AD7746 Analog Devices, AD7746 Datasheet - Page 19

• Manufacturer Part Number: AD7746
• Description: 24-bit, 2 Channel Capacitance to Digital Converter
• Manufacturer: Analog Devices

Specifications of AD7746

• Resolution (bits): 24bit
• # Chan: 2
• Sample Rate: n/a
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (2Vref) p-p,± 4 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

CAP DAC A REGISTER
Address Pointer 0x0B, Default Value 0x00
Capacitive DAC setup.
Table 19. Cap DAC A Register Bit Map
Bit
Mnemonic
Default
Table 20.
Bit
7
6-1
CAP DAC B REGISTER
Address Pointer 0x0C, Default Value 0x00
Capacitive DAC setup.
Table 21. Cap DAC B Register Bit Map
Bit
Mnemonic
Default
Table 22.
Bit
7
6-1
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.
Mnemonic
DACAENA
DACA
Mnemonic
DACBENB
DACB
Bit 7
DACAENA
0
Description
DACAENA = 1 connects capacitive DACA to the positive capacitance input.
DACA value, Code 0x00 ≈ 0 pF, Code 0x7F ≈ full range.
Bit 7
DACBENB
0
Description
DACBENB = 1 connects capacitive DACB to the negative capacitance input.
DACB value, Code 0x00 ≈ 0 pF, Code 0x7F ≈ full range.
Bit 6
Bit 6
Bit 5
Bit 5
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Bit 4
Bit 4
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.
DACA—7-Bit Value
DACB—7-bit value
Bit 3
Bit 3
0x00
0x00
Bit 2
Bit 2
Bit 1
Bit 1
AD7745/AD7746
Bit 0
Bit 0