AD7745 Datasheet, PDF (19/28 Pages) Analog Devices – 24-Bit Capacitance-to-Digital Converter with Temperature Sensor

CAP DAC A REGISTER
Address Pointer 0x0B, Default Value 0x00
Capacitive DAC setup.
Table 19. Cap DAC A Register Bit Map
Bit
Bit 7
Bit 6
Mnemonic
DACAENA
Default
0
Bit 5
Bit 4
Bit 3
Bit 2
DACA—7-Bit Value
0x00
Table 20.
Bit Mnemonic
7
DACAENA
6-1 DACA
Description
DACAENA = 1 connects capacitive DACA to the positive capacitance input.
DACA value, Code 0x00 ≈ 0 pF, Code 0x7F ≈ full range.
AD7745/AD7746
Bit 1
Bit 0
CAP DAC B REGISTER
Address Pointer 0x0C, Default Value 0x00
Capacitive DAC setup.
Table 21. Cap DAC B Register Bit Map
Bit
Bit 7
Bit 6
Mnemonic
DACBENB
Default
0
Bit 5
Bit 4
Bit 3
Bit 2
DACB—7-bit value
0x00
Bit 1
Bit 0
Table 22.
Bit Mnemonic
7
DACBENB
6-1 DACB
Description
DACBENB = 1 connects capacitive DACB to the negative capacitance input.
DACB value, Code 0x00 ≈ 0 pF, Code 0x7F ≈ full range.
CAP OFFSET CALIBRATION REGISTER
16 Bits, Address Pointer 0x0D, 0x0E,
Default Value 0x8000
The capacitive offset calibration register holds the capacitive
channel zero-scale calibration coefficient. The coefficient is
used to digitally remove the capacitive channel offset. The
register value is updated automatically following the execution
of a capacitance offset calibration. The capacitive offset calibra-
tion resolution (cap offset register LSB) is less than 32 aF; the
full range is 1 pF.
On the AD7746, the register is shared by the two capacitive
channels. If the capacitive channels need to be offset-calibrated
individually, the host controller software should read the
AD7746 capacitive offset calibration register values after
performing the offset calibration on individual channels and
then reload the values back to the AD7746 before executing
conversion on a different channel.
CAP GAIN CALIBRATION REGISTER
16 Bits, Address Pointer 0x0F, 0x10,
Default Value 0xXXXX
Capacitive gain calibration register. The register holds the
capacitive channel full-scale factory calibration coefficient.
On the AD7746, the register is shared by the two capacitive
channels.
VOLT GAIN CALIBRATION REGISTER
16 Bits, Address Pointer 0x11,0x12,
Default Value 0xXXXX
Voltage gain calibration register. The register holds the voltage
channel full-scale factory calibration coefficient.
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