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AD7821:  High Speed, µP-Compatible, CMOS, 8-Bit Sampling ADC

Product Details

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.


  • 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 DIPs, SOIC, and
    Surface-Mount Packages

Functional Block Diagram for AD7821


Title Content Type File Type
AD7821: High Speed, µP-Compatible, CMOS, 8-Bit Sampling ADC Data Sheet (Rev B, 11/2002) (pdf, 811 kB) Data Sheets PDF
AD7821: Military Data Sheet  (Rev A, 07/2002) (pdf) Data Sheets PDF
AN-299: Simple Circuit Provides Ratiometric Reference Levels for AD782X Family of Half-Flash ADCs  (pdf, 170 kB) Application Notes PDF
ADI Warns Against Misuse of COTS Integrated Circuits  (pdf, 13 kB)
(Revised 1/03)
Invites Customer Participation in Creative Mil/Aero System Solutions
Recommended Reading PDF
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
Space Qualified Parts List  (pdf, 93 kB)
This document lists 67 (240+) space level products that are available from Analog Devices. Many of the products listed are state-of-the-art data conversion and signal processing products that were previously only available as commercial or military Class B products. Through our Space Products Group and MIL-PRF-38535 certified Level V (Class S) facility, we are pleased to offer these products to the space marketplace.
Aerospace Information PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

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Price, packaging, availability

AD7821 Model Options
Model Package Pins Temp.
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
5962-89518012A Status: Production 20 ld LCC 20 Mil Tube, 54 $139.04 $125.70 N  Material Info PCN Purchase
5962-8951801RA Status: Production 20 ld CerDIP 20 Mil Tube, 18 $71.47 $64.62 N  Material Info PCN Purchase
AD7821BCHIPS Status: Last Time Buy CHIPS OR DIE 0 Comm. Tray, 100 $10.47 $10.47 Y  Material Info PCN/PDN Contact ADI
AD7821BQ Status: Production 20 ld CerDIP 20 Ind Tube, 18 $19.98 $19.98 N  Material Info PCN Purchase
AD7821KN Status: Production 20 ld PDIP 20 Comm. Tube, 18 $12.46 $10.58 N  Material Info PCN Purchase
AD7821KNZ Status: Production 20 ld PDIP 20 Comm. Tube, 18 $10.79 $9.16 Y  Material Info PCN Purchase
AD7821KPZ Status: Production 20 ld PLCC 20 Comm. Tube, 49 $12.60 $10.16 Y  Material Info PCN Purchase
AD7821KPZ-REEL Status: Production 20 ld PLCC 20 Comm. Reel, 1000 - $10.16 Y  Material Info PCN Purchase
AD7821KRZ Status: Production 20 ld SOIC - Wide 20 Comm. Tube, 37 $12.00 $9.68 Y  Material Info PCN Purchase
AD7821KRZ-REEL Status: Production 20 ld SOIC - Wide 20 Comm. Reel, 1000 - $9.68 Y  Material Info PCN Purchase
AD7821TQ Status: Production 20 ld CerDIP 20 Mil Tube, 18 $49.90 $49.90 N  Material Info PCN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

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