REV. PrC

7/13/01

PreliminaryTechnicalData

PRELIMINARY TECHNICAL DATA

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

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

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AD7484

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

Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2001

3MSPS,

14-Bit SAR ADC

FUNCTIONAL BLOCK DIAGRAM

FEATURES

Fast Throughput Rate: 3Msps

Wide Input Bandwidth: 50MHz

No Pipeline Delays with SAR ADC

Excellent DC Accuracy Performance

Two Parallel Interface Modes

Low Power:

90mW (Full-Power) and 5mW (NAP Mode)

Standby Mode: 1µA max

Single +5V Supply Operation

Internal +2.5V Reference

Full-Scale Overrange Mode (using 15th bit)

System Offset Removal via User Access Offset Register

Nominal 0 to +2.5V Input with Shifted Range Capability

Pin Compatible Upgrade of 12-Bit AD7482

GENERAL DESCRIPTION

The AD7484 is a 14-bit, high speed, low power, succes-

sive-approximation ADC. The part features a parallel

interface with throughput rates up to 3Msps. The part

contains a low-noise, wide bandwidth track/hold amplifier

which can handle input frequencies in excess of 50MHz.

The conversion process is a proprietary algorithmic suc-

cessive-approximation technique which results in no

pipeline delays. The input signal is sampled and a conver-

sion is initiated on the falling edge of the

CONVST

signal. The conversion process is controlled via an inter-

nally trimmed oscillator. Interfacing is via standard

parallel signal lines making the part directly compatible

with microcontrollers and DSPs.

The AD7484 provides excellent ac and dc performance

specifications. Factory trimming ensures high dc accuracy

resulting in very low INL, offset and gain errors.

The part uses advanced design techniques to achieve very

low power dissipation at high throughput rates. Power

consumption in normal mode of operation is 90mW.

There are two power-saving modes: a NAP mode, which

keeps the reference circuitry alive for a quick power up

while consuming 5mW and a STANDBY mode which

reduces power consumption to a mere 5µW.

The AD7484 features an on-board +2.5V reference but

the part can also accomodate an externally-provided

+2.5V reference source. The nominal analog input range

is 0 to +2.5V but an offset shift capability allows this

nominal range to be offset by +/-200mV. This allows the

user considerable flexibility in setting the bottom end

reference point of the signal range, a useful feature when

using single-supply op-amps.

The AD7484 also provides the user with an 8% overrange

capability via a 15th bit. Thus, if the analog input range

strays outside the nominal by up to 8%, the user can still

accurately resolve the signal by using the 15th bit.

The AD7484 is powered from a +4.75V to +5.25V sup-

user to set the voltage levels for the digital interface lines.

The part is housed in a 48-pin LQFP package and is

specified over a -40°C to +85°C temperature range.

2.5V

REFERENCE

NAP

MODE2

BUF

T/H

AVDD AGND CBIAS DVDD DGND

VREF3

VREF1

VREF2

VIN

14-Bit Error

Correcting SAR

MODE1

CLIP

STBY

RESET

VDRIVE

CONVST

D14

D13

D12

D11

D10

D9

D8

CONTROL

LOGIC AND I/O

REGISTERS

D7

AD7484