High-sensitivity Hall effect latch enhances position sensing in automotive motor control systems

Diodes Incorporated expands its AH371xQ series of automotive-compliant* Hall effect latches for motor control applications that need to operate at very low magnetic thresholds and bipolar switching behaviors. Featuring a proprietary Hall plate design, the AH3711Q is used for brushless DC (BLDC) motor control, valve operation, linear and incremental rotary encoders, and position-sensing functions. Vehicle applications include window power-lift and sunroof movement, tailgate opening/closing mechanisms, seat adjustment motors, cooling fans, water/oil pumps, and speed measurement.

The magnetic operate (B_OP) and release (B_RP) points over the AH3711Q, which covers ±10 Gauss, delivers greater placement flexibility. This ultra-high sensitivity enables it to detect weaker magnetic fields, allowing the use of smaller, more cost-effective magnets to reduce system size and the total bill-of-materials (BOM) cost. The greater magnetic margin also enables aggressive duty-cycle reduction, lowering power consumption and extending battery life.

To enhance system reliability, the Hall effect latch operates over a 3V to 27V range. The device has a reverse blocking diode with a Zener clamp on the supply, and the output has an overcurrent limit and a Zener clamp. This combination of components provides protection against 40V load dumps, reverse polarity, and short circuits. The wide input voltage range, coupled with a high 8kV HBM and 1kV CDM ESD rating, further enhances the device’s robustness in harsh environments.

The device also features a chopper-stabilized design, which minimises switch-point drift across the full -40°C to +150°C temperature range and provides high resistance to physical stress during PCB assembly. This mitigates the effects of thermal variation and enhances stray-field immunity. The power-on time is typically 13µs, which helps avoid system-level faults. Open-drain outputs offer greater external pull-up flexibility for voltages above or below the supply voltage.

The magnetic operating and release polarity is opposite for the SOT23 (Type S) and SC59 packages. For operation, the SOT23 (Type S) and SIP-3 (Bulk Pack) packages require the south pole to the part-marking side, and the SC59 requires the south pole to the non-part-marking side.