2.7V VS 3.6V, ISINK = 0.3mA 4.5V VS 5.5V, ISINK = 0.5mA 2.7V VS 3.6V, ISOURCE = 0.25mA 4.5V VS 5.5V, ISOURCE = 0.4mA ISINK = 0.5mA 4.5V VS 5.5V, VFLAG = 5.5V From rising edge of CS at 50% to VOUT_ = 90%VP, VP = 15V, RL = 300, CL = 50pF, 2.7V VS < 3.6V From rising edge of CS at 50% to VOUT_ = 90%VP, VP =16V, RL = 150, CL = 50pF, 4.5V VS 5.5V From rising edge of CS at 50% to VOUT_ = 10%VP, VP = 15V, RL = 300, CL = 50pF, 2.7V VS < 3.6V From rising edge of CS at 50% to VOUT_ = 90%VP, VP = 16V, RL = 150, CL = 50pF, 4.5V < VS 5.5V
150 30
300 90
500 280
A s
tD(FAULT)
DIGITAL OUTPUT (DOUT, FLAG) DOUT Low Voltage DOUT High Voltage FLAG Low Voltage FLAG Off-Leakage Current TIMING 20 s 10 VOL VOH 0.4 0.4 VS - 0.5 VS - 0.5 0.4 -1 +1 V V V A
Turn-On Time (OUT_)
tON
15 s 10
Turn-Off Time (OUT_)
tOFF
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3
Space-Saving, 8-Channel Relay/Load Driver MAX4896
ELECTRICAL CHARACTERISTICS (continued)
(VS = +2.7V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER SYMBOL TA = +85C SCLK Frequency fSCLK TA = +125C Cycle Time CS Fall-to-SCLK Rise Setup CS Rise-to-SCLK Hold SCLK High Time SCLK Low Time Data Setup Time Data Hold Time tCH + tCL tCSS tCSH tCH tCL tDS tDH 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 50% of SCLK to 20% of VS falling edge, CL = 50pF, 50% at SCLK to 80% of VS rising edge 20% of VS to 70% of VS, CL = 50pF (Note 4) 20% of VS to 70% of VS, CL = 50pF (Note 4) 2.7V VS 3.6V CONDITIONS 2.7V VS < 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 200 100 100 50 100 50 80 40 80 40 40 20 5 0 70 ns 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 2.7V VS 3.6V 4.5V VS 5.5V 70 30 2 s 2 2 s 2 ns 0 MIN 0 TYP MAX 6 11 5 10 ns ns ns ns ns ns ns MHz UNITS
SCLK Fall-to-DOUT Valid
tDO
Rise Time (DIN, SCLK, CS, RESET) Fall Time (DIN, SCLK, CS, RESET) RESET Min Pulse Width
tSCR
tSCF tRW
Note 2: Specifications at -40C are guaranteed by design and not production tested. Note 3: The output stages are compliant with the transient immunity requirements, as specified in ISO 7637 Part 3 with test pulses 1, 2, 3a, and 3b. Note 4: Guaranteed by design.
