18-Bit, 250 kSPS, Differential

AD7631

Rev. A

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FEATURES

Multiple pins/software-programmable input ranges

+5 V (10 V p-p), +10 V (20 V p-p), ±5 V (20 V p-p),

±10 V (40 V p-p)

Pins or serial SPI-compatible input ranges/mode selection

Throughput: 250 kSPS

INL: ±1.5 LSB typical, ±2.5 LSB maximum (±9.5 ppm of FSR)

18-bit resolution with no missing codes

Dynamic range: 102.5 dB

SNR: 101 dB @ 2 kHz

THD: −112 dB @ 2 kHz

iCMOS® process technology

5 V internal reference: typical drift 3 ppm/°C; TEMP output

No pipeline delay (SAR architecture)

Parallel (18-/16-/8-bit bus) and serial 5 V/3.3 V interface

SPI-/QSPI™-/MICROWIRE™-/DSP-compatible

Power dissipation

73 mW @ 250 kSPS

10 mW @ 1 kSPS

Pb-free, 48-lead LQFP and 48-lead LFCSP (7 mm × 7 mm)

APPLICATIONS

Process controls

High speed data acquisition

Digital signal processing

Spectrum analysis

ATE

GENERAL DESCRIPTION

The AD7631 is an 18-bit, charge redistribution, successive

approximation register (SAR), architecture analog-to-digital

converter (ADC) fabricated on Analog Devices, Inc.’s iCMOS

high voltage process. The device is configured through hardware

or via a dedicated write-only serial configuration port for input

range and operating mode. The AD7631 contains a high speed

18-bit sampling ADC, an internal conversion clock, an internal

reference (and buffer), error correction circuits, and both serial

and parallel system interface ports. A falling edge on CNVST

samples the fully differential analog inputs on IN+ and IN−.

The AD7631 features four different analog input ranges. Power is

scaled linearly with throughput. Operation is specified from

−40°C to +85°C.

FUNCTIONAL BLOCK DIAGRAM

18

CONTROL LOGIC AND

CALIBRATION CIRCUITRY

CLOCK

AD7631

DGND

DVDD

AVDD

AGND

REF REFGND

IN+

PD

RESET

CNVST

PDBUF

REFBUFIN

PDREF

REF

TEMP

D[17:0]

BUSY

RD

CS

D0/OB/2C

OGND

OVDD

D2/A1

D1/A0

REF

AMP

SERIAL DATA

PORT

PARALLEL

INTERFACE

SWITCHED

CAP DAC

VCC VEE

BIPOLAR TEN

SERIAL

CONFIGURATION

PORT

IN–

MODE0

MODE1

Figure 1.

Table 1. 48-Lead PulSAR Selection

Input Type

Res

(Bits)

100 to

250

(kSPS)

500 to

570

(kSPS)

570 to

1000

(kSPS)

>1000

(kSPS)

Bipolar

14

AD7951

Differential

Bipolar

14

AD7952

Unipolar

16

AD7651

AD7650

AD7653

AD7660

AD7652

AD7667

AD7661

AD7664

AD7666

Bipolar

16

AD7610

AD7665

AD7612

AD7663

AD7671

Differential

16

AD7675

AD7676

AD7677

AD7621

Unipolar

AD7622

AD7623

Simultaneous/

16

AD7654

Multichannel

Unipolar

AD7655

Differential

18

AD7678

AD7679

AD7674

AD7641

Unipolar

AD7643

Differential

Bipolar

18

AD7631

AD7634