GENERAL DESCRIPTION
The AD7747 is a high-resolution,
Σ−∆ capacitance-to-digital converter (CDC).
The capacitance to be measured is connected
directly to the device inputs. The architecture
features inherent high resolution (24-bit no missing
codes, up to 18 bit effective resolution),
high linearity (±0.01%), and high accuracy (±8 fF
factory calibrated). The AD7747 capacitance input range is
±8 pF (changing), while it can accept up to 17 pF common-
mode capacitance (not changing), which can be balanced by a
programmable on-chip digital-to-capacitance converter
(CAPDAC).
The AD7747 is designed for single ended or differential
capacitive sensors with one plate connected to ground.
For floating (not grounded) capacitive sensors, the AD7745
or AD7746 are recommended.
The part has an on-chip temperature sensor with a resolution
of 0.1°C and accuracy of ±2°C. The on-chip voltage reference
and the on-chip clock generator eliminate the need for any
external components in capacitive sensor applications.
The part has a standard voltage input, which together with
the differential reference input allows easy interface to
an external temperature sensor, such as an RTD, thermistor,
or diode.
The AD7747 has a 2-wire, IC-compatible serial interface. The
part can operate with a single power supply 2.7 V to 5.25 V.
It is specified over the automotive temperature range of
–40°C to +125°C and are housed in a 16-lead TSSOP package.
FEATURES
Capacitance-to-digital converter
New standard in single chip solutions
Interfaces to single or differential grounded sensors
Resolution down to 40 aF (that is, up to 18.5-bit ENOB)
Accuracy: 8 fF
Linearity: 0.01%
Common-mode (not changing) capacitance up to 17 pF
Full scale (changing) capacitance range ±8 pF
Update rate: 5 Hz to 45 Hz
Simultaneous 50 Hz and 60 Hz rejection at 8.1 Hz update
Active shield for shielding sensor connection
Temperature sensor on-chip
Resolution: 0.1°C, accuracy: ±2°C
Voltage input channel
Internal clock oscillator
2-wire serial interface (I 2C®-compatible)
Power
2.7 V to 5.25 V single-supply operation
1 mA current consumption
Operating temperature: –40°C to +125°C
16-lead TSSOP package
APPLICATIONS
Automotive, industrial, and medical systems for
Pressure measurement
Position sensing
Proximity sensing
Level sensing
Flowmeters
Impurity detection
OUTLINE DIMENSIONS
FUNCTIONAL BLOCK DIAGRAMS
Serial Interface Timing Diagram
TYPICAL APPLICATION DIAGRAM
ESD CAUTION
ESD (electrostatic discharge) sensitive device.
Electrostatic charges as high as 4000 V readily accumulate on the
human body and test equipment and can discharge without detection.
Although this product features proprietary ESD protection circuitry,
permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
FROM: Company Name: Aunytor Electronic (HK) Co.,Ltd
Contact Person: Charlotte
Skype: Aunytor
whatsapp：+86 13537622113
Email: carrot@aunytorchips.com