Differential ADC in MSOP/QFN

AD7691

Rev. 0

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FEATURES

18-bit resolution with no missing codes

Throughput: 250 kSPS

INL: ±0.75 LSB typ, ±1.5 LSB max (±6 ppm of FSR)

Dynamic range: 102 dB typ @ 250 kSPS

Oversampled dynamic range: 125 dB @1 kSPS

Noise-free code resolution: 20 bits @ 1 kSPS

Effective resolution: 22.7 bits @ 1 kSPS

SINAD: 101.5 dB typ @ 1 kHz

THD: −125 dB typ @ 1 kHz

No pipeline delay

Single-supply 2.3 V to 5 V operation with

1.8 V/2.5 V/3 V/5 V logic interface

Serial interface SPI®/QSPI™/MICROWIRE™/DSP compatible

Daisy-chain multiple ADCs and busy indicator

Power dissipation

5 mW @ 5 V/250 kSPS

50 μW @ 5 V/1 kSPS

Standby current: 1 nA

10-lead package: MSOP (MSOP-8 size) and

3 mm × 3 mm QFN1 (LFCSP) (SOT-23 size)

Pin-for-pin compatible with the18-bit AD7690 and 16-bit

AD7693, AD7688, and AD7687

APPLICATIONS

Battery-powered equipment

Data acquisitions

Seismic data acquisition systems

DVMs

Instrumentation

Medical instruments

1.5

–1.5

0

262144

CODE

1.0

0.5

0

–0.5

–1.0

65536

131072

196608

POSITIVE INL = 0.43LSB

NEGATIVE INL = –0.62LSB

Figure 1. Integral Nonlinearity vs. Code, 5 V

APPLICATION DIAGRAM

AD7691

REF

GND

VDD

IN+

IN–

VIO

SDI

SCK

SDO

CNV

+1.8V TO VDD

3- OR 4-WIRE

INTERFACE

(SPI, DAISY CHAIN, CS)

+2.3V TO VDD

±10V, ±5V, ...

+2.3V TO +5V

ADA4941

Figure 2.

Table 1. MSOP, QFN1 (LFCSP)/SOT-23

14-/16-/18-Bit PulSAR ADC

Type

100

kSPS

250

kSPS

400 kSPS

to

500 kSPS

ADC

Driver

18-Bit

AD7691

AD7690

ADA4941-1

ADA4841-x

16-Bit True

Differential

AD7684

AD7687

AD7688

AD7693

ADA4941-1

ADA4841-x

16-Bit Pseudo

AD7683

AD7685

AD7686

ADA4841-x

Differential/

Unipolar

AD7680

AD7694

14-Bit

AD7940

AD7942

AD7946

ADA4841-x

GENERAL DESCRIPTION

The AD7691 is an 18-bit, charge redistribution, successive

approximation, analog-to-digital converter (ADC) that operates

from a single power supply, VDD, between 2.3 V and 5 V. It

contains a low power, high speed, 18-bit sampling ADC with no

missing codes, an internal conversion clock, and a versatile

serial interface port. On the CNV rising edge, it samples the

voltage difference between the IN+ and IN− pins. The voltages

on these pins usually swing in opposite phase between 0 V and

REF. The reference voltage, REF, is applied externally and can

be set up to the supply voltage.

Its power scales linearly with throughput.

The SPI-compatible serial interface also features the ability,

using the SDI input, to daisy-chain several ADCs on a single

3-wire bus and provides an optional busy indicator. It is compatible

with 1.8 V, 2.5 V, 3 V, or 5 V logic, using the separate VIO supply.

The AD7691 is housed in a 10-lead MSOP or a 10-lead QFN1

(LFCSP) with operation specified from −40°C to +85°C.