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19-4119; Rev 1; 1/10
KIT ATION EVALU BLE AVAILA
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
General Description
The MAX9921 provides a single chip solution to interface two 2-wire Hall-effect sensors to a low-voltage microprocessor (P). This device supplies and monitors the current drawn by two Hall-effect sensors, filters the sensed current level, and outputs the corresponding logic level. The MAX9921 includes input diagnostics and fault protection. These features allow the device to determine fault conditions such as open inputs, inputs shorted to the battery, and inputs shorted to ground. If the MAX9921 detects any of these conditions at either IN1 or IN2, the device shuts off the current to the corresponding input. The MAX9921 protects the Hall sensors from supply transients up to 60V at the BAT supply. Normal operating supply voltage ranges from 6V to 18V. If the battery voltage is out of range, the MAX9921 shuts off the current to the Hall sensors. The MAX9921 provides an 80s blanking time following Hall sensor power-up or restart. The open-drain logic outputs are compatible with logic levels up to 5.5V. The MAX9921 is available in a small 10-pin MAX(R) package and is specified over the -40C to +125C automotive temperature range.
Features
o Withstands 60V at BAT Supply and Hall Inputs o 6V to 18V Operating Voltage Range o Provides Supply Current and Interfaces to Two 2-Wire Hall Sensors o Error Output with Diagnostics of Hall Inputs and BAT Voltage o Protects Hall Sensors from Overvoltage by Isolating Them from Supply Transients o Hall Inputs Protected from Short to Ground o Ramps Current to Hall Sensors at 4mA/s o Output Enable Input Allows Multiplexing of Outputs from Multiple MAX9921s o Hall Output Filtering o Hall Sensor Blanking Following Hall Sensor Power-Up or Restart o Low-Power Shutdown, Controlled with OE and DIAG Inputs o Operates with 2V Ground Shifts Between Hall Sensor and MAX9921
MAX9921
Ordering Information
PART MAX9921AUB+T MAX9921AUB/V+T TEMP RANGE -40C to +125C -40C to +125C PIN-PACKAGE 10 MAX 10 MAX
Applications
Door Modules Window Lifters Seat Movers Electric Sunroofs Powered Lift Gate Controllers Powered Running Boards Seatbelt Buckles
+Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. /V denotes an automotive qualified part. Pin Configuration appears at end of data sheet.
Typical Application Circuit
VBAT: 6V TO 18V OPERATING, WITHSTANDS 60V BATTERY E C U C O N N E C T O R RISET = 63.4k, 1% BAT ISET REF GENERATION, DIAGNOSTICS AND OVERVOLTAGE DETECT 0.01F IN1 FILTER 0.01F IN2 FILTER GND 10k 0.1F 3.3V TO 5V
N S REMOTE GROUND
CONTROL
OE ERR
VCC
DIAG OUT1
P/LOGIC CIRCUIT
N S REMOTE GROUND
MAX9921
OUT2 GND
MAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products 1
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
ABSOLUTE MAXIMUM RATINGS
BAT to GND............................................................-0.3V to +60V ISET to BAT ...........................................................-2.0V to +0.3V IN1, IN2 to GND..........-5.0V to the lower of +60V or (VBAT + 1V) DIAG, OE to GND..................................................-0.3V to +6.0V OUT1, OUT2, ERR to GND....................................-0.3V to +6.0V Short-Circuit Duration of OUT1, OUT2, ERR to GND or to 5.5V (individually)............................................Continuous Current into Any Pin Except IN1, IN2 ...............................20mA Current into IN1, IN2.......................................................100mA Continuous Power Dissipation (TA = +70C) 10-Pin MAX (derate 5.6mW/C above +70C) .........444.4mW 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.
