MAX9921 is a hall-effect sensor interface with diagnostic and protection features that interfaces two 2-wire hall-effect sensors to a low-voltage micro-processor (µP). The 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 features that 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.
The MAX9921 provides a single‑chip solution for interfacing two 2‑wire Hall‑effect sensors to a low‑voltage microprocessor. It supplies and monitors sensor current, filters the sensed level, and outputs corresponding open‑drain logic signals with diagnostic capabilities.
The device operates from 6 V to 18 V, works over an automotive temperature range of –40 °C to +125 °C, and protects Hall sensors from transients up to 60 V. Features include current ramping at 4 mA/µs, output enable multiplexing, and fault detection for open, short‑to‑battery, or short‑to‑ground conditions.
| Operating supply voltage range | 6 V to 18 V |
|---|---|
| Automotive temperature range | -40 °C to +125 °C |
| Package type | 10‑pin µMAX |
| Open‑drain output voltage compatibility | up to 5.5 V |
| Current ramp rate to Hall sensors | 4 mA/µs |
| Shutdown mode supply current | 1 µA |
The MAX9921 operates from 6 V to 18 V supply voltage.
It shuts off current to the sensors when the battery voltage is outside the 6 V‑18 V range and isolates them from transients up to 60 V.
The device provides an 80 µs blanking time after power‑up, with an additional 20 µs in shutdown mode.
Yes, the Output Enable (OE) input allows multiplexing of outputs from multiple MAX9921s.