19-4119; Rev 1; 1/10 KIT ATION EVALU E L B AVAILA Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics 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/µs 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 The MAX9921 provides a single chip solution to interface two 2-wire Hall-effect sensors to a low-voltage microprocessor (µP). 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 80µs 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 µMAX® package and is specified over the -40°C to +125°C automotive temperature range. Ordering Information PART Applications Door Modules Window Lifters Powered Lift Gate Controllers Powered Running Boards Seat Movers Electric Sunroofs TEMP RANGE PIN-PACKAGE MAX9921AUB+T -40°C to +125°C 10 µMAX MAX9921AUB/V+T -40°C to +125°C 10 µMAX +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. Seatbelt Buckles Typical Application Circuit VBAT: 6V TO 18V OPERATING, WITHSTANDS 60V S REMOTE GROUND N S 3.3V TO 5V BAT BATTERY N 0.1μF RISET = 63.4kΩ, 1% ISET E C U C O N N E C T O R 10kΩ REF GENERATION, DIAGNOSTICS AND OVERVOLTAGE DETECT CONTROL OE VCC ERR 0.01μF DIAG IN1 μP/LOGIC CIRCUIT OUT1 FILTER 0.01μF IN2 MAX9921 FILTER OUT2 GND GND REMOTE GROUND µMAX is a registered trademark of Maxim Integrated Products, Inc. ________________________________________________________________ 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. 1 MAX9921 General Description MAX9921 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics 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 = +70°C) 10-Pin µMAX (derate 5.6mW/°C above +70°C) .........444.4mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +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. DC ELECTRICAL CHARACTERISTICS (VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4kΩ, RPU = 10kΩ at ERR, OUT1 and OUT2, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 18 V GENERAL BAT Supply Range VBAT 6 VBAT Low for ERR Output Active VBL 5.2 VBAT High for ERR Output Active VBH BAT Supply Current IBAT Normal mode ISD Shutdown mode, VOE = VDIAG = 0V V 1 22 V 1.3 mA 1 µA HALL INPUTS (IN1 and IN2) Input Current for Output High IIH Input Current for Output Low IIL Input Current Hysteresis for High/Low Detection IIN,HYS RISET = 63.4kΩ -11.5 RISET = 59.0kΩ -12.4 RISET = 63.4kΩ -7.2 RISET = 59.0kΩ -7.8 0.76 RISET = 59.0kΩ 0.78 RPU VBAT = 6V, inputs IN1, IN2 with IIN = -14mA Input Voltage Interpreted as Shorted to Battery VSB Measured with respect to VBAT Current Range Interpreted as Open Circuit IOC Current Level Interpreted as Shorted Sensor to Ground ISC 2 mA RISET = 63.4kΩ Input Pullup Impedance mA mA Ω 50 -2 Not a sustained RISET = 63.4kΩ condition, reverts to 50µA when detected RISET = 59.0kΩ _______________________________________________________________________________________ 100 mV +0.02 mA -23 mA -25 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics (VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4kΩ, RPU = 10kΩ at ERR, OUT1 and OUT2, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS LOGIC I/O (OUT1, OUT2, ERR, DIAG, and OE) Output Voltage Low (ERR, OUT1, OUT2) VOL Sink current = 1mA 0.4 V Three-State Output Current (ERR, OUT1, OUT2) IOZ VOE = 0V, 0 ≤ VOUT_ ≤ 5V ±1 µA Input-Voltage High (DIAG, OE) VIH Input-Voltage Low (DIAG, OE) VIL Input Resistance to GND (DIAG, OE) RIN 2.1 V 0.8 50 80 V kΩ AC TIMING CHARACTERISTICS (VBAT = 13.6V, VDIAG = 0, VOE = 5V, IN1 = IN2 = no connection, RISET = 63.4kΩ, RPU = 10kΩ at ERR, OUT1 and