DC ELECTRICAL CHARACTERISTICS
(VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4k, RPU = 10k at ERR, OUT1 and OUT2, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER GENERAL BAT Supply Range VBAT Low for ERR Output Active VBAT High for ERR Output Active BAT Supply Current HALL INPUTS (IN1 and IN2) Input Current for Output High Input Current for Output Low Input Current Hysteresis for High/Low Detection Input Pullup Impedance Input Voltage Interpreted as Shorted to Battery Current Range Interpreted as Open Circuit Current Level Interpreted as Shorted Sensor to Ground IIH IIL IIN,HYS RPU VSB IOC Not a sustained RISET = 63.4k condition, reverts to 50A when detected RISET = 59.0k RISET = 63.4k RISET = 59.0k RISET = 63.4k RISET = 59.0k RISET = 63.4k RISET = 59.0k VBAT = 6V, inputs IN1, IN2 with IIN = -14mA Measured with respect to VBAT -2 -7.2 -7.8 0.76 0.78 50 100 +0.02 -23 mA -25 -11.5 -12.4 mA mA mA mV mA VBAT VBL VBH IBAT ISD Normal mode Shutdown mode, VOE = VDIAG = 0V 1 6 5.2 22 1.3 1 18 V V V mA A SYMBOL CONDITIONS MIN TYP MAX UNITS
ISC
2
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
DC ELECTRICAL CHARACTERISTICS (continued)
(VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4k, RPU = 10k at ERR, OUT1 and OUT2, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Output Voltage Low (ERR, OUT1, OUT2) Three-State Output Current (ERR, OUT1, OUT2) Input-Voltage High (DIAG, OE) Input-Voltage Low (DIAG, OE) Input Resistance to GND (DIAG, OE) SYMBOL CONDITIONS MIN TYP MAX UNITS LOGIC I/O (OUT1, OUT2, ERR, DIAG, and OE) VOL IOZ VIH VIL RIN 50 80 Sink current = 1mA VOE = 0V, 0 VOUT_ 5V 2.1 0.8 0.4 1 V A V V k
MAX9921
AC TIMING CHARACTERISTICS
(VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4k, RPU = 10k at ERR, OUT1 and OUT2, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2, and 4)
PARAMETER IN1, IN2 Blanking Time at Hall Switch Power-Up IN1, IN2 Current Ramp Rate After Turn-On Delay from IN_ to OUT_ (Filter Delay) Delay from IN_ Fault to ERR Delay from DIAG High to OUT_ and ERR Delay from DIAG Low to OUT_ and ERR Delay Difference Between Rising and Falling Edges for Both Channels Delay Difference Between Channels Maximum Frequency on Hall Inputs IN_ Pulse Length Rejected by Filter to OUT_ SYMBOL tBL tRAMP tDEL tERR tDLH tDHL CONDITIONS IIH = -11.5mA to GND, time from VIN_ = 500mV until OUT_ high, CL = 20pF (Note 3) VIN = GND From IIH to IIL or from IIL to IIH, CL = 20pF, Figure 1 From IIL to ISC or from IIH to IOC, falling edge only, CL = 20pF, Figure 1 Rising edge of DIAG to falling or rising edge of outputs, CL = 20pF, Figure 1 Falling edge of DIAG to falling or rising edge of outputs, CL = 20pF, Figure 1 CHALL-BYPASS = 0.01F, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF CHALL-BYPASS = 0.01F, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF CHALL-BYPASS = 0.01F, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF Figure 2 50 5.5 MIN 50 3.8 6.5 31 350 1.6 TYP MAX 140 UNITS s mA/s s ns ns s
tDM
20
ns
tCC fMAX PR
100
ns kHz s
Note 1: All DC specifications are 100% tested at TA = +25C. AC specifications and specifications over -40C to +125C are guaranteed by design. Note 2: CL is external load capacitance on the outputs for test only. Note 3: These blanking times apply when the MAX9921 is operating in normal mode. Blanking times following power-up or startup from shutdown mode are 20s longer. Note 4: The following AC parameters change with the value of RISET: tBL, tRAMP, tDEL, fMAX, and PR. The typ values given are for RISET = 63.4k. The parameters tRAMP and fMAX increase 8%, and tDEL and PR decrease 8% with RISET = 59.0k. The limits for tBL and fMAX apply for both resistor values.
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3
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
Timing Diagrams
APPROX. 50mA RETRY SHORT CIRCUIT 14mA IN 1 7mA HALL SENSOR OPEN CIRCUIT tDEL 5V OUT1 0V 4mA/s
0mA
5V OUT2 0V tERR 5V ERR 0V tERR
5V DIAG 0V
Figure 1. Timing Diagram
4
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Timing Diagrams (continued)
MAX9921
PR
PR
14mA IN_ 7mA
0mA
5V OUT_ 0V
tDEL
tDEL
Figure 2. Hall Input Pulse Rejection
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5
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
Typical Operating Characteristics
(VBAT = 14V, TA = +25C, unless otherwise noted.)
