AD7746 datasheet(19/28 Pages) AD

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AD7745/AD7746

Rev. 0| Page 19 of 28

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

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Mnemonic

DACAENA

DACA—7-Bit Value

Default

0x00

Table 20.

Bit

Mnemonic

Description

DACAENA

DACAENA = 1 connects capacitive DACA to the positive capacitance input.

6-1

DACA

DACA value, Code 0x00

≈ 0 pF, Code 0x7F ≈ full range.

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

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Mnemonic

DACBENB

DACB—7-bit value

Default

0x00

Table 22.

Bit

Mnemonic

Description

DACBENB

DACBENB = 1 connects capacitive DACB to the negative capacitance input.

6-1

DACB

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

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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