ANALOG DEVICES AD7874 Data Sheet

LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System

AD7874

FEATURES

FUNCTIONAL BLOCK DIAGRAM

Four On-Chip Track/Hold Amplifiers Simultaneous Sampling of 4 Channels VDD VDD

INT CS RD CONVST

Fast 12-Bit ADC with 8 ms Conversion Time/Channel 29 k Hz Sample Rate for All Four Channels

INTERNAL

On-Chip Reference CONTROL LOGIC CLK

CLOCK

TRACK/

610 V Input Range VIN1

HOLD 1

65 V Supplies

TRACK/

VIN2 COMP

APPLICATIONS HOLD 2

SAR MUX

Sonar

TRACK/

Motor Controllers HOLD 3

DATA DB0

Adaptive Filters

REGISTERS

TRACK/ DB11

Digital Signal Processing VIN4

HOLD 4

REFERENCE BUFFER

12-BIT DAC

REF IN

AD7874

GENERAL DESCRIPTION

The AD7874 is a four-channel simultaneous sampling, 12-bit REF OUT3V

REFERENCE

data acquisition system. The part contains a high speed 12-bit ADC, on-chip reference, on-chip clock and four track/hold am- AGND DGND VSS plifiers. This latter feature allows the four input channels to be sampled simultaneously, thus preserving the relative phase

PRODUCT HIGHLIGHTS

information of the four input channels, which is not possible if

1. Simultaneous Sampling of Four Input Channels.

all four channels share a single track/hold amplifier. This makes

Four input channels, each with its own track/hold amplifier,

the AD7874 ideal for applications such as phased-array sonar

allow simultaneous sampling of input signals. Track/hold ac-

and ac motor controllers where the relative phase information is

quisition time is 2 µs, and the conversion time per channel is

important.

8 µs, allowing 29 k Hz sample rate for all four channels.

The aperture delay of the four track/hold amplifiers is small and

2. Tight Aperture Delay Matching.

specified with minimum and maximum limits. This allows sev-

The aperture delay for each channel is small and the aperture

eral AD7874s to sample multiple input channels simultaneously

delay matching between the four channels is less than 4 ns.

without incurring phase errors between signals connected to

Additionally, the aperture delay specification has upper and

several devices. A reference output/reference input facility also

lower limits allowing multiple AD7874s to sample more than

allows several AD7874s to be driven from the same reference

four channels.

source.

3. Fast Microprocessor Interface.

In addition to the traditional dc accuracy specifications such as

The high speed digital interface of the AD7874 allows direct

linearity, full-scale and offset errors, the AD7874 is also fully

connection to all modern 16-bit microprocessors and digital

specified for dynamic performance parameters including distor-

signal processors.

tion and signal-to-noise ratio. The AD7874 is fabricated in Analog Devices’ Linear Compat- ible CMOS (LC2MOS) process, a mixed technology process that combines precision bipolar circuits with low-power CMOS logic. The part is available in a 28-pin, 0.6" wide, plastic or her- metic dual-in-line package (DIP), in a 28-terminal leadless ce- ramic chip carrier (LCCC) and in a 28-pin SOIC.

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which may result from its use. No license is granted by implication or One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. otherwise under any patent or patent rights of Analog Devices. Tel: 617/329-4700 Fax: 617/326-8703