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
MAX9921 toc01
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
MAX9921 toc02
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
TA = +125C 1.5 1.4 BAT CURRENT (mA) 1.3 1.2 1.1 1.0 0.9 0.8 19.0 19.5 20.0 20.5 BAT VOLTAGE (V) 21.0
MAX9921 toc03
1.4 TA = -40C 1.3 1.2 BAT CURRENT (mA) 1.1 1.0 0.9 0.8 0.7 0.6 19.0 19.5 20.0 20.5 BAT VOLTAGE (V)
1.4 TA = +25C 1.3 1.2 BAT CURRENT (mA) 1.1 1.0 0.9 0.8 0.7 0.6
1.6
21.0
19.0
19.5
20.0 20.5 BAT VOLTAGE (V)
21.0
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
MAX9921 toc04
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
MAX9921 toc05
BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE
TA = +125C 1.4 BAT CURRENT (mA)
MAX9921 toc06
1.3 TA = -40C 1.2 BAT CURRENT (mA) 1.1 1.0 0.9 0.8 0.7 0.6 OPERATING MODE HALL INPUTS DISABLED
1.3 TA = +25C 1.2 BAT CURRENT (mA) 1.1 1.0 0.9 0.8 HALL INPUTS DISABLED 0.7 OPERATING MODE 0.6
1.6
1.2
1.0
0.8
OPERATING MODE HALL INPUTS DISABLED
0.6 5 10 15 20 25 30 35 40 45 50 55 60 BAT VOLTAGE (V) 5 10 15 20 25 30 35 40 45 50 55 60 BAT VOLTAGE (V)
5 10 15 20 25 30 35 40 45 50 55 60 BAT VOLTAGE (V)
BAT SUPPLY CURRENT vs. VBAT IN SHUTDOWN MODE
MAX9921 toc07
HALL INPUT CURRENT HYSTERESIS FOR HIGH/LOW THRESHOLDS vs. TEMPERATURE
9.8 HALL INPUT CURRENT (mA) 9.6 9.4 9.2 9.0 8.8 8.6 8.4 8.6 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) LOW THRESHOLD HIGH THRESHOLD
MAX9921 toc08
HALL INPUT CURRENT HYSTERESIS FOR HIGH/LOW THRESHOLD vs. VBAT
MAX9921 toc09
50 45 40 BAT CURRENT (nA) 35 30 25 20 15 10 5 0 0 10 20 30 BAT VOLTAGE (V) TA= -40C TA = +125C TA = +25C
10.0
9.8 9.6 HALL INPUT CURRENT (mA) 9.4 9.2 LOW THRESHOLD 9.0 8.8 HIGH THRESHOLD
40
6
8
10 12 14 BAT VOLTAGE (V)
16
18
6
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Typical Operating Characteristics (continued)
(VBAT = 14V, TA = +25C, unless otherwise noted.)
IN_ BLANKING TIME AT HALL SWITCH POWER-UP vs. TEMPERATURE
MAX9921 toc10
MAX9921
IN_ CURRENT RAMP RATE AFTER TURN-ON vs. TEMPERATURE
MAX9921 toc11
DELAY FROM IN_ TO OUT_ (FILTER DELAY) vs. TEMPERATURE
MAX9921 toc12
100 95 IN_ BLANKING TIME (s) 90 85 80 75 70 65 60
5 IN_ CURRENT RAMP RATE (mA/s)
10
4
9
DELAY (s) -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
3
8
2
7
1
6
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
DELAY FROM IN_ FAULT TO ERR (FILTER DELAY) vs. TEMPERATURE
MAX9921 toc13
DELAY DIFFERENCE BETWEEN RISING AND FALLING EDGES FOR BOTH CHANNELS vs. TEMPERATURE
160 DELAY DIFFERENCE (ns) 140 120 100 80 60 40 20 IN1 AND IN2
MAX9921 toc14
DELAY DIFFERENCE BETWEEN CHANNELS vs. TEMPERATURE
MAX9921 toc15
50
180
250
40
200 DELAY DIFFERENCE (ns)
DELAY (s)
30
150
20
100
10
50
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
MAXIMUM FREQUENCY ON HALL INPUTS vs. TEMPERATURE
MAX9921 toc16
IN_ PULSE LENGTH REJECTED BY FILTER TO OUT_ vs. TEMPERATURE
MAX9921 toc17
VBAT UNDERVOLTAGE THRESHOLD vs. TEMPERATURE
6.1 6.0 VBAT THRESHOLD (V) 5.9 5.8 5.7 5.6 5.5 5.4 VBAT FALLING, ERR GOES LOW VBAT RISING, ERR GOES HIGH
MAX9921 toc18
100 95 90 FREQUENCY (kHz) 85 80 75 70 65 60 55 50 IN1 AND IN2, 50% DUTY CYCLE
7 6 PULSE LENGTH (s) 5 4 3 2 1 0 IN1 AND IN2 WITH POSITIVE PULSE
6.2
IN1 AND IN2 WITH NEGATIVE PULSE
5.3 5.2 -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)
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7
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
Typical Operating Characteristics (continued)
(VBAT = 14V, TA = +25C, unless otherwise noted.)
