a

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© Analog Devices, Inc., 2002

REV. A

AD7490

16-Channel, 1 MSPS, 12-Bit ADC

with Sequencer in 28-Lead TSSOP

FUNCTIONAL BLOCK DIAGRAM

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T/H

I/P

MUX

SEQUENCER

CONTROL LOGIC

12-BIT

SUCCESSIVE

APPROXIMATION

ADC

GND

SCLK

DOUT

DIN

CS

AD7490

FEATURES

Fast Throughput Rate: 1 MSPS

Low Power at Max Throughput Rates:

5.4 mW Max at 870 kSPS with 3 V Supplies

12.5 mW Max at 1 MSPS with 5 V Supplies

16 (Single-Ended) Inputs with Sequencer

Wide Input Bandwidth:

69.5 dB SNR at 50 kHz Input Frequency

Flexible Power/Serial Clock Speed Management

No Pipeline Delays

High Speed Serial Interface SPI™/QSPI™/

MICROWIRE™/DSP Compatible

Full Shutdown Mode: 0.5

A Max

28-Lead TSSOP and 32-Lead LFCSP Packages

GENERAL DESCRIPTION

The AD7490 is a 12-bit high speed, low power, 16-channel,

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 part contains a low noise, wide bandwidth

track-and-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 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 AD7490 uses advanced design techniques to achieve very

low power dissipation at high throughput rates. For maximum

throughput rates, the AD7490 consumes just 1.8 mA with 3 V

supplies, and 2.5 mA with 5 V supplies.

By setting the relevant bits in the Control Register, the analog

a 0 to 2

output coding. The AD7490 features 16 single-ended analog

inputs with a channel sequencer to allow a preprogrammed

selection of channels to be converted sequentially.

The conversion time is determined by the SCLK frequency as

this is also used as the master clock to control the conversion.

The AD7490 is available in a 28-lead thin shrink small outline

(TSSOP) package, and a 32-lead chip scale package.

SPI and QSPI are trademarks of Motorola Inc.

MICROWIRE is a trademark of National Semiconductor Corporation

PRODUCT HIGHLIGHTS

1. High Throughput with Low Power Consumption

The AD7490 offers up to 1 MSPS throughput rates. At

maximum throughput with 3 V supplies, the AD7490

dissipates just 5.4 mW of power.

2. Sixteen Single-Ended Inputs with Channel Sequencer

A Sequence of channels can be selected, through which the

AD7490 will cycle and convert.

The AD7490 operates from a single 2.7 V to 5.25 V supply.

directly to either 3 V or 5 V processor systems independent

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 part also features various shutdown

modes to maximize power efficiency at lower throughput

rates. Power consumption is 0.5

µA max when in full shutdown.

5. 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.