HAL575SF-K datasheet(7/36 Pages) MICRONAS

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DATA SHEET

HAL57x, HAL58x

Micronas

Dec. 22, 2008; DSH000145_003EN

2. Functional Description

The HAL 57x, HAL58x two-wire sensors are monolithic

integrated circuits which switch in response to mag-

netic fields. If a magnetic field with flux lines perpendic-

ular 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 tempera-

tures.

If the magnetic field exceeds the threshold levels, the

current source switches to the corresponding state. In

the low current consumption state, the current source

is switched off and the current consumption is caused

only by the current through the Hall sensor. In the high

current consumption state, the current source is

switched on and the current consumption is caused by

the current through the Hall sensor and the current

source. The built-in hysteresis eliminates oscillation

and provides switching behavior of the output signal

without bouncing.

Magnetic offset caused by mechanical stress is com-

pensated for by using the “switching offset compensa-

tion technique”. An internal oscillator provides a two-

phase clock. In each phase, the current is forced

through the Hall plate in a different direction, and the

Hall voltage is measured. At the end of the two

phases, the Hall voltages are averaged and thereby

the offset voltages are eliminated. The average value

is compared with the fixed switching points. Subse-

quently, the current consumption switches to the corre-

sponding state. The amount of time elapsed from

crossing the magnetic switching level to switching of

the current level can vary between zero and 1/fosc.

Shunt protection devices clamp voltage peaks at the

VDD-pin together with external series resistors.

Reverse current is limited at the VDD-pin by an inter-

nal series resistor up to

−15 V. No external protection

diode is needed for reverse voltages ranging from 0 V

−15 V.

Fig. 2–1: HAL57x, HAL58x block diagram

Fig. 2–2: Timing diagram (example: HAL581)

Temperature

Dependent

Bias

Switch

Hysteresis

Control

Comparator

Current

Source

VDD

Clock

Hall Plate

GND

2, x

HAL 57x, HAL58x

Reverse

Voltage &

Overvoltage

Protection

x = pin 3 for TO92UA-1/-2 package

x = pin 4 for SOT89B-1 package

1/fosc =

μs

B OFF

B ON

IDDhigh

IDDlow

IDD

fosc

6.9

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