625 SPS, 24-Bit, 109 B Sigma-Delta ADC with On-Chip Buffer

The AD7762 is a high performance, 24-bit Σ-Δ analog-to-digital converter (ADC). It combines wide input bandwidth and high speed with the benefits of Σ-Δ conversion with a performance of 106 dB SNR at 625 kSPS, making it ideal for high speed data acquisition. Wide dynamic range combined with significantly reduced anti-aliasing requirements simplify the design process. An integrated buffer to drive the reference, a differential amplifier for signal buffering and level shifting, an overrange flag, internal gain and offset registers, and a low-pass digital FIR filter make the AD7762 a compact, highly integrated data acquisition device requiring minimal peripheral component selection. In addition, the device offers programmable decimation rates, and the digital FIR filter can be adjusted if the default characteristics are not appropriate to the application. The AD7762 is ideal for applications demanding high SNR without a complex front end signal processing design.

The differential input is sampled at up to 40 MSPS by an analog modulator. The modulator output is processed by a series of low-pass filters, the final filter having default or user-programmable coefficients. The sample rate, filter corner frequencies, and output word rate are set by a combination of the external clock frequency and the configuration registers of the AD7762.

The reference voltage supplied to the AD7762 determines the analog input range. With a 4 V reference, the analog input range is ±3.2 V differential biased around a common mode of 2 V. This common mode biasing can be achieved using the on-chip differential amplifier, further reducing the external signal conditioning requirements.

The AD7762 is available in an exposed paddle, 64-lead TQFP and is specified over the industrial temperature range from −40°C to +85°C.

APPLICATIONS

* Data acquisition systems

* Vibration analysis

* Instrumentation

* 120 dB dynamic range at 78 kHz output data rate

* 109 dB dynamic range at 625 kHz output data rate

* 112 dB SNR at 78 kHz output data rate

* 106 dB SNR at 625 kHz output data rate

* 625 kHz maximum fully filtered output word rate

* Low pass FIR filter with default or user programmable coefficients