16-Bit, 4-Channel/8-Channel,

250 kSPS PulSAR ADC

Data Sheet

AD7682/AD7689

Rev. D

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FEATURES

16-bit resolution with no missing codes

4-channel (AD7682)/8-channel (AD7689) multiplexer with

choice of inputs

Unipolar single-ended

Differential (GND sense)

Pseudobipolar

Throughput: 250 kSPS

INL: ±0.4 LSB typical, ±1.5 LSB maximum (±23 ppm or FSR)

Dynamic range: 93.8 dB

SINAD: 92.5 dB at 20 kHz

THD: −100 dB at 20 kHz

Multiple reference types

Internal selectable 2.5 V or 4.096 V

External buffered (up to 4.096 V)

External (up to VDD)

Internal temperature sensor (TEMP)

Channel sequencer, selectable 1-pole filter, busy indicator

No pipeline delay, SAR architecture

Single-supply 2.3 V to 5.5 V operation with

1.8 V to 5.5 V logic interface

Serial interface compatible with SPI, MICROWIRE,

QSPI, and DSP

Power dissipation

3.5 mW @ 2.5 V/200 kSPS

12.5 mW @ 5 V/250 kSPS

Standby current: 50 nA

Low cost grade available

20-lead 4 mm × 4 mm LFCSP package

APPLICATIONS

Multichannel system monitoring

Battery-powered equipment

Medical instruments: ECG/EKG

Mobile communications: GPS

Power line monitoring

Data acquisition

Seismic data acquisition systems

Instrumentation

Process control

FUNCTIONAL BLOCK DIAGRAM

AD7689

REF

GND

VDD

VIO

DIN

SCK

SDO

CNV

1.8V

TO

VDD

2.3V TO 5.5V

SEQUENCER

SPI SERIAL

INTERFACE

MUX

16-BIT SAR

ADC

BAND GAP

REF

TEMP

SENSOR

REFIN

IN0

IN1

IN4

IN5

IN6

IN7

IN3

IN2

COM

0.5V TO VDD

10µF

ONE-POLE

LPF

0.5V TO VDD – 0.5V

0.1µF

Figure 1.

Table 1. Multichannel 14-/16-Bit PulSAR® ADC

Type

Channels

250 kSPS

500 kSPS

ADC Driver

14-Bit

8

AD7949

ADA4841-x

16-Bit

4

AD7682

ADA4841-x

16-Bit

8

AD7689

AD7699

ADA4841-x

GENERAL DESCRIPTION

The AD7682/AD7689 are 4-channel/8-channel, 16-bit, charge

redistribution successive approximation register (SAR) analog-

to-digital converters (ADCs) that operate from a single power

supply, VDD.

The AD7682/AD7689 contain all components for use in a

multichannel, low power data acquisition system, including a

true 16-bit SAR ADC with no missing codes; a 4-channel

(AD7682) or 8-channel (AD7689), low crosstalk multiplexer

that is useful for configuring the inputs as single-ended (with or

without ground sense), differential, or bipolar; an internal low

drift reference (selectable 2.5 V or 4.096 V) and buffer; a

temperature sensor; a selectable one-pole filter; and a sequencer

that is useful when channels are continuously scanned in order.

The AD7682/AD7689 use a simple SPI interface for writing to

the configuration register and receiving conversion results. The

SPI interface uses a separate supply, VIO, which is set to the

host logic level. Power dissipation scales with throughput.

The AD7682/AD7689 are housed in a tiny 20-lead LFCSP with

operation specified from −40°C to +85°C.