VBAT OVERVOLTAGE THRESHOLD vs. TEMPERATURE
20.4 20.3 VBAT THRESHOLD (V) 20.2 20.1 20.0 19.9 19.8 19.7 19.6 19.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VBAT RISING, ERR GOES HIGH VBAT FALLING, ERR GOES LOW
MAX9921 toc19
INPUT PULLUP RESISTANCE vs. VBAT
70 INPUT PULLUP RESISTANCE () 60 50 40 30 20 10 0 6 9 12 VBAT (V) 15 18 TA = -40C TA = +125C TA = +25C
MAX9921 toc20 MAX9921 toc22
20.5
80
THRESHOLD CURRENT vs. ISET RESISTOR
CHANGE IN THRESHOLD CURRENT (%) INPUT CURRENT FOR OUTPUT HIGH AND INPUT CURRENT FOR OUTPUT LOW
MAX9921 toc21
RESPONSE OF INPUT TO SHORT TO GROUND
VIN1 10V/div 0V
15 10 5 0 -5 -10 -15 -15 -10 -5 0 5 10 CHANGE IN ISET RESISTOR (%) HYSTERESIS
VERR 5V/div 0V IIN1 25mA/div 0A
15
10s/div
STARTUP OF HALL INPUT FROM SHUTDOWN
MAX9921 toc23
VIN_ 10V/div BLANKING PERIOD VOUT_ VOE_ IIN_ 5V/div 10mA/div 5V/div
20s/div
8
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Pin Description
PIN 1 NAME BAT FUNCTION Battery Power Supply. Connect BAT to the positive supply through an external reverse-polarity diode. Bypass BAT to ground with a 0.1F capacitor. Current-Setting Input. Connect a 63.4k, 1% resistor (RISET) between BAT and ISET to set the standard current thresholds for Hall current sensing. Make no other connections to ISET. All routing must have low parasitic capacitance. Hall-Effect Sensor Input 1. Bypass IN1 to BAT or GND with a 0.01F capacitor. Terminate an unused input with a 1.5k resistor from IN1 to GND to prevent false error diagnostics. Hall-Effect Sensor Input 2. Bypass IN2 to BAT or GND with a 0.01F capacitor. Terminate an unused input with a 1.5k resistor from IN2 to GND to prevent false error diagnostics. Ground Open-Drain Output Signal 2. OUT2 is the signal translated from Hall Sensor 2. Connect a 10k or larger pullup resistor to logic supply. Open-Drain Output Signal 1. OUT1 is the signal translated from Hall Sensor 1. Connect a 10k or larger pullup resistor to logic supply. Open-Drain Diagnostic and Error Output. Connect a 10k or larger pullup resistor to logic supply. If DIAG is asserted low, a high on ERR indicates that there is no fault while a low on ERR indicates that either the battery voltage is out of range or there is a fault condition. If DIAG is high, ERR provides diagnostic information in conjunction with OUT1 and OUT2. See Tables 1 and 2. If OE is low or while in shutdown, ERR is high impedance. Output Enable Input. OE has an internal 80k resistor to GND. Drive OE high to enable the outputs ERR, OUT1, and OUT2. Drive OE low to place the outputs in high impedance. If OE and DIAG are both low for more than 40s, the device enters shutdown and all outputs are in high impedance. While in shutdown, if either OE or DIAG transitions low to high, the device exits shutdown mode. Diagnostic Enable Input. DIAG has an internal 80k resistor to GND. Drive DIAG low for normal operation. In this mode, ERR, OUT1, and OUT2 provide Hall sensor information. Drive DIAG high for diagnostic operation. A high-tolow transition initiates an attempt to restart, with a blanking cycle any Hall input that has been shut down. See Tables 1 and 2 (diagnostic truth tables). If OE and DIAG are both low for more than 40s, the device enters shutdown mode with all outputs in high impedance. While in the shutdown mode, if either OE or DIAG transitions low to high, the device exits shutdown mode.
