The AD7821 is a high speed, 8-bit, sampling, analog-to-digital converter that offers improved performance over the popular AD7820. It offers a conversion time of 660 ns (versus 1.36 µs for the AD7820) and 100 kHz signal bandwidth (versus 6.4 kHz). The sampling instant is better defined and occurs on the falling edge of WR or RD. The provision of a VSS pin (Pin 19) allows the part to operate from ±5 V supplies and to digitize bipolar input signals. Alternatively, for unipolar inputs, the VSS pin can be grounded and the AD7821 will operate from a single +5 V supply, like the AD7820.