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AD7866

Dual 1 MSPS, 12-Bit, 2-Channel

SAR ADC with Serial Interface

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

On-Board Reference 2.5 V

–40 C to +125 C Operation

Flexible Power/Throughput Rate Management

Simultaneous Conversion/Read

No Pipeline Delays

MICROWIRE

Shutdown Mode: 1

A Max

20-Lead TSSOP Package

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

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-and-hold amplifier that 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; 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

twos complement output coding. The AD7866 has an on-chip

2.5 V reference that 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 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 conver-

sion 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.