REV. 0

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a

AD7866

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., 2002

Dual 1 MSPS, 12-Bit, 2-Channel

SAR ADC with Serial Interface

FUNCTIONAL BLOCK DIAGRAM

DGND

REF SELECT

A0

12-BIT

SUCCESSIVE-

APPROXIMATION

ADC

AD7866

2.5V

REF

T/H

MUX

BUF

OUTPUT

DRIVERS

RANGE

SCLK

CS

CONTROL

LOGIC

12-BIT

SUCCESSIVE-

APPROXIMATION

ADC

T/H

MUX

OUTPUT

DRIVERS

BUF

AGND

AGND

FEATURES

Dual 12-Bit, 2-Channel ADC

Fast Throughput Rate

1 MSPS

Low Power

11.4 mW Max at 1 MSPS with 3 V Supplies

24 mW Max at 1 MSPS with 5 V Supplies

Wide Input Bandwidth

70 dB SNR at 300 kHz Input Frequency

Onboard Reference 2.5 V

Flexible Power/Throughput Rate Management

Simultaneous Conversion/Read

No Pipeline Delays

Shut-Down Mode

1

A Max

20-Lead TSSOP Package

GENERAL DESCRIPTION

The AD7866 is a dual 12-bit high-speed, low power, successive-

approximation ADC. The part operates from a single 2.7 V to 5.25 V

power supply and features throughput rates up to 1 MSPS. The

device contains two ADCs, each preceded by a low-noise, wide

bandwidth track/hold amplifier which can handle input frequencies

in excess of 10 MHz.

The conversion process and data acquisition are controlled

using standard control inputs allowing easy interfacing to

microprocessors or DSPs. The input signal is sampled on the

falling edge of

CS and conversion is also initiated at this point.

The conversion time is determined by the SCLK frequency.

There are no pipelined delays associated with the part.

The AD7866 uses advanced design techniques to achieve very low

power dissipation at high throughput rates. With 3 V supplies

and 1 MSPS throughput rate, the part consumes a maximum of

3.8 mA. With 5 V supplies and 1 MSPS, the current consumption

is a maximum of 4.8 mA. The part also offers flexible power/

throughput rate management when operating in sleep mode.

The analog input range for the part can be selected to be a 0 V

two’s complement output coding. The AD7866 has an

on-chip 2.5 V reference which can be overdriven if an external

reference is preferred. Each on-board ADC can also be supplied

with a separate individual external reference.

The AD7866 is available in a 20-lead thin shrink small outline

(TSSOP) package.

PRODUCT HIGHLIGHTS

1. The AD7866 features two complete ADC functions allowing

simultaneous sampling and conversion of two channels. Each

ADC has a 2-channel input multiplexer. The conversion

result of both channels is available simultaneously on separate

data lines, or both may be taken on one data line if only one

serial port is available.

2. High Throughput with Low Power Consumption—The

AD7866 offers a 1 MSPS throughput rate with 11.4 mW

maximum power consumption when operating at 3 V.

3. Flexible Power/Throughput Rate Management—The

conversion rate is determined by the serial clock allowing

the power consumption to be reduced as the conversion time

is reduced through a SCLK frequency increase. Power

efficiency can be maximized at lower throughput rates if the

part enters sleep during conversions.

4. No Pipeline Delay—The part features two standard successive-

approximation ADCs with accurate control of the sampling

instant via a

CS input and once off conversion control.

SPI and QSPI are trademarks of Motorola Inc.

MICROWIRE is a trademark of National Semiconductor Corporation.