Rainbow Electronics MAX9921 - Manual (Page 9)

MAX9921
Dual, 2-Wire Hall-Effect Sensor Interface
with Diagnostics
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Pin Description
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 63.4k Ω, 1% resistor (R
ISET ) 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
Hall-Effect Sensor Input 1. Bypass IN1 to BAT or GND with a 0.01µF capacitor. Terminate an unused input with a
1.5k
Ω resistor from IN1 to GND to prevent false error diagnostics.
4 IN2
Hall-Effect Sensor Input 2. Bypass IN2 to BAT or GND with a 0.01µF capacitor. Terminate an unused input with a
1.5k
Ω resistor from IN2 to GND to prevent false error diagnostics.
5 GND Ground
6 OUT2
Open-Drain Output Signal 2. OUT2 is the signal translated from Hall Sensor 2. Connect a 10k Ω 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 10k Ω or larger pullup
resistor to logic supply.
8 ERR
Open-Drain Diagnostic and Error Output. Connect a 10k Ω 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.
9 OE
Output Enable Input. OE has an internal 80k Ω 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.
10 DIAG
Diagnostic Enable Input. DIAG has an internal 80k Ω 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-to-
low 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.