AD7746 Analog Devices, AD7746 Datasheet - Page 17

• 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

EXC SET-UP REGISTER
Address Pointer 0x09, Default Value 0x03
Capacitive channel excitation setup.
Table 15. EXC Set-Up Bit Map
Bit
Mnemonic
Default
Table 16.
Bit
7
6
5
4
3
2
1
0
Mnemonic
CLKCTRL
EXCON
EXCB
EXCB
EXCA
EXCA
EXCLVL1,
EXCLVL0
Description
The CLKCTRL bit should be set to 0 for the specified AD7745/AD7746 performance.
CLKCTRL = 1 decreases the excitation signal frequency and the modulator clock frequency by factor of 2.
This also increases the conversion time on all channels (capacitive, voltage, and temperature) by a factor of 2.
When EXCON = 0, the excitation signal is present on the output only during capacitance channel conversion.
When EXCON = 1, the excitation signal is present on the output during both capacitance and
voltage/temperature conversion.
EXCB = 1 enables EXCB pin as the excitation output.
EXCB = 1 enables EXCB pin as the inverted excitation output.
Only one of the EXCB or the EXCB bits should be set for proper operation.
EXCA = 1 enables EXCA pin as the excitation output.
EXCA = 1 enables EXCA pin as the inverted excitation output.
Only one of the EXCA or the EXCA bits should be set for proper operation.
Excitation Voltage Level.
EXCLVL1
0
0
1
1
Bit 7
CLKCTRL
0
Bit 6
EXCON
0
EXCLVL0
0
1
0
1
Bit 5
EXCB
0
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Voltage on Cap
±V
±V
±V
±V
DD
DD
DD
DD
/8
/4
/2
× 3/8
Bit 4
EXCB
0
Bit 3
EXCA
0
EXC Pin Low Level
V
V
V
0
DD
DD
DD
× 3/8
× 1/4
× 1/8
Bit 2
EXCA
0
Bit 1
EXCLVL1
0
EXC Pin High Level
V
V
V
V
AD7745/AD7746
DD
DD
DD
DD
× 5/8
× 3/4
× 7/8
Bit 0
EXCLVL0
0