HAL556_1 Datasheet, PDF (6/26 Pages) Micronas – Two-Wire Hall-Effect Sensor Family

HAL55x, HAL56x
DATA SHEET
2. Functional Description
The HAL55x, HAL56x 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/f_osc.
Shunt protection devices clamp voltage peaks at the
V_DD-pin together with external series resistors.
Reverse current is limited at the V_DD-pin by an internal
series resistor up to −15 V. No external protection
diode is needed for reverse voltages ranging from 0 V
to −15 V.
HAL55x, HAL56x
V_DD
Reverse
Voltage &
1
Overvoltage
Protection
Hall Plate
Temperature
Dependent
Bias
Hysteresis
Control
Switch
Comparator
Current
Source
GND
2
Clock
Fig. 2–1: HAL55x, HAL56x block diagram
f_osc
t
B
B_OFF
B_ON
t
I_DD
I_DDhigh
I_DDlow
t
I_DD
1/f_osc = 6.9 μs
t
Fig. 2–2: Timing diagram (example HAL56x)
6
Aug. 11, 2009; DSH000026_004EN
Micronas