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

with Sequencer in 20-Lead TSSOP

Data Sheet

AD7908/AD7918/AD7928

Rev. E

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FEATURES

Fast throughput rate: 1 MSPS

Low power

6.0 mW max at 1 MSPS with 3 V supply

13.5 mW max at 1 MSPS with 5 V supply

Eight (single-ended) inputs with sequencer

Wide input bandwidth

AD7928, 70 dB min SINAD at 50 kHz input frequency

Flexible power/serial clock speed management

No pipeline delays

High speed serial interface SPI®/QSPI™/

MICROWIRE™/DSP compatible

Shutdown mode: 0.5 μA max

20-lead TSSOP package

Qualified for automotive applications

GENERAL DESCRIPTION

The AD7908/AD7918/AD7928 are, respectively, 8-bit, 10-bit, and

12-bit, high speed, low power, 8-channel, 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-and-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 AD7908/AD7918/AD7928 use advanced design techniques to

achieve very low power dissipation at maximum throughput rates.

At maximum throughput rates, the AD7908/AD7918/AD7928

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 input

coding. The AD7908/AD7918/AD7928 each feature eight single-

ended analog inputs with a channel sequencer to allow a

preprogrammed selection of channels to be converted sequentially.

The conversion time for the AD7908/AD7918/AD7928 is

determined by the SCLK frequency, which is also used as the

master clock to control the conversion.

FUNCTIONAL BLOCK DIAGRAM

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T/H

I/P

MUX

SEQUENCER

CONTROL LOGIC

GND

SCLK

DOUT

DIN

CS

AD7908/AD7918/AD7928

8-/10-/12-BIT

SUCCESSIVE

APPROXIMATION

ADC

Figure 1.

PRODUCT HIGHLIGHTS

1. High Throughput with Low Power Consumption. The AD7908/

AD7918/AD7928 offer up to 1 MSPS throughput rates. At the

maximum throughput rate with 3 V supplies, the AD7908/

AD7918/AD7928 dissipate just 6 mW of power maximum.

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

A sequence of channels can be selected, through which

the ADC cycles and converts on.

AD7918/AD7928 operate from a single 2.7 V to 5.25 V supply.

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.