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AD7825:  3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs

Product Details


The AD7822/AD7825/AD7829 are high speed, 1-, 4-, and 8-channel, microprocessor-compatible, 8-bit analog-to-digital converters with a maximum throughput of 2 MSPS. The AD7822/ AD7825/AD7829 contain an on-chip reference of 2.5 V (2% tolerance); a track-and-hold amplifier; a 420 ns, 8-bit half-flash ADC; and a high speed parallel interface. The converters can operate from a single 3 V ± 10% and 5 V ± 10% supply.

The AD7822/AD7825/AD7829 combine the convert start and power-down functions at one pin, that is, the CONVST pin. This allows a unique automatic power-down at the end of a conversion to be implemented. The logic level on the CONVST pin is sampled after the end of a conversion when an EOC (end of conversion) signal goes high. If it is logic low at that point, the ADC is powered down. The AD7822 and AD7825 also have a separate power-down pin (see the Operating Modes section).

The parallel interface is designed to allow easy interfacing to microprocessors and DSPs. Using only address decoding logic, the parts are easily mapped into the microprocessor address space. The EOC pulse allows the ADCs to be used in a stand-alone manner (see the Parallel Interface section.)

The AD7822 and AD7825 are available in 20-lead and 24-lead, 0.3" wide, plastic dual in-line packages (PDIP); 20-lead and 24-lead standard small outline packages (SOIC); and 20-lead and 24-lead thin shrink small outline packages (TSSOP). The AD7829 is available in a 28-lead, 0.6" wide PDIP; a 28-lead SOIC; and a 28-lead TSSOP.

Product Highlights

  1. Fast Conversion Time. The AD7822/AD7825/AD7829 have a conversion time of 420 ns. Faster conversion times maximize the DSP processing time in a real-time system.
  2. Analog Input Span Adjustment. The VMID pin allows the user to offset the input span. This feature can reduce the requirements of single-supply op amps and take into account any system offsets.
  3. FPBW (Full Power Bandwidth) of Track-and-Hold. The track-and-hold amplifier has an excellent high frequency performance. The AD7822/AD7825/AD7829 are capable of converting full-scale input signals up to a frequency of 10 MHz. This makes the parts ideally suited to subsampling applications.
  4. Channel Selection. Channel selection is made without the necessity of writing to the part.

Applications

  • Data acquisition systems, DSP front ends
  • Disk drives
  • Mobile communication systems, subsampling applications

FEATURES and BENEFITS

  • 8-bit half-flash ADC with 420 ns conversion time
  • 1, 4 and 8 Single-Ended Analog Input Channels Available with Input Offset Adjust
  • On-Chip Track-and-Hold
  • SNR Performance Given for Input Frequencies Up to 10 MHz
  • Automatic Power-Down at the End of Conversion
  • On-Chip Reference (2.5 V)
  • Wide Operating Supply Range 3 V ± 10% and 5 V ± 10%
  • Input Ranges:
    0 V to 2 V p-p, VDD = 3 V ± 10%
    0 V to 2.5 V p-p, VDD = 5 V ± 10%
  • Flexible Parallel Interface with EOC Pulse to Allow Stand-Alone Operation

Functional Block Diagram for AD7825

Documentation

Title Content Type File Type
AD7822/AD7825/AD7829: 3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs Data Sheet  (Rev C, 08/2006) (pdf, 518 kB) Data Sheets PDF
AN-215: Designer's Guide to Flash-ADC Testing, Part 1, 2 & 3  (pdf, 1596 kB)
Flash ADCs Provide the Basis for High Speed Conversion.
Application Notes PDF
AN-592: Application Considerations for the Convert Start Input (CONVST Bar) of the AD7822/AD7825/AD7827/AD7829  (pdf, 37 kB) Application Notes PDF
MS-2210: Designing Power Supplies for High Speed ADC  (pdf, 327 kB) Technical Articles PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Evaluation Kits & Symbols & Footprints

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

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Price, packaging, availability

AD7825 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD7825BRUZ Status: Production 24 ld TSSOP 24 Ind Tube, 62 $4.62 $3.61 Y  Material Info PCN Purchase Sample
AD7825BRUZ-REEL Status: Production 24 ld TSSOP 24 Ind Reel, 2500 - $3.61 Y  Material Info PCN Purchase
AD7825BRUZ-REEL7 Status: Production 24 ld TSSOP 24 Ind Reel, 1000 - $3.61 Y  Material Info PCN Purchase
AD7825BRZ Status: Production 24 ld SOIC - Wide 24 Ind Tube, 31 $4.62 $3.61 Y  Material Info PCN Purchase Sample
AD7825BRZ-REEL Status: Production 24 ld SOIC - Wide 24 Ind Reel, 1000 - $3.61 Y  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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