4
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Space-Saving, 8-Channel Relay/Load Driver MAX4896
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
QUIESCENT CURRENT vs. SUPPLY VOLTAGE
12 11 10 9 8 7 6 5 4 3 2 1 0 2.7
MAX4896 toc01
SUPPLY CURRENT vs. fCLK
5.5 SUPPLY CURRENT (mA) 5.0 RON () 4.5 4.0 3.5 3.0 VS = 5V VS = 3.3V fDIN = 0.5 x fCLK
MAX4896 toc02
ON-RESISTANCE vs. SUPPLY VOLTAGE
6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 VS = 2.7V 2.5 2.0 10 2.7 IOUT_SINK = 50mA 3.1 3.5 3.9 4.3 4.7 5.1 5.5 IOUT_SINK = 100mA
MAX4896 toc 03
ALL LOGIC INPUTS = VS
6.0
7.0
QUIESCENT CURRENT (A)
TA = +125C
TA = +85C
TA = +25C TA = -40C 3.1 3.5 3.9 4.3 4.7 5.1 5.5
2.5 2.0 0.1 1 fCLK (MHz)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
ON-RESISTANCE vs. TEMPERATURE
MAX4896 toc04
ON-RESISTANCE vs. TEMPERATURE
IOUT_SINK = 100mA 7 6 RON () 5 4 3 VS = 5.5V VS = 3.3V VS = 5V VS = 2.7V
MAX4896 toc05
POWER-ON RESET VOLTAGE vs. TEMPERATURE
MAX4896 DS toc06
8 IOUT_SINK = 50mA 7 6 RON () 5 4 VS = 5V 3 2 1 VS = 5.5V VS = 3.3V VS = 2.7V
8
2.14 POWER-ON-RESET VOLTAGE (V) 2.12 2.10 2.08 2.06 2.04 2.02 2.00
2 1
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
OUTPUT OFF LEAKAGE CURRENT vs. SUPPLY VOLTAGE
MAX4896 toc07
OUT LEAKAGE CURRENT vs. TEMPERATURE
PDCD = VS OUT LEAKAGE CURRENT (nA) 10
MAX4896 DS toc08
INPUT LOGIC THRESHOLD vs. SUPPLY VOLTAGE
2.25 INPUT LOGIC THRESHOLD (V) 2.00 1.75 1.50 1.25 1.00 0.75
MAX4896 toc09
100 90 OUTPUT OFF LEAKAGE (pA) 80 70 60 50 40 30 20 10 0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VOUT = 50V VOUT = 24V
100
2.50
1
VOUT = 50V VOUT = 24V VOUT = 12V
0.1
VOUT = 12V
0.01
0.001 5.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) SUPPLY VOLTAGE (V)
0.50 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 SUPPLY VOLTAGE (V)
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5
Space-Saving, 8-Channel Relay/Load Driver MAX4896
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
OUT_ CURRENT LIMIT vs. SUPPLY VOLATGE
MAX4896 toc11
TURN-ON/TURN-OFF DELAY TIME vs. SUPPLY VOLTAGE
MAX4896 toc10
TURN-ON/TURN-OFF DELAY TIME vs. SUPPLY VOLTAGE
5.0 4.5 tON/tOFF DELAY TIME (s) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 tON 4.5 4.7 4.9 5.1 5.3 5.5 tOFF VOUT = 50V RL = 150 CL = 50pF 800 750 OUTPUT CURRENT LIMIT (mA) 700 650
VOUT = 15V 2.5 tON/tOFF DELAY TIME (s) 2.0 1.5 1.0
RL = 300 CL = 50pF
TA = -40C TA = +25C
tOFF
TA = +85C 600 550 500 450 400 4.5 4.7 4.9 5.1 5.3 5.5 TA = +125C
tON 0.5 0 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 SUPPLY VOLTAGE (V)
0 SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
OUT CLAMP VOLTAGE vs. TEMPERATURE
MAX4896 toc13
BACK-EMF CLAMPING WITH STANDARD +12V RELAY
MAX4896 toc14
BACK-EMF CLAMPING WITH STANDARD +24V RELAY
MAX4896 toc15
66.0 65.8 0UT CLAMP VOLTAGE (V) 65.6 65.4 65.2 65.0 64.8 64.6 64.4 64.2 64.0
VS = 3.3V RESET (2V/div)
VS = 5V RESET 5V/div
MAX4896 toc12
3.0
OUT (20V/div) -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 1ms/div 1ms/div
OUT (20V/div)
6
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Space-Saving, 8-Channel Relay/Load Driver
Pin Description
PIN 1 2 3 4 5 6 NAME RESET CS DIN SCLK DOUT PDCD FUNCTION Reset Input. Drive RESET low to clear all latches and registers (all outputs are turned off). All OUT pulldown currents are disabled when RESET = low. Chip Select Input. Drive CS low to select the device. When CS is low, data at DIN is clocked into the 8-bit shift register on SCLK's rising edge. Drive CS from low to high to latch the data to the registers. Serial Data Input Serial Clock Input Serial Data Output. DOUT is the output of the 8-bit shift register. This output can be used to daisy chain multiple MAX4896s. The data at DOUT appears synchronous to SCLK's falling edge. Pulldown Current Disable. Drive PDCD high to disable OUT's pulldown current source. Drive PDCD low to enable OUT_ pulldown current source. PDCD must be low to detect an open-load fault. Short-Protection Latch-Off Disable Input. Drive SPLD high to disable the built-in short-circuit protection