AD7746 Analog Devices, AD7746 Datasheet - Page 16

• 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

AD7745/AD7746
CAP SET-UP REGISTER
Address Pointer 0x07, Default Value 0x00
Capacitive channel setup.
Table 11. CAP Set-Up Register Bit Map
Bit
Mnemonic
Default
Table 12.
Bit
7
6
5
4-1
0
VT SET-UP REGISTER
Address Pointer 0x08, Default Value 0x00
Voltage/Temperature channel setup.
Table 13. VT Set-Up Register Bit Map
Bit
Mnemonic
Default
Table 14.
Bit
7
6
5
4
3-2
1
0
Mnemonic
CAPEN
CIN2
CAPDIFF
-
CAPCHOP
Mnemonic
VTEN
VTMD1
VTMD0
EXTREF
-
VTSHORT
VTCHOP = 1
Bit 7
CAPEN
0
Description
CAPEN = 1 enables capacitive channel for single conversion, continuous conversion, or calibration.
CIN2 = 1 switches the internal multiplexer to the second capacitive input on the AD7746.
DIFF = 1 sets differential mode on the selected capacitive input.
These bits must be 0 for proper operation.
The CAPCHOP bit should be set to 0 for the specified capacitive channel performance.
CAPCHOP = 1 approximately doubles the capacitive channel conversion times and slightly improves the
capacitive channel noise performance for the longest conversion times.
Bit 7
Description
VTEN = 1 enables voltage/temperature channel for single conversion, continuous conversion, or calibration.
Voltage/temperature channel input configuration.
VTMD1
0
0
1
1
EXTREF = 1 selects an external reference voltage connected to REFIN(+), REFIN(–) for the voltage input or the
V
EXTREF = 0 selects the on-chip internal reference. The internal reference must be used with the internal
temperature sensor for proper operation.
These bits must be 0 for proper operation.
VTSHORT = 1 internally shorts the voltage/temperature channel input for test purposes.
VTCHOP = 1 sets internal chopping on the voltage/temperature channel.
The VTCHOP bit must be set to 1 for the specified voltage/temperature channel performance.
VTEN
0
DD
monitor.
VTMD0
0
1
0
1
Bit 6
CIN2
0
Bit 6
VTMD1
0
Channel Input
Internal temperature sensor
External temperature sensor diode
V
External voltage input (VIN)
DD
monitor
Bit 5
CAPDIFF
0
Bit 5
VTMD0
0
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Bit 4
-
0
Bit 4
EXTREF
0
Bit 3
-
0
Bit 3
-
0
Bit 2
-
0
Bit 2
-
0
Bit 1
-
0
Bit 1
VTSHORT
0
Bit 0
CAPCHOP
0
Bit 0
VTCHOP
0