REV. B

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a

AD7724

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Dual CMOS - Modulators

FUNCTIONAL BLOCK DIAGRAM

AVIN(+)

AVIN(–)

BVIN(+)

BVIN(–)

MZERO

GC

BIP

STBY

RESET

DVDD

DVDD1

DGND

AVDD

AGND

ADATA

SCLK

BDATA

XTAL OFF

XTAL1

XTAL2/MCLK

DVAL

REF1 REF2A

REF2B

CLOCK

CIRCUITRY

AD7724

2.5V

REFERENCE

-

MODULATOR A

-

MODULATOR B

CONTROL

LOGIC

FEATURES

13 MHz Master Clock Frequency

0 V to +2.5 V or

1.25 V Input Range

Single Bit Output Stream

90 dB Dynamic Range

Power Supplies

AVDD, DVDD: 5 V

5%

DVDD1: 3 V

5%

Logic Outputs 3 V/5 V Compatible

On-Chip 2.5 V Voltage Reference

48-Lead LQFP

GENERAL DESCRIPTION

This device consists of two seventh order sigma-delta modula-

tors. Each modulator converts its analog input signal into a high

speed 1-bit data stream. The part operates from a 5 V power

supply and accepts a differential input range of 0 V to +2.5 V or

±1.25 V centered about a common-mode bias. The analog inputs

are continuously sampled by the analog modulators, eliminating

the need for external sample-and-hold circuitry. The input

information is contained in the output stream as a density of

ones. The original information can be digitally reconstructed

with an appropriate digital filter.

The part provides an accurate on-chip 2.5 V reference for each

modulator. A reference input/output function is provided to

allow either the internal reference or an external system refer-

ence to be used as the reference source for the modulator.

The device is offered in a 48-lead LQFP package and designed

to operate from –40

°C to +85°C.