24-Bit, 312 kSPS, 109 dB Sigma-Delta ADC

with On-Chip Buffers and Serial Interface

Data Sheet

AD7764

Rev. B

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FEATURES

High performance 24-bit ∑-∆ ADC

115 dB dynamic range at 78.125 kHz output data rate

109 dB dynamic range at 312.5 kHz output data rate

312.5 kHz maximum fully filtered output word rate

Pin-selectable oversampling rates of 64×, 128×, and 256×

Low power mode

Flexible serial peripheral interface (SPI)

Fully differential modulator input

On-chip differential amplifier for signal buffering

On-chip reference buffer

Full band, low-pass, finite impulse response (FIR) filter

Overrange alert pin

Digital gain correction registers

Power-down mode

Synchronization of multiple devices via the SYNC pin

Daisy chaining

APPLICATIONS

Data acquisition systems

Vibration analysis

Instrumentation

FUNCTIONAL BLOCK DIAGRAM

REFGND

BUF

GND

MCLK

OVERRANGE

DEC_RATE

SYNC

RESET/PWRDWN

FSO SCO

SDI

SDO

FSI

DIFF

MULTIBIT

Σ-Δ

MODULATOR

RECONSTRUCTION

DECIMATION

FIR FILTER ENGINE

AD7764

INTERFACE LOGIC AND

OFFSET AND GAIN

CORRECTION REGISTERS

Figure 1.

Table 1. Related Devices

Device No.

Description

AD7760

2.5 MSPS, 100 dB, parallel output, on-chip buffer

AD7762

625 kSPS, 109 dB, parallel output, on-chip buffer

AD7763

625 kSPS, 109 dB, serial output, on-chip buffers

AD7765

156 kSPS, 112 dB, serial output, on-chip buffers

AD7766

128/64/32 kSPS, 8.5 mW, 109 dB SNR

AD7767

128/64/32 kSPS, 8.5 mW, 109 dB SNR

GENERAL DESCRIPTION

The AD7764 is a high performance, 24-bit, sigma-delta (Σ-Δ)

analog-to-digital converter (ADC). It combines wide input band-

width, high speed, and performance of 109 dB dynamic range at a

312.5 kHz output data rate. With excellent dc specifications, the

converter is ideal for high speed data acquisition of ac signals

where dc data is also required.

Using the AD7764 eases front-end antialias filtering requirements,

simplifying the design process significantly. The AD7764 offers

pin-selectable decimation rates of 64×, 128×, and 256×. Other

features include an integrated buffer to drive the reference, as

well as a fully differential amplifier to buffer and level shift the

input to the modulator.

An overrange alert pin indicates when an input signal exceeds

the acceptable range. The addition of internal gain and internal

overrange registers makes the AD7764 a compact, highly

integrated data acquisition device requiring minimal peripheral

components.

The AD7764 also offers a low power mode, significantly

reducing power dissipation without reducing the output data

rate or available input bandwidth.

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 external clock frequency applied to the

AD7764 determines the sample rate, filter corner frequencies,

and output word rate.

The AD7764 device boasts a full band, on-board FIR filter. The

full stop-band attenuation of the filter is achieved at the Nyquist

frequency. This feature offers increased protection from signals

that lie above the Nyquist frequency being aliased back into the

input signal bandwidth.

The reference voltage supplied to the AD7764 determines the

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

±3.2768 V differential, biased around a common mode of

2.048 V. This common-mode biasing is achieved using the

on-chip differential amplifier, further reducing the external

signal conditioning requirements.

The AD7764 is available in a 28-lead TSSOP package and is

specified over the industrial temperature range of −40°C

to +85°C.