OUT2, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Notes 1, 2, and 4) PARAMETER IN1, IN2 Blanking Time at Hall Switch Power-Up IN1, IN2 Current Ramp Rate After Turn-On SYMBOL tBL tRAMP CONDITIONS IIH = -11.5mA to GND, time from VIN_ = 500mV until OUT_ high, CL = 20pF (Note 3) MIN TYP 50 MAX UNITS 140 µs VIN = GND 3.8 mA/µs Delay from IN_ to OUT_ (Filter Delay) tDEL From IIH to IIL or from IIL to IIH, CL = 20pF, Figure 1 6.5 µs Delay from IN_ Fault to ERR tERR From IIL to ISC or from IIH to IOC, falling edge only, CL = 20pF, Figure 1 31 ns Delay from DIAG High to OUT_ and ERR tDLH Rising edge of DIAG to falling or rising edge of outputs, CL = 20pF, Figure 1 350 ns Delay from DIAG Low to OUT_ and ERR tDHL Falling edge of DIAG to falling or rising edge of outputs, CL = 20pF, Figure 1 1.6 µs Delay Difference Between Rising and Falling Edges for Both Channels tDM CHALL-BYPASS = 0.01µF, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF 20 ns Delay Difference Between Channels tCC CHALL-BYPASS = 0.01µF, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF 100 ns Maximum Frequency on Hall Inputs fMAX CHALL-BYPASS = 0.01µF, IIH = -11.5mA and IIL = -7.2mA, CL = 20pF IN_ Pulse Length Rejected by Filter to OUT_ PR Figure 2 50 kHz 5.5 µs Note 1: All DC specifications are 100% tested at TA = +25°C. AC specifications and specifications over -40°C to +125°C 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 20µs 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 = 63.4kΩ. The parameters tRAMP and fMAX increase 8%, and tDEL and PR decrease 8% with RISET = 59.0kΩ. The limits for tBL and fMAX apply for both resistor values. _______________________________________________________________________________________ 3 MAX9921 DC ELECTRICAL CHARACTERISTICS (continued) Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921 Timing Diagrams APPROX. 50mA RETRY SHORT CIRCUIT 14mA IN 1 7mA 4mA/μs HALL SENSOR OPEN CIRCUIT 0mA tDEL 5V OUT1 0V 5V OUT2 0V tERR tERR 5V ERR 0V 5V DIAG 0V Figure 1. Timing Diagram 4 _______________________________________________________________________________________ Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics PR PR 14mA IN_ 7mA 0mA tDEL 5V tDEL OUT_ 0V Figure 2. Hall Input Pulse Rejection _______________________________________________________________________________________ 5 MAX9921 Timing Diagrams (continued) Typical Operating Characteristics (VBAT = 14V, TA = +25°C, unless otherwise noted.) 1.3 TA = +25°C 1.3 TA = +125°C 1.5 1.4 1.1 1.0 0.9 BAT CURRENT (mA) 1.2 BAT CURRENT (mA) 1.1 1.0 0.9 1.3 1.2 1.1 0.8 0.8 1.0 0.7 0.7 0.9 0.6 0.8 0.6 19.5 20.0 20.5 BAT VOLTAGE (V) 21.0 19.0 20.0 20.5 BAT VOLTAGE (V) 19.0 21.0 1.3 MAX9921 toc04 1.3 TA = -40°C 1.2 1.2 BAT CURRENT (mA) 1.1 TA = +25°C 1.0 0.9 HALL INPUTS DISABLED 20.0 20.5 BAT VOLTAGE (V) 1.1 TA = +125°C 1.4 1.0 0.9 0.8 1.2 1.0 OPERATING MODE 0.8 0.7 HALL INPUTS DISABLED OPERATING MODE 0.6 0.6 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 HALL INPUT CURRENT HYSTERESIS FOR HIGH/LOW THRESHOLDS vs. TEMPERATURE HALL INPUT CURRENT HYSTERESIS FOR HIGH/LOW THRESHOLD vs. VBAT TA = +125°C 35 TA = +25°C 30 25 20 15 TA= -40°C 10 9.6 9.4 HIGH THRESHOLD 9.2 9.0 LOW THRESHOLD 8.8 MAX9921 toc09 9.8 9.8 9.6 HALL INPUT CURRENT (mA) 40 HALL INPUT CURRENT (mA) 45 MAX9921 toc08 10.0 MAX9921 toc07 50 9.4 HIGH THRESHOLD 9.2 LOW THRESHOLD 9.0 8.8 8.6 5 0 8.6 8.4 0 6 21.0 1.6 HALL INPUTS DISABLED OPERATING MODE 0.7 19.5 BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE 0.8 19.5 BAT CURRENT (mA) 19.0 MAX9921 toc05 BAT