The Hall switches HAL 525* and HAL 526 are produced in CMOS technology. These sensors include a temperature-compensated Hall plate with active offset compensation, a comparator, and an open-drain output transistor. The comparator compares the actual magnetic flux through the Hall plate (Hall voltage) with the fixed reference values (switching points). Accordingly, the output transistor is switched on or off.

The active offset compensation leads to magnetic parameters which are robust against mechanical stress effects. In addition, the magnetic characteristics are constant in the full supply voltage and temperature range.

This sensor is designed for industrial and automotive applications and operates with supply voltages from 3.8 V to 24 V in the ambient temperature range from −40 °C up to 125 °C.

The HAL 525* and HAL 526 are available in the SMD package SOT89B-1 and in the leaded versions TO92UA-1 and TO92UA-2.

*Note: HAL 525 is not available for new designs. Please use HAL 526 instead.

System Architecture

The Hall effect sensor is a monolithic integrated circuit that switches in response to magnetic fields. If a magnetic field with flux lines perpendicular to the sensitive area is applied to the sensor, the biased Hall plate forces a Hall voltage proportional to this field. The Hall voltage 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 magnetic field exceeds the threshold levels, the open drain output switches to the appropriate state. The built-in hysteresis eliminates oscillation and provides switching behavior of output without bouncing.

Magnetic offset caused by mechanical stress is compensated for by using the “switching offset compensation technique”. Therefore, an internal oscillator provides a two phase clock. The Hall voltage is sampled at the end of the first phase. At the end of the second phase, both sampled and actual Hall voltages are averaged and compared with the actual switching point. Subsequently, the open drain output switches to the appropriate state. The time from crossing the magnetic switching level to switching of output can vary between zero and 1/fosc.

Shunt protection devices clamp voltage peaks at the Output-pin and VDD-pin together with external series resistors. Reverse current is limited at the VDD-pin by an internal series resistor up to -15 V. No external reverse protection diode is needed at the VDD-pin for reverse voltages ranging from 0 V to -15 V.

Block diagram of the HAL 525/526

Main Features

Available Types and Behavior

	Type	Switching Behavior		Typical Temperature Coefficient
	525*	latching		−2000 ppm/K
	526	latching		−2000 ppm/K
	*Note: HAL 525 is not available for new designs. Please use HAL 526 instead.