3 V/5 V, 2 MSPS, 8-Bit, 8-Channel ADC

AD7829-1

Rev. 0

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FEATURES

8-bit half-flash ADC with 420 ns conversion time

Eight single-ended analog input channels

Available with input offset adjust

On-chip track-and-hold

SNR performance given for input frequencies

up to10 MHz

On-chip reference (2.5 V)

Automatic power-down at the end of conversion

Wide operating supply range

3 V ± 10% and 5 V ± 10%

Input ranges

Flexible parallel interface with EOC pulse to allow

stand-alone operation

APPLICATIONS

Data acquisition systems, DSP front ends

Disk drives

Mobile communication systems, subsampling

applications

GENERAL DESCRIPTION

The AD7829-1 is a high speed 8-channel, microprocessor-

compatible, 8-bit analog-to-digital converter with a maximum

throughput of 2 MSPS. The AD7829-1 contains 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 converter can operate from a single 3 V ± 10%

and 5 V ± 10% supply.

The AD7829-1 combines 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, and if it is logic low at that point, the ADC is

powered down. 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).

FUNCTIONAL BLOCK DIAGRAM

CONVST

PARALLEL

PORT

EOC

RD

CS

AGND

A0

A1

A2

COMP

2.5V

REF

CONTROL

LOGIC

DGND

INPUT

MUX

T/H

BUF

DB0

DB7

8-BIT

HALF

FLASH

ADC

Figure 1.

The AD7829-1 is available in a 28-lead, wide body, small outline

IC (SOIC_W) and a 28-lead thin shrink small outline package

(TSSOP).

PRODUCT HIGHLIGHTS

1.

Fast Conversion Time. The AD7829-1 has a conversion

time of 420 ns. Faster conversion times maximize the DSP

processing time in a real-time system.

2.

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 excellent high frequency

performance. The AD7829-1 is capable of converting full-

scale input signals up to a frequency of 10 MHz, making

the parts ideally suited to subsampling applications.

4.

Channel Selection. Channel selection is made without the

necessity of writing to the part.