AD7746

24-bit, 2 Channel Capacitance to Digital Converter
Manufactured by:

Product Details

The AD7745/AD7746 are a high resolution, Σ-Δ capacitance-to-digital converter (CDC). The capacitance to be measured is connected directly to the device inputs. The architecture fea-tures inherent high resolution (24-bit no missing codes, up to 21-bit effective resolution), high linearity (±0.01%), and high accuracy (±4 fF factory calibrated). The AD7745/AD7746 capacitance input range is ±4 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 AD7745 has one capacitance input channel, while the AD7746 has two channels. Each channel can be configured as single-ended or differential. The AD7745/AD7746 are designed for floating capacitive sensors. For capacitive sensors with one plate connected to ground, the AD7747 is recommended.

The parts have 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 parts have 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 AD7745/AD7746 have a 2-wire, I2C-compatible serial interface. Both parts can operate with a single power supply from 2.7 V to 5.25 V. They are specified over the automotive temperature range of –40°C to +125°C and are housed in a 16-lead TSSOP package.

Applications

Automotive, Industrial and Medical Systems for:

  • Pressure Measurement
  • Position Sensors
  • Level Sensors
  • Flowmeters
  • Humidity Sensors
  • Impurity Detection

Product Lifecycle

checked Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits

X +

Product Details

The EVAL-AD7746EBZ is a fully featured evaluation board for the AD7746. The evaluation board is operated with a PC via a standard USB connection with software provided enabling the user to perform detailed analysis of the CDC's performance. This software includes the technical note describing the operation and set up of the evaluation board.

Design Resources

X +

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

AD7746 Material Declaration
PCN-PDN Information Quality And Reliability Symbols and Footprints

Discussions

X+

Didn't find what you were looking for?

Reviews

X+

Overview

5 Reviews
5 out of 5 (100%) customers recommend this product.
Quality
1
2
3
4
5
Reliability
1
2
3
4
5
Features
1
2
3
4
5

Most Helpful Review

by carlos
The IC works as expected. Although the information on the documentation was not enough for a simple operation. It does not show a diagram when using both channels, it does not show an example of the algorithm to use for configuration or programming it.

Most Recent Review

by Franko
For proof of concept it can be good because it has good resolution and it can be interfaced with a host controller. However if we need high resolution (eg. 21 bits), it requires 109ms to complete a conversion, in some applications it can be critical. Also, it could be good to have programmable I2C address, because since it is unique, it doesn't allow to connect several of them on the same I2C Bus. I2C Bus multiplexers are limited also in number. There is no 24-bits resolution CDC multichannel in the market, and it could be a good choice to develop protoypes in that way with more devices (CDC's) controlled by I2C.

All Reviews

by Franko, 13 May 14
Good for first prototypes
For proof of concept it can be good because it has good resolution and it can be interfaced with a host controller. However if we need high resolution (eg. 21 bits), it requires 109ms to complete a conversion, in some applications it can be critical. Also, it could be good to have programmable I2C address, because since it is unique, it doesn't allow to connect several of them on the same I2C Bus. I2C Bus multiplexers are limited also in number. There is no 24-bits resolution CDC multichannel in the market, and it could be a good choice to develop protoypes in that way with more devices (CDC's) controlled by I2C.
Was this Helpful?Helpful(1)
by philiprun, 13 May 14
great features and excellent functions
I like AD7746, it is the only one able to measure .
Was this Helpful?Helpful(1)
by Anonymous, 13 May 14
Excellent AD7746
AD 7746 greatly help us improve our research. The service of Analog is also very nice.
Was this Helpful?Helpful(0)
by carlos, 4 Mar 14
Good IC not so good documentation
The IC works as expected. Although the information on the documentation was not enough for a simple operation. It does not show a diagram when using both channels, it does not show an example of the algorithm to use for configuration or programming it.
Was this Helpful?Helpful(1)
by Sampath, 12 May 13
Can have more channels
Well, I wouldn't mind having an IC that traded off refresh rate for some kind multiplexing (8channels ?)
Was this Helpful?Helpful(0)

Sample & Buy

X+
Back
Check Inventory

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


Price Table Help

 
Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.