Note: The HAL 3xy sensor family is not recommended for new designs.
The HAL 300 and the HAL 320 are differential Hall switches produced in CMOS technology. The sensors include two temperature-compensated Hall plates with active offset compensation, a differential amplifier with a Schmitt trigger, and an open-drain output transistor .
These differential sensors respond to spatial differences of the magnetic field. The Hall voltages at the two Hall plates, S1 and S2, are amplified with a differential amplifier . The differential signal is compared with the actual switching level of the internal Schmitt trigger . Accordingly, the output transistor is switched on or off . The differential signal can be derived via a rotating multi-pole-ring in front of the branded side of the package (HAL 300) or via a magnet on the back side of the package generating a back-bias field at both Hall plates (HAL 320) .
The active offset compensation leads to constant magnetic characteristics over supply voltage and temperature. The sensors are designed for automotive and industrial applications and operate with supply voltages from 4.5 to 24 V in the junction temperature range –40 °C up to 170 °C .
The sensors are available in the SMD package SOT89B and in the leaded version TO92UA.
Block diagram – system architecture
This Hall effect sensor is a monolithic integrated circuit with 2 Hall plates 2.25 mm apart that switches in response to differential magnetic fields. If magnetic fields with flux lines perpendicular to the sensitive areas are applied to the sensor, the biased Hall plates force Hall voltages proportional to these fields. The difference of the Hall voltages is compared with the actual threshold level in the comparator. The temperature-dependent bias increases the supply voltage of the Hall plates and adjusts the switching points to the decreasing induction of magnets at higher temperatures. If the differential magnetic field exceeds the threshold levels, the open drain output switches to the appropriate state. The builtin hysteresis eliminates oscillation and provides switching behavior of the output without oscillation.