latch-off feature. When SPLD is low, an overloaded channel is turned off immediately. See the Output Short-Circuit/Current-Limiting Protection section. Open-Drain Output 8. Connect OUT8 to the low side of a relay coil. OUT8 is pulled to PGND when activated and is otherwise high impedance. Open-Drain Output 7. Connect OUT7 to the low side of a relay coil. OUT7 is pulled to PGND when activated and is otherwise high impedance. Power Ground. PGND is the ground return path for the output sinks. Connect PGND pins together and to GND. Open-Drain Output 6. Connect OUT6 to the low side of a relay coil. OUT6 is pulled to PGND when activated and is otherwise high impedance. Open-Drain Output 5. Connect OUT5 to the low side of a relay coil. OUT5 is pulled to PGND when activated and is otherwise high impedance. Ground Open-Drain Output 4. Connect OUT4 to the low side of a relay coil. OUT4 is pulled to PGND when activated and is otherwise high impedance. Open-Drain Output 3. Connect OUT3 to the low side of a relay coil. OUT3 is pulled to PGND when activated and is otherwise high impedance. Open-Drain Output 2. Connect OUT2 to the low side of a relay coil. OUT2 is pulled to PGND when activated and is otherwise high impedance. Open-Drain Output 1. Connect OUT1 to the low side of a relay coil. OUT1 is pulled to PGND when activated and is otherwise high impedance. Input Supply Voltage. Bypass VS to GND with a 0.1F capacitor. Open-Drain Fault Output. FLAG asserts low when a fault occurs at OUT1-OUT8. Exposed Paddle. Connect EP to ground plane.
MAX4896
7
SPLD
8 9 10, 16 11 12 13 14 15 17 18 19 20 --
OUT8 OUT7 PGND OUT6 OUT5 GND OUT4 OUT3 OUT2 OUT1 VS FLAG EP
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7
Heslington
Space-Saving, 8-Channel Relay/Load Driver MAX4896
Detail Description
The MAX4896 is an 8-channel relay and load driver for medium voltage applications up to 50V. The MAX4896 features built-in inductive kickback protection, drive for latching/nonlatching, or dual-coil relays and an internal register for detecting open-load and short-circuit faults. Each independent open-drain output features a 3 onresistance and is guaranteed to sink 400mA at VS 4.5V, and 100mA at VS 3.6V. The MAX4896 also incorporates a logic input (PDCD) that allows the device to continue operating when an overcurrent condition lasts longer than the 280s (max) fault delay time. A built-in overvoltage protection clamp handles kickback voltage transients, which are common when driving inductive loads. Thermal-shutdown circuitry shuts off all outputs (OUT_) when the junction temperature exceeds +160C. The MAX4896 employs a reset input that allows the user to turn off all outputs simultaneously with a single control line. The MAX4896 includes a 10MHz SPI-/QSPI-/MICROWIREcompatible serial interface. The serial interface is compatible with TTL-/CMOS-logic voltage levels and operates with a single +2.7V to +5.5V supply. high latches the data in the shift register to the output control register. DOUT is the output of the internal output status register for diagnostics purposes (see Figure 2 and Tables 2 and 3). Status data for each channel is transferred to the shift register at the falling edge of CS. The data bits contained in the shift register are then transferred to the DOUT output synchronously with SCLK's falling edge. While CS is low, the switches always remain in their previous states. Drive CS high after 8 bits of data have been shifted in to update the output state, and to further inhibit data from entering the shift register. When CS is high, transitions at DIN and SCLK have no effect on the output, and the first input bit (D7) is present at DOUT. If the number of data bits entered while CS is low is greater or less than 8, the shift register contains only the last 8 data bits, regardless of when they were entered. The 3-wire serial interface is compatible with SPI, QSPI, and MICROWIRE standards. The latch that drives the analog output stages is updated on the rising edge of CS, regardless of SCLK's state.
