HAL54x
2. Functional Description
The Hall effect sensor is a monolithic integrated circuit
that switches in response to magnetic fields. If a mag-
netic 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 induc-
tion of magnets at higher temperatures. If the magnetic
field exceeds the threshold levels, the open drain out-
put switches to the appropriate state. The built-in hys-
teresis eliminates oscillation and provides switching
behavior of output without bouncing.
Magnetic offset caused by mechanical stress is com-
pensated for by using the “switching offset compensa-
tion technique”. Therefore, an internal oscillator pro-
vides 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 mag-
netic switching level to switching of output can vary
between zero and 1/f
osc
.
Shunt protection devices clamp voltage peaks at the
Output-pin and 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
reverse protection diode is needed at the V
DD
pin for
reverse voltages ranging from 0 V to
−15
V.
A built-in reset-circuit clamps the output to the “high”
state (reset state) during power-on or when the supply
voltage drops below a reset voltage of V
reset
< 4.3 V.
For supply voltages between V
reset
and 4.3 V, the out-
put state of the device responds to the magnetic field.
For supply voltages above 4.3 V, the device works
according to the specified characteristics.
V
DD
1
Reverse
Voltage &
Overvoltage
Protection
Temperature
Dependent
Bias
DATA SHEET
HAL54x
Hysteresis
Control
Power-on &
Undervoltage
Reset
Short Circuit &
Overvoltage
Protection
Hall Plate
Switch
Comparator
Output
OUT
3
Clock
GND
2
Fig. 2–1:
HAL54x block diagram
f
osc
t
B
B
ON
t
V
OUT
V
OH
V
OL
t
I
DD
1/f
osc
= 9
μs
t
f
t
Fig. 2–2:
Timing diagram
6
Feb. 12, 2009; DSH000023_003EN
Micronas
MICRONAS [ MICRONAS ]