CURRENT (mA) 1.2 1.6 MAX9921 toc06 TA = -40°C MAX9921 toc02 1.4 MAX9921 toc01 1.4 BAT CURRENT (mA) BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE MAX9921 toc03 BAT SUPPLY CURRENT vs. VBAT IN OPERATING MODE BAT CURRENT (nA) MAX9921 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics 10 20 30 BAT VOLTAGE (V) 40 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 6 8 10 12 14 BAT VOLTAGE (V) _______________________________________________________________________________________ 16 18 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics 85 80 75 70 65 60 MAX9921 toc11 3 9 2 8 7 6 1 5 0 -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) DELAY FROM IN_ FAULT TO ERR (FILTER DELAY) vs. TEMPERATURE DELAY DIFFERENCE BETWEEN RISING AND FALLING EDGES FOR BOTH CHANNELS vs. TEMPERATURE DELAY DIFFERENCE BETWEEN CHANNELS vs. TEMPERATURE 160 30 20 140 120 200 DELAY DIFFERENCE (ns) DELAY DIFFERENCE (ns) 40 250 IN1 AND IN2 100 80 60 40 10 MAX9921 toc15 180 MAX9921 toc13 50 DELAY (μs) 4 DELAY (μs) 90 10 MAX9921 toc14 IN_ BLANKING TIME (μs) 95 5 IN_ CURRENT RAMP RATE (mA/μs) MAX9921 toc10 100 DELAY FROM IN_ TO OUT_ (FILTER DELAY) vs. TEMPERATURE IN_ CURRENT RAMP RATE AFTER TURN-ON vs. TEMPERATURE MAX9921 toc12 IN_ BLANKING TIME AT HALL SWITCH POWER-UP vs. TEMPERATURE 150 100 50 20 0 -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) MAXIMUM FREQUENCY ON HALL INPUTS vs. TEMPERATURE IN_ PULSE LENGTH REJECTED BY FILTER TO OUT_ vs. TEMPERATURE VBAT UNDERVOLTAGE THRESHOLD vs. TEMPERATURE 80 75 70 IN1 AND IN2, 50% DUTY CYCLE 5 4 IN1 AND IN2 WITH POSITIVE PULSE IN1 AND IN2 WITH NEGATIVE PULSE 3 2 60 MAX9921 toc18 6 6.1 6.0 VBAT THRESHOLD (V) 85 6.2 MAX9921 toc17 90 PULSE LENGTH (μs) 95 FREQUENCY (kHz) 7 MAX9921 toc16 100 65 0 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 5.9 VBAT RISING, ERR GOES HIGH 5.8 5.7 5.6 5.5 VBAT FALLING, ERR GOES LOW 5.4 1 55 50 5.3 5.2 0 -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) _______________________________________________________________________________________ 7 MAX9921 Typical Operating Characteristics (continued) (VBAT = 14V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VBAT = 14V, TA = +25°C, unless otherwise noted.) VBAT OVERVOLTAGE THRESHOLD vs. TEMPERATURE 20.3 70 20.2 20.1 VBAT FALLING, ERR GOES LOW 20.0 19.9 19.8 19.7 MAX9921 toc20 80 INPUT PULLUP RESISTANCE (Ω) 20.4 VBAT THRESHOLD (V) INPUT PULLUP RESISTANCE vs. VBAT MAX9921 toc19 20.5 VBAT RISING, ERR GOES HIGH 60 TA = +25°C TA = +125°C 50 40 30 TA = -40°C 20 10 19.6 0 19.5 6 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 9 12 VBAT (V) 15 18 RESPONSE OF INPUT TO SHORT TO GROUND THRESHOLD CURRENT vs. ISET RESISTOR INPUT CURRENT FOR OUTPUT HIGH AND INPUT CURRENT FOR OUTPUT LOW 10 MAX9921 toc21 MAX9921 toc22 15 CHANGE IN THRESHOLD CURRENT (%) MAX9921 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics VIN1 10V/div 0V 5 VERR 5V/div 0V HYSTERESIS 0 -5 IIN1 25mA/div 0A -10 -15 -15 -10 -5 0 5 10 CHANGE IN ISET RESISTOR (%) 15 10μs/div STARTUP OF HALL INPUT FROM SHUTDOWN MAX9921 toc23 VIN_ 10V/div BLANKING PERIOD VOUT_ 5V/div VOE_ IIN_ 5V/div 10mA/div 20μs/div 8 _______________________________________________________________________________________ Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics PIN NAME FUNCTION 1 BAT Battery Power Supply. Connect BAT to the positive supply through an external reverse-polarity diode. Bypass BAT to ground with a 0.1µF capacitor. 2 ISET Current-Setting Input. Connect a 63.4kΩ, 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. 