High Speed, µP-Compatible, CMOS, 8-Bit Sampling ADC
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 (vs. 1.36 µs for the AD7820) and 100 kHz signal bandwidth (vs. 6.4 kHz). The sampling instant is better defined and occurs on the falling edge of WR of RD. The provision for 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.
The AD7821 has a built-in track-and-hold function capable of digitizing full-scale signals up to 100 kHz max. It also uses a half-flash conversion technique that eliminates the need to generate a CLK signal for the ADC.
The AD7821 is designed with standard microprocessor control signals (CS, RD, WR, RDY, INT) and latched, three-state data outputs capable of interfacing to high-speed data buses. An overflow output (OFL) is also provided for cascading devices to achieve higher resolution.
The AD7821 is fabricated in Linear-Compatible CMOS (LC2MOS), an advanced, mixed technology process combining precision bipolar circuits with low-power CMOS logic. The part features a low power dissipation of 50 mW.
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At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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