Diagnostic Information
The MAX4896 contains an internal output status register used for diagnostics information for each output (see Tables 1, 2, and 3). When a fault condition is detected at any channel for longer than the minimum fault-filtering time (tD(FAULT)_min), the fault information is latched into the corresponding position in the output status register (see Table 2), and the FLAG asserts. Status/diagnostics data for each channel in the output status register is transferred to the output shift register at the falling edge of CS. While CS is low, the diagnostics bits are then transferred to DOUT synchronously with SCLK's falling edge. A rising edge at CS resets the output status register data. During normal operation, the output status bit is the same as the DIN bit (DO1 = D1, DO2 = D2). When the MAX4896 is operating with a fault condition, the output status bit is the inverse of the DIN bit (DO1 = 0, D1 = 1).
Serial Interface
The serial interface consists of an 8-bit input shift register, a parallel latch (output control register) controlled by SCLK and CS, and an output status register containing diagnostics information. The input to the shift register is an 8-bit word. Each data bit controls one of the eight outputs, with the most significant bit (D7) corresponding to OUT8, and the least significant bit (D0) corresponding to OUT1 (see Table 1). When CS is low, data at DIN is clocked into the shift register synchronously with SCLK's rising edge. Driving CS from low to
OUTPUT STATUS REGISTER (OSR)
LATCHED ON CS: DIN SCLK CS LATCHED ON CS: 8-BIT SHIFT REGISTER DOUT
OUTPUT CONTROL REGISTER (OUT)
Figure 1. Serial Interface 8 _______________________________________________________________________________________
Space-Saving, 8-Channel Relay/Load Driver
Table 1. Serial-Input Address
DIN OUT_ D0 OUT1 D1 OUT2 D2 OUT3 D3 OUT4 D4 OUT5 D5 OUT6 D6 OUT7 D7 OUT8
MAX4896
Table 2. Serial-Output Address
DOUT OUT_ DO0 OUT1 DO1 OUT2 DO2 OUT3 DO3 OUT4 DO4 OUT5 DO5 OUT6 DO6 OUT7 DO7 OUT8
Table 3. Status-Register Output Diagnostic
OUTPUT STATUS Off Off On On DO_ STATUS BIT Low High Low High DIAGNOSTIC Normal operation. Fault condtion. Output open or short circuit. Fault condition. Short circuit to positive load voltage. Normal operation.
CS tCSS SCLK tDH tDS DIN D7 D6 D1 tDO DOUT tON, tOFF OUT_ D0 tCL tCH tCSH
tCSW tCSO
Figure 2. 3-Wire Serial-Interface Timing
_______________________________________________________________________________________
9
Space-Saving, 8-Channel Relay/Load Driver MAX4896
The minimum fault-filtering time helps mask short-duration fault conditions, such as driving highly capacitive loads. The typical diagnostics software routine works as follows: * Write data to the MAX4896 * Wait for tD(FAULT) maximum to ensure diagnostics data is ready and valid * Write same data to the MAX4896 and read out the diagnostics data from the shift register Use Table 3 to diagnose the output state. To reduce processor overhead, an interrupt-based diagnostics routine is possible. The diagnostics routine will analyze diagnostics data only when the FLAG output triggers an interrupt. Output Short-Circuit/Current-Limiting Protection The MAX4896 channels (OUT_) are protected against short-circuits conditions. When the channel's output current exceeds the current-limit threshold (ILIM) for longer than the minimum fault-filtering time (tD(FAULT) min), the short-circuit protection is activated. The shortcircuit protection behavior is determined by the logic level at SPLD. When SPLD = high, an overloaded channel remains in a current-limited state until the short-circuit condition is removed or thermal shutdown is reached. This allows the operation of loads where the inrush currents may exceed the MAX4896 internal current limit. When SPLD = low, an overloaded channel immediately turns off (latched-off). When a shorted output is latched off, the channel can be turned back on after the next serial input data is latched into the MAX4896. Open-Load Detection The MAX4896 features an output pulldown current source, along with a voltage comparator, to detect an open-load fault condition. To enable the open-load detection function, PDCD must be low. The voltage at OUT_ is compared with the diagnostics threshold voltage (VDS(OL)) to determine whether a open-load fault condition exists.