3 IN1 4 IN2 5 GND Ground 6 OUT2 Open-Drain Output Signal 2. OUT2 is the signal translated from Hall Sensor 2. Connect a 10kΩ or larger pullup resistor to logic supply. 7 OUT1 Open-Drain Output Signal 1. OUT1 is the signal translated from Hall Sensor 1. Connect a 10kΩ or larger pullup resistor to logic supply. 8 9 10 Hall-Effect Sensor Input 1. Bypass IN1 to BAT or GND with a 0.01µF capacitor. Terminate an unused input with a 1.5kΩ resistor from IN1 to GND to prevent false error diagnostics. Hall-Effect Sensor Input 2. Bypass IN2 to BAT or GND with a 0.01µF capacitor. Terminate an unused input with a 1.5kΩ resistor from IN2 to GND to prevent false error diagnostics. ERR Open-Drain Diagnostic and Error Output. Connect a 10kΩ 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. OE Output Enable Input. OE has an internal 80kΩ 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 40µs, 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. DIAG Diagnostic Enable Input. DIAG has an internal 80kΩ 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 40µs, 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. _______________________________________________________________________________________ 9 MAX9921 Pin Description MAX9921 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics Functional Diagram 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. BAT DIAG ISET REF GENERATION, DIAGNOSTICS, AND OVERVOLTAGE DETECT ERR CONTROL OE MAX9921 IN1 FILTER OUT1 IN2 FILTER Hall Input Diagnostic OUT2 GND Detailed Description The MAX9921 connects two 2-wire Hall-effect sensors to a low-voltage µP. 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. 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 50µA. 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. Hall Input Fault Detection If a fault is detected, the ERR output is asserted low to notify the µP. 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 OUTPUT DIAG ERR OUT1 OUT2 0 1 0 or 1 0 or 1 10 DIAGNOSIS COMMENT OUT1 and OUT2 indicate state of IN1 and IN2, respectively Normal mode: No fault indication (outputs indicate Hall sensor high or low status) Fault on IN1 and/or IN2, or VBAT out of range, or power-up or restart blanking (unknown current level of IN1 and IN2) Normal mode: ERR asserted low indicates fault (outputs may no longer indicate the high or low state of the Hall sensors) 0 0 0 0 0 0 0 0 or 1 Fault on IN1 or restart blanking of IN1 Normal mode: ERR asserted low indicates fault; Hall output 2 continues signaling 0 0 0 or 1 0 Fault on IN2 or restart blanking of IN2 Normal mode: ERR asserted low indicates fault; Hall output 1 continues signaling ______________________________________________________________________________________ Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics INPUT OUTPUT ERR DIAG OUT1 MAX9921 Table 2. Diagnostic Truth Table (Diagnostic Mode) DIAGNOSIS OUT2 1 0 0 0 No fault 1 0 0 1 IN1 open circuit, or IN1 open circuit and fault on IN2 1 0 1 0 IN1 shorted to battery, or IN1 shorted to battery and fault on IN2 1 0 1 1 IN1 shorted to ground, or IN1 shorted to ground and fault on IN2 1 1 0 0 VBAT out of range, or power-up or restart and blanking cycle (dominant fault masks all other faults) 1 1 0 1 IN2 open circuit 1 1 1 0 IN2 shorted to battery 1 1 1 1 IN2 shorted to ground 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 REVERSE-POLARITY DIODE FOR OTHER CIRCUITRY RISET BAT MAX9921 MAX9921 BAT DIAG BAT DIAG ISET OE ISET OE IN1 ERR IN1 ERR IN2 OUT1 IN2 OUT1 GND OUT2 GND OUT2 OTHER CIRCUITRY GND Figure 3. Several MAX9921s Connected to a Common Reverse-Polarity Diode ______________________________________________________________________________________ 11 MAX9921 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 50µA 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 0.02µF 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. 