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Fabricante

HAL740SF-E

Dual Hall-Effect Sensors with Independent Outputs

Micronas 

HAL700, HAL740

DATA SHEET

2. Functional Description

The HAL700 and the HAL740 are monolithic inte-

grated circuits with two independent subblocks each

consisting of a Hall plate and the corresponding com-

parator. Each subblock independently switches the

comparator output in response to the magnetic field at

the location of the corresponding sensitive area. If a

magnetic field with flux lines perpendicular to the sen-

sitive area is present, the biased Hall plate generates a

Hall voltage proportional to this field. The Hall voltage

is compared with the actual threshold level in the com-

parator. The subblocks are designed to have closely

matched switching points. The output of comparator 1

attached to S1 controls the open drain output at Pin 3.

Pin 2 is set according to the state of comparator 2 con-

nected to S2.

The temperature-dependent bias – common to both

subblocks – increases the supply voltage of the Hall

plates and adjusts the switching points to the decreas-

ing induction of magnets at higher temperatures. If the

magnetic field exceeds the threshold levels, the com-

parator switches to the appropriate state. The built-in

hysteresis prevents oscillations of the outputs.

The magnetic offset caused by mechanical stress is

compensated for by use of “switching offset compen-

sation techniques”. Therefore, an internal oscillator

provides a two-phase clock to both subblocks. For

each subblock, 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.

Shunt protection devices clamp voltage peaks at the

output pins 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.

Fig. 2–2 and Fig. 2–3 on page 7 show how the output

signals are generated by the HAL700 and the

HAL740. The magnetic flux density at the locations of

the two Hall plates is shown by the two sinusodial

curves at the top of each diagram. The magnetic

switching points are depicted as dashed lines for each

Hall plate separately.

Clock

t

BS1

BS1on

t

BS2

BS2on

t

Pin 2

VOH

VOL

t

Pin 3

VOH

VOL

t

IDD

1/fosc

tf

t

tf

Fig. 2–1: HAL700 timing diagram with respect to the

clock phase

6

Nov. 30, 2009; DSH000029_002EN

Micronas

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