MAX9921
2
ISET
3 4 5 6 7
IN1 IN2 GND OUT2 OUT1
8
ERR
9
OE
10
DIAG
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9
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
Functional Diagram
BAT DIAG REF GENERATION, DIAGNOSTICS, AND OVERVOLTAGE DETECT ERR
Hall Input Diagnostic
Normal Mode In normal mode, DIAG is driven low. In this case, if ERR is high, the outputs (OUT1 and OUT2) indicate the high or low state of the corresponding Hall sensors (IN1 and IN2). In normal mode, a low ERR indicates a fault. If ERR is low, the outputs may be pulled low and may not indicate the high or low state of the Hall sensors. This can happen during the power-up, restart, or blanking cycles of the Hall inputs, or due to a fault on one or both of the Hall inputs, or when VBAT is out of range, while the error output is low. If one output continues signaling and the other output is low, the output with the low logic-level indicates a fault or a restart and blanking cycle on the corresponding Hall input. Table 1 summarizes normal mode operation. Diagnostic Mode When DIAG is driven high, the MAX9921 enters diagnostic mode. In this mode, OUT1 and OUT2 output diagnostic information. IN1 takes precedence over IN2. IN2's diagnostics remain masked until a fault on IN1 is cleared. For diagnostics and troubleshooting, when IN1 or IN2 shuts off due to an input short to ground, it continues to source 50A. A falling edge at DIAG restarts a Hall input that has been shut off due to a short to ground. Diagnostic indications are never latched internally and they indicate the real-time state of IN1 or IN2. Table 2 summarizes diagnostic mode operation.
ISET
CONTROL OE
IN1 FILTER
MAX9921
OUT1
IN2 FILTER GND OUT2
Detailed Description
The MAX9921 connects two 2-wire Hall-effect sensors to a low-voltage P. This device supplies current through IN1 and IN2 to Hall sensors and monitors the current level drawn by the Hall sensors. The MAX9921 outputs a high or low logic-level to the corresponding open-drain output (OUT1 or OUT2). If the current flowing out of either IN1 or IN2 exceeds the high input current threshold, the corresponding output goes high. If the current flowing out of either IN1 or IN2 is lower than the low input current threshold, the corresponding output goes low.
Hall Input Fault Detection
If a fault is detected, the ERR output is asserted low to notify the P. This condition can occur due to the Hall input being shorted to ground, shorted to battery, or open.
Table 1. Diagnostic Truth Table (Normal Mode)
INPUT DIAG 0 ERR 1 OUTPUT OUT1 0 or 1 OUT2 0 or 1 DIAGNOSIS OUT1 and OUT2 indicate state of IN1 and IN2, respectively Fault on IN1 and/or IN2, or VBAT out of range, or power-up or restart blanking (unknown current level of IN1 and IN2) Fault on IN1 or restart blanking of IN1 Fault on IN2 or restart blanking of IN2 COMMENT Normal mode: No fault indication (outputs indicate Hall sensor high or low status) Normal mode: ERR asserted low indicates fault (outputs may no longer indicate the high or low state of the Hall sensors) Normal mode: ERR asserted low indicates fault; Hall output 2 continues signaling Normal mode: ERR asserted low indicates fault; Hall output 1 continues signaling
0
0
0
0
0 0
0 0
0 0 or 1
0 or 1 0
10
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Table 2. Diagnostic Truth Table (Diagnostic Mode)
INPUT DIAG 1 1 1 1 1 1 1 1 ERR 0 0 0 0 1 1 1 1 OUTPUT OUT1 0 0 1 1 0 0 1 1 OUT2 0 1 0 1 0 1 0 1 No fault IN1 open circuit, or IN1 open circuit and fault on IN2 IN1 shorted to battery, or IN1 shorted to battery and fault on IN2 IN1 shorted to ground, or IN1 shorted to ground and fault on IN2 VBAT out of range, or power-up or restart and blanking cycle (dominant fault masks all other faults) IN2 open circuit IN2 shorted to battery IN2 shorted to ground DIAGNOSIS
MAX9921
Hall Sensor Protection from Supply Transients If the VBAT voltage is lower than 6V or exceeds 18V, IN1 and IN2 shut off current to both Hall sensors and ERR, OUT1, and OUT2 go low. When VBAT returns to the proper range, both IN1 and IN2 restart, following a blanking cycle. Hall Inputs Open Condition If either IN1 or IN2 is open (IIN < 2mA), the corresponding input shuts off current to the Hall sensor. If IN1 or IN2 is loaded, it exits the open input fault condition and restarts the corresponding Hall input, following a blanking cycle.