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 50µA 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 VIN_ HALL INPUT OPEN-CIRCUIT FAULT INDICATED VBAT - 25mV 5mV/ms HALL INPUT DISCONNECTED FROM SENSOR 0V TIME IIN_ 50µA 0A TIME Figure 4. Hall Input Ramps to Open-Circuit Fault When Short to Ground is Relieved 12 ______________________________________________________________________________________ Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics MAX9921 14V VBAT - 500mV VIN_ 8V HALL INPUT RECONNECTED TO HALL SENSOR 0V TIME 11.5mA IIN_ 4mA/µs 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 CRITERION ERR OUTPUT HALL INPUT RESPONSE VBAT < 6V — Asserted low Shutoff current to both Hall sensors Both IN1 and IN2 are restarted with blanking cycle when VBAT returns to proper range. VBAT > 18V — Asserted low Shutoff current to both Hall sensors Both IN1 and IN2 are restarted with blanking cycle when VBAT returns to proper range. IIN < 2mA Asserted low Shutoff current to corresponding Hall sensor When a Hall input is again loaded, terminating open input condition, the Hall input are restarted with blanking cycle. Shutoff current to corresponding Hall sensor 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. Shutoff current to corresponding Hall sensor. 50µA of pullup current is sourced to IN1 or IN2 to aid in troubleshooting. 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 Hall input shorted to battery Hall input shorted to ground VIN > VBAT due to external reverse-battery Asserted low protection diode IIN > 23mA Asserted low COMMENT/RECOVERY ______________________________________________________________________________________ 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 Hall Input Bypass Capacitor MAX9921 x_ VCC IN_ GND The MAX9921 is optimized for use with external protection 0.01µF 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. 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 50Ω (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 MANUFACTURER WEBSITE COMMENT HAL573-6 Micronas www.micronas.com 2-wire HAL556/560/566 Micronas www.micronas.com 2-wire HAL581/584 Micronas www.micronas.com 2-wire A1140/1/2/3 Allegro www.allegromicro.com 2-wire A1180/81/82/83 Allegro www.allegromicro.com 2-wire Note: The Hall switches listed above are supported by the MAX9921 using RISET = 63.4kΩ. 14 ______________________________________________________________________________________ Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics Chip Information PROCESS: BiCMOS TOP VIEW BAT 1 ISET 2 IN1 3 IN2 GND Package Information 10 DIAG 9 OE 8 ERR 4 7 OUT1 5 6 OUT2 MAX9921 µMAX 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 PACKAGE CODE DOCUMENT NO. 10 µMAX U10+2 21-0061 ______________________________________________________________________________________ 15 MAX9921 Pin Configuration MAX9921 Dual, 2-Wire Hall-Effect Sensor Interface with Diagnostics Revision History REVISION NUMBER REVISION DATE 0 6/08 Initial release 1 1/10 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 © 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.