REV. A

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a

AD7475/AD7495

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

© Analog Devices, Inc., 2001

1 MSPS,

12-Bit ADCs

FUNCTIONAL BLOCK DIAGRAMS

T/H

12-BIT

SUCCESSIVE

APPROXIMATION

ADC

AD7475

GND

SCLK

CS

CONTROL

LOGIC

SDATA

REF IN

T/H

12-BIT

SUCCESSIVE

APPROXIMATION

ADC

AD7495

GND

SCLK

CS

CONTROL

LOGIC

SDATA

BUF

2.5V

REFERENCE

REF OUT

PRODUCT HIGHLIGHTS

1. High throughput with low power consumption. The

AD7475 offers 1 MSPS throughput rates with 4.5 mW

power consumption.

AD7495 operate from a single 2.7 V to 5.25 V supply. The

3. Flexible power/serial clock speed management. The con-

version rate is determined by the serial clock, allowing the

conversion time to be reduced through the serial clock speed

increase. The part also features shutdown modes to maximize

power efficiency at lower throughput rates. This allows the

average power consumption to be reduced while not convert-

ing. Power consumption is 1

µA when in full shutdown.

4. No pipeline delay. The part features a standard successive-

approximation ADC with accurate control of the sampling

instant via a

CS input and once off conversion control.

FEATURES

Fast Throughput Rate: 1 MSPS

Low Power:

4.5 mW Max at 1 MSPS with 3 V Supplies

10.5 mW Max at 1 MSPS with 5 V Supplies

Wide Input Bandwidth:

68 dB SNR at 300 kHz Input Frequency

Flexible Power/Serial Clock Speed Management

No Pipeline Delays

High-Speed Serial Interface SPI™/QSPI™/

MICROWIRE™/DSP-Compatible

On-Board Reference 2.5 V (AD7495 Only)

Standby Mode: 1

A Max

8-Lead

SOIC and SOIC Packages

APPLICATIONS

Battery-Powered Systems

Personal Digital Assistants

Medical Instruments

Mobile Communications

Instrumentation and Control Systems

Data Acquisition Systems

High-Speed Modems

Optical Sensors

GENERAL DESCRIPTION

The AD7475/AD7495 are 12-bit high-speed, low-power,

successive-approximation ADCs. The parts operate from a single

2.7 V to 5.25 V power supply and feature throughput rates up to

1 MSPS. The parts contain a low-noise, wide bandwidth track/hold

amplifier that can handle input frequencies in excess of 1 MHz.

The conversion process and data acquisition are controlled using

CS and the serial clock allowing the devices to interface with

microprocessors or DSPs. The input signal is sampled on the

falling edge of

CS and conversion is also initiated at this point.

There are no pipelined delays associated with the part.

The AD7475/AD7495 use advanced design techniques to achieve

very low power dissipation at high throughput rates. With 3 V

supplies and 1 MSPS throughput rate, the AD7475 consumes just

1.5 mA, while the AD7495 consumes 2 mA. With 5 V supplies

and 1 MSPS, the current consumption is 2.1 mA for the AD7475

and 2.6 mA for the AD7495.

The analog input range for the part is 0 V to REF IN. The 2.5 V

reference for the AD7475 is applied externally to the REF IN pin

while the AD7495 has an on-board 2.5 V reference. The conver-

sion time is determined by the SCLK frequency.

MICROWIRE is a trademark of National Semiconductor Corporation.

SPI and QSPI are trademarks of Motorola, Inc.