a

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© Analog Devices, Inc., 2002

REV. 0

AD7904/AD7914/AD7924

4-Channel, 1 MSPS, 8-/10-/12-Bit ADCs

with Sequencer in 16-Lead TSSOP

FUNCTIONAL BLOCK DIAGRAM

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T/H

I/P

MUX

SEQUENCER

CONTROL LOGIC

8-/10-/12-BIT

SUCCESSIVE

APPROXIMATION

ADC

GND

SCLK

DOUT

DIN

CS

AD7904/AD7914/AD7924

FEATURES

Fast Throughput Rate: 1 MSPS

Low Power:

6 mW max at 1 MSPS with 3 V Supplies

13.5 mW max at 1 MSPS with 5 V Supplies

4 (Single-Ended) Inputs with Sequencer

Wide Input Bandwidth:

AD7924, 70 dB SNR at 50 kHz Input Frequency

Flexible Power/Serial Clock Speed Management

No Pipeline Delays

High Speed Serial Interface SPI

Shutdown Mode: 0.5 A Max

16-Lead TSSOP Package

GENERAL DESCRIPTION

The AD7904/AD7914/AD7924 are respectively, 8-bit, 10-bit,

and 12-bit, high speed, low power, 4-channel, successive-approxi-

mation 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 8 MHz.

The conversion process and data acquisition are controlled

using

CS and the serial clock signal, allowing the device to

easily 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 pipeline delays associated

with the part.

The AD7904/AD7914/AD7924 use advanced design techniques to

achieve very low power dissipation at maximum throughput rates.

At maximum throughput rates, the AD7904/AD7914/AD7924

consume 2 mA maximum with 3 V supplies; with 5 V supplies, the

current consumption is 2.7 mA maximum.

Through the configuration of the Control Register, the analog

to 2

output coding. The AD7904/AD7914/AD7924 each feature four

single-ended analog inputs with a channel sequencer to allow a

preprogrammed selection of channels to be converted sequentially.

The conversion time for the AD7904/AD7914/AD7924 is deter-

mined by the SCLK frequency, as this is also used as the master

clock to control the conversion.

PRODUCT HIGHLIGHTS

1. High Throughput with Low Power Consumption.

The AD7904/AD7914/AD7924 offer up to 1 MSPS through-

put rates. At the maximum throughput rate with 3 V sup`plies,

the AD7904/AD7914/AD7924 dissipate just 6 mW of

power maximum.

2. Four Single-Ended Inputs with a Channel Sequencer.

A consecutive sequence of channels can be selected, through

which the ADC will cycle and convert on.

The AD7904/AD7914/AD7924 operate from a single 2.7 V

face to connect directly to either 3 V or 5 V processor systems

4. Flexible Power/Serial Clock Speed Management.

The conversion rate is determined by the serial clock, allowing

the conversion time to be reduced through the serial clock speed

increase. The parts also feature various shutdown modes to

maximize power efficiency at lower throughput rates. Current

consumption is 0.5

µA max when in full shutdown.

5. No Pipeline Delay.

The parts feature a standard successive-approximation ADC

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.