Thermal Shutdown
If the junction temperature exceeds +160C, all outputs are switched off immediately (no filtering time) and FLAG asserts. The hysteresis is approximately +20C, disabling thermal shutdown once the temperature drops below +140C.
RESET
The MAX4896 features an asynchronous reset input that allows the user to simultaneously turn all outputs off using a single control line. Drive RESET low to clear all latches and registers, and to turn off all outputs. While RESET is low, the OUT pulldown currents are disabled, regardless of the state of PDCD.
FLAG Output
FLAG is an open-drain latched output that can be connected to a P interrupt and pulls low whenever a fault condition (short-circuit and/or open-load) is detected in any of the eight outputs for longer than the minimum fault-filtering time (tD(FAULT) min). FLAG asserts immediately, (no filtering time), when a thermal-shutdown fault condition is detected. The latch FLAG deasserts on CS rising edge.
Applications Information
Daisy Chaining
The MAX4896 features a digital output (DOUT) that provides a simple way to daisy chain multiple devices. This feature allows the user to drive large banks of relays using only a single serial interface. To daisy chain multiple devices, connect all CS inputs together and connect the DOUT of one device to the DIN of another device (see Figure 3). During operation, a stream of serial data is shifted through all the MAX4896s in series.
Inductive Kickback Protection
Each output features an output protection clamp, limiting the OUT voltage to 65V (typ). The clamp protects against voltage transient when driving inductive loads.
10
______________________________________________________________________________________
Space-Saving, 8-Channel Relay/Load Driver MAX4896
VS
0.1F
VS
0.1F
DEVICE 1 VS DIN DIN DOUT
DEVICE 2 VS DIN DOUT
MAX4896
SCLK SCLK
OUT1 SCLK OUT8
MAX4896
OUT1
OUT8 CS GND PGND
CS
GND
PGND
CS
Figure 3. Daisy-Chain Configuration
Functional Diagram
VS PDCD SPLD
CLAMP GATE CONTROL AND CURRENT LIMITING 8-BIT LATCH OPEN / SHORT DETECT CHANNEL 1 SPI/CONTROL INTERFACE DIN DOUT CHANNEL 5 SCLK CS FLAG OVERTEMPERATURE PROTECTION CHANNEL 6 CHANNEL 7 CHANNEL 8 CHANNEL 2 CHANNEL 3 CHANNEL 4
OUT1
RESET
OUT2 OUT3 OUT4 OUT5 OUT6 OUT7 OUT8
MAX4896
GND PGND
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11
Space-Saving, 8-Channel Relay/Load Driver MAX4896
Pin Configuration
PROCESS: BiCMOS
OUT3 OUT4 OUT5 OUT6 GND
Chip Information
TOP VIEW
15 PGND 16 OUT2 17 OUT1 18 VS 19 FLAG 20
14
13
12
11 10 9 PGND OUT7 OUT8 SPLD PDCD
MAX4896
+
*EP
8 7 6
1 RESET
2 CS
3 DIN
4 SCLK
5 DOUT
TQFN 5mm x 5mm *EXPOSED PADDLE. CONNECT TO PGND.
12
______________________________________________________________________________________
Space-Saving, 8-Channel Relay/Load Driver
Package Information
QFN THIN.EPS
MAX4896
____________________Revision History
Pages changed at Rev 1: 1, 12, 13, 14
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13
Space-Saving, 8-Channel Relay/Load Driver MAX4896
Package Information (continued)
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.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
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