HAL55x, HAL56x
2. Functional Description
HAL55x, HAL56x
The HAL55x, HAL56x two-wire sensors are monolithic
integrated circuits which switch 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.
Reverse
V
Temperature
Hysteresis
Dependent
Control
DD
1
Voltage &
Overvoltage
Protection
Bias
Hall Plate
Comparator
Current
Switch
Source
Clock
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
bythecurrentthroughtheHallsensor. Inthehighcurrent
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 bounc-
ing.
GND
2
Fig. 2–1: HAL55x, HAL56x block diagram
f
osc
Magnetic offset caused by mechanical stress is com-
pensated for by using the “switching offset compensa-
tion technique”. An internal oscillator provides a two-
phaseclock. Ineachphase, thecurrentisforcedthrough
the Hall plate in a different direction, and the Hall voltage
is measured. At the end of the two phases, the Hall volt-
ages are averaged and thereby the offset voltages are
eliminated. The average value is compared with the
fixed switching points. Subsequently, the current con-
sumption switches to the corresponding state. The
amount of time elapsed from crossing the magnetic
switching level to switching of the current level can vary
t
t
t
t
B
B
B
OFF
ON
I
DD
I
DDhigh
I
DDlow
between zero and 1/f
.
osc
I
DD
Shunt protection devices clamp voltage peaks at the
-pin together with external series resistors. Reverse
V
DD
current is limited at the V -pin by an internal series
DD
1/f
osc
= 6.9 µs
resistor up to –15 V. No external protection diode is
needed for reverse voltages ranging from 0 V to –15 V.
Fig. 2–2: Timing diagram (example: HAL56x)
Micronas
5
MICRONAS [ MICRONAS ]
