Overview
The AD7746ARUZ, produced by Analog Devices Inc., is a high-resolution, Σ-Δ capacitance-to-digital converter (CDC) designed for precise capacitance measurements. This device is part of the AD7745/AD7746 family, which sets a new standard in single-chip solutions for capacitive sensing applications. The AD7746 features two capacitance input channels, each configurable as single-ended or differential, making it versatile for various sensing needs.
The device includes an on-chip temperature sensor with a resolution of 0.1°C and accuracy of ±2°C, as well as a voltage input channel and a differential reference input. This allows for easy integration with external temperature sensors such as RTDs, thermistors, or diodes. The AD7746 operates on a single supply voltage ranging from 2.7V to 5.25V and has a low current consumption of 0.7 mA, making it suitable for a wide range of applications.
Key Specifications
| Parameter | Min | Typ | Max | Unit | Test Conditions/Comments |
|---|---|---|---|---|---|
| Supply Voltage (VDD) | 2.7 | 5.25 | V | ||
| Current Consumption | 0.7 | mA | |||
| Operating Temperature | -40 | 125 | °C | ||
| Capacitive Input Range | ±4.096 | pF | Factory calibrated | ||
| Integral Nonlinearity (INL) | ±0.01% | % of FSR | No missing codes | ||
| Resolution | 24 Bit | No missing codes | |||
| Effective Resolution | 19 Bit | Conversion time = 62 ms | |||
| Output Noise, rms | 2 aF/√Hz | See Table 5 | |||
| Absolute Error | ±4 fF | 25°C, VDD = 5 V, after offset calibration | |||
| Update Rate | 10 | 90 | Hz | ||
| Package | 16-TSSOP (0.173, 4.40mm Width) |
Key Features
- High-resolution Σ-Δ capacitance-to-digital converter with up to 24-bit resolution and no missing codes
- Two capacitance input channels, each configurable as single-ended or differential
- On-chip temperature sensor with 0.1°C resolution and ±2°C accuracy
- Voltage input channel and differential reference input for easy integration with external temperature sensors
- Single supply operation from 2.7V to 5.25V and low current consumption of 0.7 mA
- 2-wire serial interface (I2C-compatible)
- High linearity (±0.01%) and high accuracy (±4 fF factory calibrated)
- Tolerant of parasitic capacitance to ground up to 60 pF
- Simultaneous 50 Hz and 60 Hz rejection at 16 Hz
Applications
- Automotive systems for pressure measurement, position sensing, level sensing, and flowmeters
- Industrial systems for various capacitive sensing applications
- Medical systems for precise measurements and sensing
- Humidity sensing and impurity detection
Q & A
- What is the resolution of the AD7746 capacitance-to-digital converter?
The AD7746 has a resolution of up to 24 bits with no missing codes, and an effective resolution of 19 bits at a conversion time of 62 ms.
- How many capacitance input channels does the AD7746 have?
The AD7746 has two capacitance input channels, each configurable as single-ended or differential.
- What is the operating temperature range of the AD7746?
The operating temperature range of the AD7746 is from -40°C to +125°C.
- What is the supply voltage range for the AD7746?
The AD7746 operates on a single supply voltage ranging from 2.7V to 5.25V.
- Does the AD7746 have an on-chip temperature sensor?
Yes, the AD7746 includes an on-chip temperature sensor with a resolution of 0.1°C and accuracy of ±2°C.
- What is the interface type of the AD7746?
The AD7746 uses a 2-wire serial interface (I2C-compatible).
- What is the typical current consumption of the AD7746?
The typical current consumption of the AD7746 is 0.7 mA.
- What are some common applications of the AD7746?
The AD7746 is commonly used in automotive, industrial, and medical systems for various capacitive sensing applications such as pressure measurement, position sensing, level sensing, and flowmeters.
- How does the AD7746 handle parasitic capacitance?
The AD7746 is tolerant of parasitic capacitance to ground up to 60 pF.
- Does the AD7746 have simultaneous noise rejection capabilities?
Yes, the AD7746 can reject both 50 Hz and 60 Hz noise at 16 Hz.
