2.5 MSPS, 20-Bit

Σ∆ ADC

Preliminary Technical Data

AD7760

Rev. PrN

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FEATURES

High performance 20-bit Sigma-Delta ADC

118dB SNR at 78kHz output data rate

100dB SNR at 2.5MHz output data rate

2.5 MHz maximum fully filtered output word rate

Programmable over-sampling rate (8x to 256x)

Flexible parallel interface

Fully differential modulator input

On-chip differential amplifier for signal buffering

Low pass FIR filter with default or user programmable

coefficients

Over-range 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

DIFF

Multi-Bit

Sigma-Delta

Modulator

AD7760

Control Logic,

I/O and

Registers

Reconstruction

Programmable

Decimation

FIR Filter

Engine

DB0 - DB15

VIN+

VIN-

AVDD1

AGND

VREF+

MCLK

DGND

BUF

VDRIVE

MCLK

SYNC

RESET

AVDD2

AVDD3

AVDD4

DVDD

-

+

DECAP

RBIAS

Figure 1.

PRODUCT OVERVIEW

The AD7760 high performance 20-bit sigma delta analog to

digital converter combines wide input bandwidth and high

speed with the benefits of sigma delta conversion with

performance of 100dB SNR at 2.5MSPS making it ideal for high

speed data acquisition. Wide dynamic range combined with

significantly reduced anti-aliasing requirements simplify the

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

differential amplifier for signal buffering and level shifting, an

over-range flag, internal gain & offset registers and a low-pass

digital FIR filter make the AD7760 a compact highly integrated

data acquisition device requiring minimal peripheral

component 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 AD7760 is ideal for applications demanding

high SNR without necessitating design of complex front end

signal processing.

The differential input is sampled at up to 40MS/s by an analog

modulator. The modulator output is processed by a series of

low-pass filters, the final one 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 AD7760.

The reference voltage supplied to the AD7760 determines the

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

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

common mode biasing can be achieved using the on-chip

differential amplifiers, further reducing the external signal

conditioning requirements.

The AD7760 is available in an exposed paddle 64-lead TQFP

and 48-lead CSP packages and is specified over the industrial

temperature range from -40°C to +85°C.