HAL710_1 Datasheet, PDF (6/19 Pages) Micronas – Hall-Effect Sensors with Direction Detection

HAL 710, HAL 730
DATA SHEET
2. Functional Description
The HAL 710 and the HAL 730 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 output of comparator 1 (connected to S1) directly
controls the Count Output. The outputs of both com-
parators enter the Direction Detection Block controlling
the state of the Direction Output. The Direction Output
is updated at every edge of comparator 1 (rising and
falling). The previous state of the Direction Output is
maintained between two edges of the Count Output
and in case the edges at comparator 1 and
comparator 2 occur in the same clock period. The sub-
blocks are designed to have closely matched switching
points.
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.
In order to achieve good matching of the switching
points of both subblocks, the magnetic offset caused
by mechanical stress is compensated for by use of
switching offset compensation 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 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.
Clock
t
B_S1
B_S1on
B_S2
t
B_S2on
Count
Output
V_OH
V_OL
Direction
t
Output
V_OH
V_OL
t
I_dd
1/f_osc
t_f t
Fig. 2–1: HAL 710 timing diagram with respect to the
clock phase
Fig. 2–2 and Fig. 2–3 on page 7 show how the output
signals are generated by the HAL 710 and the
HAL 730. 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.
At the time t = 0, the signal S2 precedes the signal S1.
The Direction Output is in the correct state according
to the definition of the sensor type.
When the phase of the magnetic signal changes its
sign, the Direction-Output switches its state with the
next signal edge of the Count Output.
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Oct. 13, 2009; DSH000031_002EN
Micronas