[AK09915]
9.4.3.6. Magnetic Sensor Overflow
AK09915 has the limitation for measurement range that the sum of absolute values of each axis should be
smaller than 4912 μT. (Note 12)
|X|+|Y|+|Z| < 4912 μT
When the magnetic field exceeded this limitation, data stored at measurement data are not correct. This is
called Magnetic Sensor Overflow.
When magnetic sensor overflow occurs, HOFL bit turns to “1”. When measurement data register (HXL to
HZH) is updated, HOFL bit is updated.
(Note 12) BSE: 0.15 μT/LSB
9.4.4. Self-test Mode
Self-test mode is used to check if the magnetic sensor is working normally.
When Self-test mode (MODE[4:0] bits = “10000”) is set, magnetic field is generated by the internal magnetic
source and magnetic sensor is measured. Measurement data is stored to measurement data registers (HXL to
HZH), then AK09915 transits to Power-down mode automatically.
Data read sequence and functions of read-only registers in Self-test mode is the same as Single measurement
mode.
9.4.4.1. Self-test Sequence
(1)Set Power-down mode. (MODE[4:0] bits = “00000”)
(2)Set Self-test mode. (MODE[4:0] bits = “10000”)
(3)Check Data Ready or not by any of the following method.
Polling DRDY bit of ST1 register
Monitor DRDY pin
When Data Ready, proceed to the next step.
(4)Read measurement data (HXL to HZH)
9.4.4.2. Self-test Judgment
When measurement data read by the above sequence is in the range of following table, AK09915 is working
normally.
HX[15:0] bits
HY[15:0] bits
HZ[15:0] bits
Criteria
-200 ≤HX≤ +200
-200 ≤HY≤ +200
-800 ≤HZ≤ -200
9.5. Noise Suppression Filter (NSF)
In Single measurement mode, Continuous measurement modes (1 to 6), output from the magnetic sensor can
be filtered to suppress the noise. This filter name is Noise Suppression Filter (NSF). When NSF bit = “0”, NSF
is “disable” and output magnetic data is not filtered. When NSF bit = “1”, output magnetic data is filtered.
NSF bit can be changed in Power-down mode only. Default NSF bit is “disable” (NSF bit = “0”).
9.6. Sensor Drive Select
AK09915 can choose “Low power” or “Low noise” drive.
“Low power” is used to save the current consumption and “Low noise” is used to reduce the noise of the
AK09915. When Low power (SDR bit = “0”) is set, average current consumption at 100 Hz repetition rate is
reduced from 1.8 mA to 0.9 mA. When Low noise (SDR bit = “1”) is set, output magnetic data noise is less
than Low power (about 70% of Low power).
SDR bit can be changed in Power-down mode only. Default SDR bit is Low power enable (SDR bit = “0”).
015006484-E-02
2016/7
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AKM [ ASAHI KASEI MICROSYSTEMS ]
