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AD7938: Description8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer; File Size565KB，32 Pages; ManufacturerADI; Websitehttps://www.analog.com

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AD7938 Overview

8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer

User Manual

【User Guides】UG-221: Evaluation Board for the ADM3052 Isolated CAN Transceiver with Integrated High Voltage, Bus Side Linear Regulato

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Preliminary Technical Data

FEATURES

Fast throughput rate: 1.5 MSPS

Specified for V

of 2.7 V to 5.25 V

Low power

8 mW max at 1.5 MSPS with 3 V supplies

16 mW max at 1.5 MSPS with 5 V supplies

8 analog input channels with a sequencer

Software configurable analog inputs

8-channel single-ended inputs

4-channel fully differential inputs

4-channel pseudo-differential inputs

7-channel pseudo-differential inputs

Accurate on-chip 2.5 V reference

Wide input bandwidth

70 dB SNR at 50 kHz input frequency

No pipeline delays

High speed parallel interface—word/byte modes

Full shutdown mode: 1 µA max

32-lead LFCSP and TQFP package

8-Channel, 1.5 MSPS, 12-Bit and 10-Bit

Parallel ADCs with a Sequencer

AD7938/AD7939

FUNCTIONAL BLOCK DIAGRAM

REFIN/

AGND

AD7938/AD7939

2.5V

VREF

12-/10-BIT

SAR ADC

AND

CONTROL

CLKIN

CONVST

BUSY

REFOUT

I/P

MUX

T/H

SEQUENCER

PARALLEL INTERFACE/CONTROL REGISTER

DRIVE

DB0 DB11

CS RD WR W/B

DGND

Figure 1.

GENERAL DESCRIPTION

The AD7938/AD7939 are 12-bit and 10-bit, high speed, low

power, successive approximation (SAR) ADCs. The parts

operate from a single 2.7 V to 5.25 V power supply and feature

throughput rates up to 1.5 MSPS. The parts contain a low noise,

wide bandwidth, differential track-and-hold amplifier that can

handle input frequencies up to 20 MHz.

The AD7938/AD7939 feature eight analog input channels with

a channel sequencer that allow a preprogrammed selection of

channels to be converted sequentially. These parts can operate

with either single-ended, fully differential, or pseudo-

differential analog inputs.

The conversion process and data acquisition are controlled

using standard control inputs that allow easy interfacing with

microprocessors and DSPs. The input signal is sampled on the

falling edge of CONVST and the conversion is also initiated at

this point.

The AD7938/AD7939 have an accurate on-chip 2.5 V reference

that can be used as the reference source for the analog-to-digital

conversion. Alternatively, this pin can be overdriven to provide

an external reference.

These parts use advanced design techniques to achieve very low

power dissipation at high throughput rates. They also feature

flexible power management options. An on-chip control register

allows the user to set up different operating conditions,

including analog input range and configuration, output coding,

power management, and channel sequencing.

PRODUCT HIGHLIGHTS

High throughput with low power consumption.

Eight analog inputs with a channel sequencer.

Accurate on-chip 2.5 V reference.

Software configurable analog inputs. Single-ended, pseudo-

differential, or fully differential analog inputs that are

software selectable.

Single-supply operation with V

DRIVE

function. The V

DRIVE

function allows the parallel interface to connect directly to

3 V, or 5 V processor systems independent of V

No pipeline delay.

Accurate control of the sampling instant via a CONVST

input and once off conversion control.

Rev.

PrN

Information furnished by Analog Devices is believed to be accurate and reliable.

However, no responsibility is assumed by Analog Devices for its use, nor for any

infringements of patents or other rights of third parties that may result from its use.

Specifications subject to change without notice. No license is granted by implication

or otherwise under any patent or patent rights of Analog Devices. Trademarks and

registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781.329.4700

www.analog.com

Fax: 781.326.8703

03715-0-001

AD7938/AD7939

TABLE OF CONTENTS

AD7938—Specifications.................................................................. 3

AD7939—Specifications.................................................................. 5

Timing Specifications....................................................................... 7

Absolute Maximum Ratings............................................................ 8

ESD Caution.................................................................................. 8

Pin Function Description ................................................................ 9

Terminology .................................................................................... 11

Typical Performance Characteristics ........................................... 13

On-Chip Registers .......................................................................... 16

Circuit Information ........................................................................ 18

Converter Operation.................................................................. 18

ADC Transfer Function............................................................. 18

Typical Connection Diagram ................................................... 19

Analog Input Structure.............................................................. 19

Preliminary Technical Data

Analog Inputs.............................................................................. 20

Analog Input Selection .............................................................. 22

Reference Section ....................................................................... 23

Parallel Interface......................................................................... 25

Power Modes of Operation....................................................... 28

Power vs. Throughput Rate....................................................... 29

Microprocessor Interfacing....................................................... 29

Application Hints ........................................................................... 31

Grounding and Layout .............................................................. 31

PCB Design Guidelines for Chip Scale Package .................... 31

Evaluating the AD7938/AD7939 Performance ...................... 31

Outline Dimensions ....................................................................... 32

Ordering Guide .......................................................................... 32

REVISION HISTORY

8/04—Revision PrN: Preliminary Version

Rev. PrN | Page 2 of 32

AD7938 Related Products

	AD7938	AD7938BCP	AD7938BSU	AD7939	AD7939BCP	AD7939BSU
Description	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer	8-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer

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