14-Bit, 8-Channel,

250 kSPS PulSAR ADC

AD7949

Rev. B

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FEATURES

14-bit resolution with no missing codes

8-channel multiplexer with choice of inputs

Unipolar single-ended

Differential (GND sense)

Pseudobipolar

Throughput: 250 kSPS

INL/DNL: ±0.5/±0.25 LSB typical

SINAD: 85 dB @ 20 kHz

THD: −100 dB @ 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

2.9 mW @ 2.5 V/200 kSPS

10.8 mW @ 5 V/250 kSPS

Standby current: 50 nA

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

AD7949

REF

GND

VDD

VIO

DIN

SCK

SDO

CNV

1.8V

TO

VDD

2.3V TO 5.5V

SEQUENCER

SPI SERIAL

INTERFACE

MUX

14-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® ADCs

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 AD7949 is an 8-channel, 14-bit, charge redistribution

successive approximation register (SAR) analog-to-digital

converter (ADC) that operates from a single power supply, VDD.

The AD7949 contains all components for use in a multichannel,

low power data acquisition system, including a true 14-bit SAR

ADC with no missing codes; an 8-channel, 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 AD7949 uses 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 AD7949 is housed in a tiny 20-lead LFCSP with operation

specified from −40°C to +85°C.