AD7746 Analog Devices, AD7746 Datasheet - Page 2

• 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
TABLE OF CONTENTS
Specifications..................................................................................... 3
Timing Specifications....................................................................... 5
Absolute Maximum Ratings............................................................ 6
Pin Configurations and Function Descriptions ........................... 7
Typical Performance Characteristics ............................................. 8
Output Noise and Resolution Specifications .............................. 11
Serial Interface ................................................................................ 12
Register Descriptions ..................................................................... 14
REVISION HISTORY
4/05—Revision 0: Initial Version
Read Operation........................................................................... 12
Write Operation.......................................................................... 12
AD7745/AD7746 Reset ............................................................. 13
General Call................................................................................. 13
Status Register ............................................................................. 15
Cap Data Register....................................................................... 15
VT Data Register ........................................................................ 15
Cap Set-Up Register ................................................................... 16
VT Set-Up Register .................................................................... 16
EXC Set-Up Register .................................................................. 17
Configuration Register .............................................................. 18
Cap DAC A Register................................................................... 19
Cap DAC B Register................................................................... 19
Cap Offset Calibration Register................................................ 19
Rev. 0 | Page 2 of 28
Circuit Description......................................................................... 20
Outline Dimensions ....................................................................... 25
Cap Gain Calibration Register.................................................. 19
Volt Gain Calibration Register ................................................. 19
Overview ..................................................................................... 20
Capacitance-to-Digital Converter ........................................... 20
Excitation Source........................................................................ 20
CAPDAC ..................................................................................... 21
Single-Ended Capacitive Input................................................. 21
Differential Capacitive Input .................................................... 21
Parasitic Capacitance to Ground.............................................. 22
Parasitic Resistance to Ground................................................. 22
Parasitic Parallel Resistance ...................................................... 22
Parasitic Serial Resistance ......................................................... 23
Capacitive Gain Calibration ..................................................... 23
Capacitive System Offset Calibration ...................................... 23
Internal Temperature Sensor .................................................... 23
External Temperature Sensor ................................................... 24
Voltage Input............................................................................... 24
V
Typical Application Diagram.................................................... 24
Ordering Guide .......................................................................... 25
DD
Monitor ................................................................................ 24