625 kSPS, 24-Bit, 109 dB Sigma-Delta ADC

With On-Chip Buffer

Data Sheet

AD7762

Rev. A

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FEATURES

120 dB dynamic range at 78 kHz output data rate

109 dB dynamic range at 625 kHz output data rate

112 dB SNR at 78 kHz output data rate

106 dB SNR at 625 kHz output data rate

625 kHz maximum fully filtered output word rate

Programmable over-sampling rate (32× to 256×)

Fully differential modulator input

On-chip differential amplifier for signal buffering

Low-pass finite impulse response (FIR) filter with default or

user-programmable coefficients

Overrange alert bit

Digital offset and gain correction registers

Filter bypass modes

Low power and power-down modes

Synchronization of multiple devices via SYNC pin

APPLICATIONS

Data acquisition systems

Vibration analysis

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

AD7762

AGND

MCLK

DGND

DECAPA/B

SYNC

RESET

DB0 TO DB15

CS

DRDY

RD/WR

CONTROL LOGIC

I/O

OFFSET AND GAIN

REGISTERS

DIFF

MULTIBIT

Σ-∆

MODULATOR

RECONSTRUCTION

FIR FILTER

ENGINE

PROGRAMMABLE

DECIMATION

BUF

Figure 1.

GENERAL DESCRIPTION

The AD7762 is a high performance, 24-bit Σ-Δ analog-to-

digital converter (ADC). It combines wide input bandwidth

and high speed with the benefits of Σ-Δ conversion with a

performance of 106 dB SNR at 625 kSPS, making it ideal for

high speed data acquisition. Wide dynamic range combined

with significantly reduced antialiasing requirements simplify

the design process. An integrated buffer to drive the reference,

a differential amplifier for signal buffering and level shifting, an

overrange flag, internal gain and offset registers, and a low-pass

digital FIR filter make the AD7762 a compact, highly integrated

data acquisition device requiring minimal peripheral com-

ponent selection. In addition, the device offers programmable

decimation rates, and the digital FIR filter can be adjusted if

the default characteristics are not appropriate to the application.

The AD7762 is ideal for applications demanding high SNR

without a complex front end signal processing design.

The differential input is sampled at up to 40 MSPS by an analog

modulator. The modulator output is processed by a series of low-

pass filters, the final filter having default or user-programmable

coefficients. The sample rate, filter corner frequencies, and output

word rate are set by a combination of the external clock frequency

and the configuration registers of the AD7762.

The reference voltage supplied to the AD7762 determines the

analog input range. With a 4 V reference, the analog input range

is ±3.2 V differential biased around a common mode of 2 V.

This common-mode biasing can be achieved using the on-chip

differential amplifier, further reducing the external signal

conditioning requirements.

The AD7762 is available in an exposed paddle, 64-lead TQFP

and is specified over the industrial temperature range from

−40°C to +85°C.

Table 1. Related Devices

Part No.

Description

AD7760

24-bit, 2.5 MSPS, 100 dB Σ-Δ, parallel interface

AD7763

24-bit, 625 kSPS, 109 dB Σ-Δ, serial interface