This Technical Note describes the evaluation board for the AD7785, which is a low power, 20-bit sigma-delta (Σ-Δ) ADC. The AD7785 is a complete analog front end for low frequency measurement applications. It contains three differential inputs and includes a low noise instrumentation amplifier, an embedded reference, and programmable current sources. The update rate can be varied from 4.17 Hz to 470 Hz. It also has an on-board clock, eliminating the need for an external clock. It employs a Σ-Δ conversion technique to realize up to 20 bits of no missing codes performance. The input signal is applied to an analog modulator. The modulator output is processed by an on-chip digital filter. The analog input channel of the AD7785 accepts analog input signals of ±VREF/gain, with gain equal to 1 to 128. With a gain of 64 and the update rate programmed to 16.7 Hz, the rms noise is 85 nV. Simultaneous 50 Hz/60 Hz rejection is available at this data update rate also.
Technical notes are available in Adobe Acrobat Portable Document Format (PDF). To download the Technical Note, select the link below:
EVAL-AD7785EBZ Technical Note (pdf, 950,740 bytes)
The software provided runs under Windows 2000 and will allow the user to control all the functions of the AD7785 via the USB port of a PC. The software should be installed by running the SETUP.EXE program.
AD7785 Software (zip, 22.2 MB)