16-Bit, 1.5 LSB INL, 500 kSPS PulSAR™

Differential ADC in MSOP/LFCSP

Data Sheet

AD7688

FEATURES

16-bit resolution with no missing codes

Throughput: 500 kSPS

INL: ±0.4 LSB typ, ±1.5 LSB max (±23 ppm of FSR)

Dynamic range: 96.5 dB

SNR: 95.5 dB at 20 kHz

THD: −118 dB at 20 kHz

True differential analog input range

No pipeline delay

Single-supply 5 V operation with

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

Proprietary serial interface

SPI®/QSPI™/MICROWIRE™/DSP-compatible1

Daisy-chain multiple ADCs and BUSY indicator

Power dissipation

3.75 mW at 5 V/100 kSPS

3.75 µW at 5 V/100 SPS

Standby current: 1 nA

10-lead MSOP (MSOP-8 size) and

3 mm × 3 mm LFCSP (SOT-23 size)

Pin-for-pin compatible with AD7685, AD7686, and AD7687

APPLICATIONS

Battery-powered equipment

Data acquisitions

Instrumentation

Medical instruments

Process controls

CODE

1.5

1.0

0.5

0

–0.5

–1.0

–1.5

0

16384

32768

49152

65535

POSITIVE INL = +0.31LSB

NEGATIVE INL = –0.39LSB

Figure 1. Integral Nonlinearity vs. Code

APPLICATION DIAGRAM

AD7688

REF

GND

VDD

IN+

IN–

VIO

SDI

SCK

SDO

CNV

1.8V TO VDD

3- OR 4-WIRE INTERFACE

(SPI, DAISY CHAIN, CS)

0.5V TO 5V

5V

VREF

0

VREF

0

Figure 2.

Table 1. MSOP, LFCSP/SOT-23 16-Bit PulSAR ADC

Type

100 kSPS

250 kSPS

500 kSPS

True Differential

AD7684

AD7687

AD7688

Pseudo

AD7683

AD7685

AD7686

Differential/Unipolar

AD7694

Unipolar

AD7680

GENERAL DESCRIPTION

The AD7688 is a 16-bit, charge redistribution, successive

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

from a single 5 V power supply, VDD. It contains a low power,

high speed, 16-bit sampling ADC with no missing codes, an

internal conversion clock, and a versatile serial interface port.

The part also contains a low noise, wide bandwidth, short

aperture delay track-and-hold circuit. On the CNV rising edge,

it samples the voltage difference between 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

supply VIO.

The AD7688 is housed in a 10-lead MSOP or a 10-lead LFCSP

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

1

Protected by U.S. Patent 6,703,961.

Rev. B

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