AD7725

The AD7725 is a complete 16-bit, - analog-to-digital con-verter with on-chip, user-programmable signal conditioning. The output of the modulator is processed by three cascaded finite impulse response (FIR) filters, followed by a fully user-program-mable postprocessor. The postprocessor provides processing power of up to 130 million accumulates (MAC) per second. The user has complete control over the filter response, the filter coeffi- cients, and the decimation ratio.

The postprocessor permits the signal conditioning characteris- tics to be programmed through a parallel or serial interface. It is programmed by loading a user-defined filter in the form of a configuration file. This filter can be loaded from a DSP or an external serial EPROM. It is generated using a digital filter design package called Filter Wizard, which is available from the AD7725 section on the Analog Devices website. Filter Wizard allows the user to design different filter types and generates the appropriate configuration file to be down- loaded to the postprocessor. The AD7725 also has an internal default filter for evaluation purposes.

It provides 16-bit performance for input bandwidths up to 350 kHz with an output word rate of 900 kHz maximum. The input sample rate is set either by the crystal oscillator or an external clock. This part has an accurate on-chip 2.5 V reference for the modu- lator. A reference input/output function allows either the internal reference or an external system reference to be used as the reference source for the modulator. The device is available in a 44-lead MQFP package and is speci- fied over a 40 °C to +85° C temperature range.