16-Bit Low Power Sigma-Delta ADC

AD7171

Rev. 0

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FEATURES

Output data rate: 125 Hz

Pin-programmable power-down and reset

Status function

Internal clock oscillator

Current: 135 μA

Power supply: 2.7 V to 5.25 V

–40°C to +105°C temperature range

Package: 10-lead 3 mm x 3 mm LFCSP

INTERFACE

2-wire serial (read-only device)

SPI compatible

Schmitt trigger on SCLK

APPLICATIONS

Weigh scales

Pressure measurement

Industrial process control

Portable instrumentation

FUNCTIONAL BLOCK DIAGRAM

16-BIT Σ-Δ

ADC

AD7171

GND

INTERNAL

CLOCK

REFIN(+)

AIN(+)

AIN(–)

REFIN(–)

DOUT/RDY

SCLK

PDRST

Figure 1.

Table 1.

RMS Noise

P-P Noise

P-P

Resolution

ENOB

5 V

11.5 μV

76 μV

16 bits

16 bits

3 V

6.9 μV

45 μV

16 bits

16 bits

GENERAL DESCRIPTION

The AD7171 is a very low power 16-bit analog-to-digital converter

(ADC). It contains a precision 16-bit sigma-delta (Σ-Δ) ADC

and an on-chip oscillator. Consuming only 135 μA, the AD7171

is particularly suitable for portable or battery operated products

where very low power is a requirement. The AD7171 also has a

power-down mode in which the device consumes 5 μA, thus

increasing the battery life of the product.

For ease-of-use, all the features of the AD7171 are controlled by

dedicated pins. Each time a data read occurs, eight status bits

are appended to the 16-bit conversion. These status bits contain

a pattern sequence that can be used to confirm the validity of

the serial transfer.

The output data rate of the AD7171 is 125 Hz, whereas the

settling time is 24 ms. The AD7171 has one differential input

and a gain of 1. This is useful in applications where the user

needs to use an external amplifier to implement system-specific

filtering or gain requirements.

The AD7171 operates with a power supply from 2.7 V to 5.25 V.

It is available in a 10-lead LFCSP package.

The AD7170 is a 12-bit version of the AD7171. It has the same

feature set as the AD7171 and is pin-for-pin compatible.