HAL401
DATA SHEET
2. Functional Description
External filtering or integrating measurement can be
done to eliminate the AC component of the signal. Re-
sultingly, the influence of mechanical stress and temper-
ature cycling is suppressed. No adjustment of magnetic
offset is needed.
GND
4
Chopper
Oscillator
The sensitivity is stabilized over a wide range of temper-
ature and supply voltage due to internal voltage regula-
tion and circuits for temperature compensation.
Temp.
Dependent
Bias
Offset
Compensation;
Hallplate
Switching
Matrix
Offset Compensation (see Fig. 2–2)
The Hall Offset Voltage is the residual voltage measured
in absence of a magnetic field (zero-field residual volt-
age). This voltage is caused by mechanical stress and
can be modeled by a displacement of the connections
for voltage measurement and/or current supply.
Protection
Device
V
OUT1
2
OUT2
3
DD
1
Compensation of this kind of offset is done by cyclic
commutating the connections for current flow and volt-
age measurement.
Fig. 2–1: Block diagram of the HAL401 (top view)
– First cycle:
The Linear Hall Sensor measures constant and low fre-
quency magnetic flux densities accurately. The differen-
The hall supply current flows between points 4 and 2.
In the absence of a magnetic field, V is the Hall Off-
set Voltage (+V ). In case of a magnetic field, V is
the sum of the Hall voltage (V ) and V
13
tial output voltage V
(difference of the voltages on
OUTDIF
Offs
13
pin2andpin3)isproportionaltothemagneticfluxdensi-
ty passing vertically through the sensitive area of the
.
H
Offs
V
13
= V + V
H Offs
chip. The common mode voltage V
(average of the
CM
– Second cycle:
The hall supply current flows between points 1 and 3.
voltages on pin 2 and pin 3) of the differential output am-
plifier is a constant 2.2 V.
In the absence of a magnetic field, V is the Hall Off-
24
set Voltage with negative polarity (–V ). In case of
The differential output voltage consists of two compo-
nents due to the switching offset compensation tech-
nique. The average of the differential output voltage rep-
resents the magnetic flux density. This component is
overlaid by a differential AC signal at a typical frequency
of 147 kHz. The AC signal represents the internal offset
voltages of amplifiers and hall plates that are influenced
by mechanical stress and temperature cycling.
Offs
a magnetic field, V is the difference of the Hall volt-
24
age (V ) and V
.
H
Offs
= V – V
H Offs
V
24
In the first cycle, the output shows the sum of the Hall
voltage and the offset; in the second, the difference of
both. The difference of the mean values of V
and
OUT1
V
(V
) is equivalent to V
.
OUT2
OUTDIF
Hall
V
for Bu0 mT
V
OUT1
Note: The numbers do not
represent pin numbers.
I
C
1
V
OUTDIF/2
V
CM
2
1
V
V
Offs
OUTDIF
4
V
V
OUTAC
OUTDIF/2
V
Offs
I
C
2
3
4
V
OUT2
1/f = 6.7 μs
CH
3
V
V
t
a) Offset Voltage
Fig. 2–2: Hall Offset Compensation
b) Switched Current Supply
c) Output Voltage
6
Micronas
MICRONAS [ MICRONAS ]
