[AK4675]
■ SAR 10bit ADC
The AK4675 incorporates a 10-bit successive approximation resistor A/D converter for DC measurement.
The A/D converter output is a straight binary format as shown in Table 112:
Input Voltage
Output Code
3FFH
3FEH
:
~
~
AVDD
(AVDD−1.5LSB)
(AVDD−1.5LSB)
(AVDD−2.5LSB)
:
0.5LSB
0
~
~
1.5LSB
0.5LSB
001H
000H
Table 112. Output Code
When PMSAD bit is set to “1”, 10bit ADC is powered-up. When the control register is read, A/D conversion is executed
and data is output.
10bit ADC supports 3 kinds of analog input. A1-0 bits select the measurement modes.
Mode
A1
0
0
1
1
A0
0
1
0
1
Input Channel
SAIN1
0
1
2
3
(default)
SAIN2
SAIN3
N/A
Table 113. SAR ADC Measurement Mode
<SAR ADC Execute Sequence (in case that the interrupt function is enabled.)>
(1) Select the measurement mode by A1-0 bits and set PMSAD bit = “1” to power-up SAR ADC.
(2) Read Addr=5BH so that A/D conversion is executed and MSB 8bit data is output.
(3) Additionally read Addr=5CH then LSB 2bit data is output.
<SAR ADC Execute Sequence (in case that the interrupt function is disabled.)>
(1) GPOM1 bit should be set to “1”. The GPO1 pin can be used as the interrupt output pin.
(2) Select the measurement mode by A0 bit.
(3) The GPO1 pin goes to “H” when the input DC voltage of the SAIN1 or SAIN2 pin (selected by A0 bit) is higher than
the input voltage of the SAIN3 pin.
(4) After CPU detects the GPO1 pin = “H”, set GPOM1 bit = “0” and PMSAD bit = “1” to power-up SAR ADC.
(5) Read Addr=5BH so that A/D conversion is executed and MSB 8bit data is output.
(6) Additionally read Addr=5CH then LSB 2bit data is output.
MS0963-E-00
2008/05
- 135 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
