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Philips Semiconductors
Electronic Compass Design using
KMZ51 and KMZ52
coils can be arranged much closer to the sensor element, they require significantly less current to generate the
required field strengths. This reduces expenditure and thus cost at the signal conditioning unit side.
In the signal conditioning section, the techniques of flipping and compensation are described in detail.
4.3 Philips MR Sensors for Compass Systems
Philips Semiconductors offers at present two sensor products, dedicated to this application field. Both products
employ the previously described barber pole structure with its inherent linearity and high sensitivity.
The primary device is the KMZ52, which comprises all elements of a compass sensor system within one
package, i.e. two weak field sensors with 90° displacement, each having a set/reset and a compensation coil
(ref. to figure 3). The KMZ51 is a single sensor with set/reset and compensation coils. This can be employed
together with a KMZ52 to form a three-dimensional sensor, in order to compensate for tilt, as will be described
in section 9. Figure 9 shows a simplified circuit diagram of the KMZ51, showing the MR resistor bridge as well
as the set/reset and compensation coils. Table 1 provides an overview on Philips´ compass sensor portfolio.
1- or 2-dimensional sensor
Package
recommended supply voltage
typ. sensitivity
offset voltage
Applicable field range
Integrated set/reset coils for
flipping
Integrated compensation coils
1
Thus, the sensor delivers 16mV per V supply voltage and per kA/m field strength.
Thus, the maximum offset voltage is ± 1.5mV per V supply voltage.
2
−IF
handbook, halfpage
8
set/reset
coil
1
+IF
Figure 9
Simplified circuit diagram of KMZ 51
Table 1
Philips MR sensors for compass applications
+VO
−VO
−IC
7
6
2
3
+IC
VCC
GND
KMZ51
KMZ52
1-dim.
2-dim.
SO 8
SO 16
5
5
16
16
-1.5 ... 1.5
-1.5 ... 1.5
-0.2 ... 0.2
-0.2 ... 0.2
yes
yes
yes
yes
15
Application Note
5
compen-
sation
coil
4
MGD793
UNIT
-
-
V
(mV/V) / (kA/m)
mV/V
kA/m
-
-
AN00022
1
2
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