AK8998 Datasheet, PDF (31/59 Pages) Asahi Kasei Microsystems – Preliminary

[AK8998/W/D]
9. Output Reference Voltage Adjustment
Adjust the output reference voltage. The output reference voltage is adjusted by using the output
reference voltage adjustment EEPROM (address: 0A, 0Bh data: ELV[8:0]).
■Output Reference Voltage Adjustment Example (@VDD:5V)
When the output reference voltage is 100mV, set ELV[8]=0h and ELV[7:0]=240dec.
2500[mV]+(-0.002*VDD*240[dec])*5000[mV]=100[mV]
10. Output Span Voltage Adjustment
The output span voltage for the connected pressure sensor is adjusted, including the AK8998
internal error, by using the output span voltage adjustment register (address: 02h data: ESC[7:0]).
■Output Span Voltage Adjustment Example (@VDD:5V)
When the output is 3700mV, set ESC[7:0]=140dec (target span voltage 4800mV).
(3700[mV]-100[mV])*1.8*100/(100+0.25*(140))=4800[mV]
11. Offset Temperature Drift Adjustment
The offset temperature drift for the pressure sensor is adjusted, including the AK8998 internal
error, by using the offset voltage temperature drift adjustment register (address: 03, 04h data:
EOT[8:0]).
■Offset Temperature Drift Adjustment Example (@VDD:5V)
EOT[8]: Offset voltage adjustment sign bit
If unadjusted output is greater than the output reference voltage, set EOT[8]=1h.
If unadjusted output is smaller than the output reference voltage, set EOT[8]=0h.
EOT[7:0]: Offset voltage adjustment: Adjust in 0.144mV/ºC steps (@VDD: 5V).
If the offset voltage is +300mV (with respect to the output reference voltage e.g.100mV) at
Ta=85°C, set EOT[8]=1h, EOT[7:0]=35dec.
(100[mV]+300[mV])-(85[°C]-25[°C])*(0.144[mV/°C]*35[dec])=97.6[mV]
12. Sensitivity Temperature Drift Adjustment
The sensitivity temperature drift for the pressure sensor is adjusted, including the AK8998 internal
error, by using the sensitivity temperature drift adjustment register (address: 05, 06h data:
EST[8:0]).
■Sensitivity Temperature Drift Adjustment Example (@VDD:5V, ESTC[0]=1hex)
EST[8]: Sensitivity temperature drift adjustment sign bit (target span voltage 4800mV)
If unadjusted output is greater than 4800mV (with respect to the output reference voltage) at
Ta=85°C, set EST[8]=1h.
If unadjusted output is smaller than 4800mV (with respect to the output reference voltage) at
Ta=85°C, set EST[8]=0h.
EST[7:0]: Sensitivity temperature drift adjustment: Adjust in 18ppm/°C steps (@VDD: 5V).
If the output voltage is +4,400mV (with respect to the output reference voltage e.g.100mV) at
Ta=85°C, set EST[8]=0h, EST[7:0]=77dec.
4400[mV])+(85[°C]-25[°C])*(18[ppm/°C]*77[dec])*4800[mV]=4799.2[mV]
13. Offset Voltage Fine Adjustment
The offset voltage error is caused by compensating the offset voltage temperature drift. The offset
voltage is adjusted using the offset voltage fine adjustment EEPROM (Address: 01h data:
EOCF[7:0]).
MSxxxxx-E-00
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2012/11