Hall Input Shorted to Battery If either IN1 or IN2 is shorted to the battery (VIN > VBAT + 100mV), the MAX9921 shuts off current to the corresponding Hall sensor. In this case, if IN1 or IN2 is more than 1V above VBAT, it may back-drive current into BAT. In such a condition, the current level in the Hall input should not exceed 100mA. Therefore, all the MAX9921s together can share a separate reversepolarity protection diode to avoid powering up other circuitry sharing a common diode (Figure 3).
BATTERY
REVERSE-POLARITY DIODE FOR MAX9921s RISET RISET
REVERSE-POLARITY DIODE FOR OTHER CIRCUITRY
MAX9921
BAT ISET IN1 IN2 GND DIAG OE ERR OUT1 OUT2 BAT ISET IN1 IN2 GND
MAX9921
DIAG OE ERR OUT1 OUT2
BAT
OTHER CIRCUITRY
GND
Figure 3. Several MAX9921s Connected to a Common Reverse-Polarity Diode
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Hall Input Short-to-Ground The Hall input shorted-to-ground fault is effectively a latched condition if the input remains loaded by the Hall switch when the shorting condition is removed. The current required to power the Hall switch is shut off and only a 50A pullup current remains. The Hall input can be manually re-energized or it can be re-energized by the ECU. A falling edge at DIAG initiates a restart with a blanking cycle of any Hall input that has been shut down due to the shorted-to-ground condition. During startup or restart, it is possible for a Hall input to charge up an external capacitance of 0.02F without tripping into a shortedto-ground latched state. All other fault conditions are not latched and when these other faults are removed, ERR goes high and the Hall input is again functional. Manual Method for Re-Energizing Hall Sensor and Means for Diagnosing an Intermittent Hall Sensor Connection Figure 4 shows the behavior of the MAX9921 when a Hall input is open. Figure 5 shows the behavior of the MAX9921 when the open input is reconnected to a Hall sensor. Figures 4 and 5 demonstrate how a shorted-toground Hall input can be reset.
MAX9921
Resetting a shorted-to-ground Hall input involves three steps: 1) Relieve the short to ground at the Hall sensor. 2) Disconnect the Hall input from the Hall sensor (open input fault condition). 3) Reconnect the Hall input to the Hall sensor. The MAX9921 restarts the Hall input with a blanking cycle. If the Hall input is disconnected from the Hall sensor for 10ms, it allows the Hall input to be pulled up by the 50A pullup current to register the open-input fault condition. Then, reconnecting the Hall input to the Hall sensor restarts the Hall input with a blanking cycle. This provides a manual means of re-energizing a Hall input without having to resort to the ECU to reset it. This also demonstrates that an intermittent connection to a Hall sensor can recover without intervention of the ECU. This gives the ECU a means of diagnosing an intermittent connection to a Hall sensor by using the diagnostic mode to detect a diagnostic sequence of "open-circuit" to "blanking cycle" to "no fault."
14V HALL INPUT SHORT TO GROUND FAULT INDICATED 5mV/ms HALL INPUT DISCONNECTED FROM SENSOR 0V TIME HALL INPUT OPEN-CIRCUIT FAULT INDICATED
VIN_
VBAT - 25mV
IIN_ 50A
0A TIME
Figure 4. Hall Input Ramps to Open-Circuit Fault When Short to Ground is Relieved
12
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
14V
VIN_
VBAT - 500mV 8V
HALL INPUT RECONNECTED TO HALL SENSOR 0V TIME
11.5mA
IIN_ 4mA/s
0A TIME
Figure 5. Hall Input Re-Energized When Open Input is Reconnected to Hall Sensor
Table 3. Summary of Fault Protection and Recovery
MAX9921 ACTIONS FAULT DESCRIPTION VBAT < 6V VBAT > 18V CRITERION ERR OUTPUT Asserted low Asserted low HALL INPUT RESPONSE Shutoff current to both Hall sensors Shutoff current to both Hall sensors Shutoff current to corresponding Hall sensor COMMENT/RECOVERY Both IN1 and IN2 are restarted with blanking cycle when VBAT returns to proper range. Both IN1 and IN2 are restarted with blanking cycle when VBAT returns to proper range. When a Hall input is again loaded, terminating open input condition, the Hall input are restarted with blanking cycle. If a Hall input is pulled more than 1V above VBAT, the input may back drive current into the BAT supply and pull VBAT up with it. In this condition, current levels in the Hall inputs should never exceed 100mA. For this reason, it is recommended that one or more MAX9921s be powered together and share a reverse-polarity diode separate from other circuitry. A falling edge at DIAG initiates a restart with a blanking cycle of any Hall input that has been shut off due to a short to ground. See the Hall Input Short-to-Ground section.
