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.
Key Features
Applications/Uses
Withstands 60V at BAT Supply and Hall Inputs
6V to 18V Operating Voltage Range
Provides Supply Current and Interfaces to Two 2-Wire Hall Sensors
Error Output with Diagnostics of Hall Inputs and BAT Voltage
Protects Hall Sensors from Overvoltage by Isolating them from Supply Transients
Hall Inputs Protected from Short to Ground
Ramps Current to Hall Sensors at 4mA/µs
Output Enable Input Allows Multiplexing of Outputs from Multiple MAX9921s
Hall Output Filtering
Hall Sensor Blanking Following Hall Sensor Power-Up and Restart
Low-Power Shutdown, Controlled with OE and DIAG Inputs
Operates with ±2V Ground Shifts Between Hall Sensor and MAX9921
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