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 features 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:
Features and Benefits▪ Resolution: 0.1°C, accuracy: ±2°C ▪ 2.7 V to 5.25 V single-supply operation ▪ 0.7 mA current consumption | Analog to Digital ConvertersReference Designs |
| Document | note |
| AD7745/AD7746: 24-Bit Capacitance to Digital Converter with Temperature Sensor Data Sheet (Rev. 0) | PDF 773 kB |
| Document | note |
| AN-1301: Using CDCs to Control Motion for Sample Aspiration (Rev. 0) | PDF 169 kB |
| Document | note |
| Leading Inside Advertorials: Providing an Edge in Capacitive Sensor Applications | PDF 85 kB |
| Document | note |
| Part Number | Package | Packing Qty | Temp Range | Price 100-499 | Price 1000+ | RoHS |
|---|---|---|---|---|---|---|
| AD7745ARUZ Production | 16 ld TSSOP | OTH 96 | -40 to 125C | 5.46 | 4.66 | Y |
| AD7745ARUZ-REEL Production | 16 ld TSSOP | REEL 2500 | -40 to 125C | 0 | 4.66 | Y |
| AD7745ARUZ-REEL7 Production | 16 ld TSSOP | REEL 1000 | -40 to 125C | 0 | 4.66 | Y |
| Part Number | Description | Price | RoHS |
|---|---|---|---|
| EVAL-AD7746EBZ | Evaluation Board | 59 | Y |