-- --
Hall input open
IIN < 2mA
Asserted low
Hall input shorted to battery
VIN > VBAT due to external reverse-battery Asserted low protection diode
Shutoff current to corresponding Hall sensor
Hall input shorted to ground
IIN > 23mA
Asserted low
Shutoff current to corresponding Hall sensor. 50A of pullup current is sourced to IN1 or IN2 to aid in troubleshooting.
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13
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
a higher current range which correspond to the selection of the R ISET resistor value. This makes the MAX9921 compatible with a wide array of 2- and 3-wire Hall sensors.
R
MAX9921
Hall Input Bypass Capacitor
The MAX9921 is optimized for use with external protection 0.01F capacitors from both IN1 and IN2 to BAT. These are essential to ensure robustness against automotive transients. These capacitors may be tied to GND instead of to BAT, but the connection to BAT is recommended.
x_
VCC
IN_ GND
Low-Voltage Operation
Figure 6. 3-Wire Hall-Effect Switches Configured as 2-Wire
Applications Information
Hall-Effect Sensor Selection
The MAX9921 is optimized for use with 2-wire Halleffect switches or with 3-wire Hall-effect switches connected as 2-wire (Figure 6). When using a 3-wire Hall sensor, the resistor R is chosen so that the current drawn by the Hall sensor crosses the MAX9921 current threshold when the magnetic threshold of the Hall sensor is exceeded. Table 4 shows a partial list of Hall sensors (primarily 2wire) that can be used with the MAX9921. The DC Electrical Characteristics Table gives tested IIH/IIL current threshold limits for both a lower current range and
To ensure correct operation of the Hall sensor at low input voltages, it is important to consider the voltage drop of the MAX9921 with low battery voltages. This dropout voltage can be calculated using the formula: VDROPOUT = IHALL x RPU IHALL is the maximum current which must be supplied to the Hall sensor and RPU is the internal resistance of the MAX9921, nominally 50 (see the Input Pullup Resistance vs. VBAT graph in the Typical Operating Characteristics). As an example, assume the use of a HAL573 sensor, which draws a maximum current of 17mA. The dropout voltage is then 850mV and the approximate minimum voltage supplied to the Hall sensor is 6V - 0.85V = 5.15V, which is higher than the minimum operating voltage of 3.75V specified for the HAL573.
Table 4. Partial List of Compatible Hall Switches
PART HAL573-6 HAL556/560/566 HAL581/584 A1140/1/2/3 A1180/81/82/83 MANUFACTURER Micronas Micronas Micronas Allegro Allegro WEBSITE www.micronas.com www.micronas.com www.micronas.com www.allegromicro.com www.allegromicro.com 2-wire 2-wire 2-wire 2-wire 2-wire COMMENT
Note: The Hall switches listed above are supported by the MAX9921 using RISET = 63.4k.
14
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Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics
Pin Configuration
TOP VIEW
BAT 1 ISET IN1 IN2 GND 2 3 4 5 10 DIAG 9 OE ERR OUT1 OUT2
Chip Information
PROCESS: BiCMOS
MAX9921
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE 10 MAX PACKAGE CODE U10+2 DOCUMENT NO. 21-0061
MAX9921
8 7 6
MAX
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15
Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921
Revision History
REVISION NUMBER 0 1 REVISION DATE 6/08 1/10 Initial release Added limits to show compatibility with second set of Hall sensor thresholds, removed TLE4941/C from list of recommended Hall sensors, and added automotive part DESCRIPTION PAGES CHANGED -- 1, 2, 14
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) 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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