2 LC MOS High Speed, P Compatible a 8-Bit ADC with Track/Hold Function AD7821 FUNCTIONAL BLOCK DIAGRAM FEATURES Fast Conversion Time: 660 ns Max 100 kHz Track-and-Hold Function 1 MHz Sample Rate Unipolar and Bipolar Input Ranges Ratiometric Reference Inputs No External Clock Extended Temperature Range Operation Skinny 20-Lead DlPs, SOIC, and 20-Terminal Surface-Mount Packages GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7821 is a high speed, 8-bit, sampling, analog-to-digital 1. Fast Conversion Time converter that offers improved performance over the popular The half-flash conversion technique, coupled with fabrication 2 AD7820. It offers a conversion time of 660 ns (versus 1.36 s on Analog Devices LC MOS process, enables a very fast con- for the AD7820) and 100 kHz signal bandwidth (versus 6.4 version time. The conversion time for the WR-RD mode is kHz). The sampling instant is better defined and occurs on the 660 ns, with 700 ns for the RD mode. falling edge of WR or RD. The provision of a V pin (Pin 19) SS 2. Built-In Track-and-Hold allows the part to operate from 5 V supplies and to digitize This allows input signals with slew rates up to 1.6 V/s to be bipolar input signals. Alternatively, for unipolar inputs, the V pin SS converted to 8 bits without an external track-and-hold. This can be grounded and the AD7821 will operate from a single +5 V corresponds to a 5 V peak-to-peak, 100 kHz sine wave signal. supply, like the AD7820. 3. Total Unadjusted Error The AD7821 has a built-in track-and-hold function capable of The AD7821 features an excellent total unadjusted error figure digitizing full-scale signals up to 100 kHz max. It also uses a of less than 1 LSB over the full operating temperature range. half-flash conversion technique that eliminates the need to gen- 4. Unipolar/Bipolar Input Ranges erate a CLK signal for the ADC. The AD7821 is specified for single-supply (+5 V) operation The AD7821 is designed with standard microprocessor control with a unipolar full-scale range of 0 to +5 V, and for dual-supply signals (CS, RD, WR, RDY, INT) and latched, three-state data (5 V) operation with a bipolar input range of 2.5 V. Typical outputs capable of interfacing to high speed data buses. An performance characteristics are given for other input ranges. overflow output (OFL) is also provided for cascading devices to 5. Dynamic Specifications for DSP Users achieve higher resolution. In addition to the traditional ADC specifications, the The AD7821 is fabricated in Linear Compatible CMOS AD7821 is specified for ac parameters, including signal-to- 2 (LC MOS), an advanced, mixed technology process combining noise ratio, distortion, and slew rate. precision bipolar circuits with low power CMOS logic. The part features a low power dissipation of 50 mW. REV. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties that Tel: 781/329-4700 www.analog.com may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 Analog Devices, Inc., 2002AD7821* PRODUCT PAGE QUICK LINKS Last Content Update: 02/23/2017 COMPARABLE PARTS DESIGN RESOURCES View a parametric search of comparable parts. AD7821 Material Declaration PCN-PDN Information DOCUMENTATION Quality And Reliability Application Notes Symbols and Footprints AN-299: Simple Circuit Provides Ratiometric Reference Levels for AD782X Family of Half-Flash ADCs DISCUSSIONS Data Sheet View all AD7821 EngineerZone Discussions. AD7821: High Speed, P-Compatible, CMOS, 8-Bit Sampling ADC Data Sheet SAMPLE AND BUY AD7821: Military Data Sheet Visit the product page to see pricing options. REFERENCE MATERIALS TECHNICAL SUPPORT Technical Articles Submit a technical question or find your regional support MS-2210: Designing Power Supplies for High Speed ADC number. DOCUMENT FEEDBACK Submit feedback for this data sheet. This page is dynamically generated by Analog Devices, Inc., and inserted into this data sheet. A dynamic change to the content on this page will not trigger a change to either the revision number or the content of the product data sheet. This dynamic page may be frequently modified.