with Temperature Sensor

AD7291

Rev. 0

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FEATURES

12-bit SAR ADC

8 single-ended analog input channels

Analog input range: 0 V to 2.5 V

12-bit temperature-to-digital converter

Temperature sensor accuracy of ±1°C typical

Channel sequencer operation

Internal 2.5 V reference

fast speed modes

Out of range indicator/alert function

Autocycle mode

Power-down current: 12 μA maximum

Temperature range: −40°C to +125°C

20-lead LFCSP package

FUNCTIONAL BLOCK DIAGRAM

TEMP

SENSOR

12-BIT

SUCCESSIVE

APPROXIMATION

ADC

INPUT

MUX

T/H

GND

PD/RST

SCL

SDA

AS1

AS0

CONTROL LOGIC

SEQUENCER

BUF

REF

AD7291

ALERT

Figure 1.

GENERAL DESCRIPTION

The AD7291 is a 12-bit, low power, 8-channel, successive

approximation analog-to-digital converter (ADC) with an

internal temperature sensor.

The part operates from a single 3.3 V power supply and features

multiplexer and a track-and-hold amplifier than can handle

frequencies up to 30 MHz. The device has an on-chip 2.5 V

reference that can be disabled to allow the use of an external

reference.

The AD7291 provides a 2-wire serial interface compatible with

interface modes. The AD7291 normally remains in a partial

power-down state while not converting and powers up for

conversions. The conversion process can be controlled by a

operations or an autocycle mode selected through software

control.

The AD7291 includes a high accuracy band gap temperature

sensor, which is monitored and digitized by the 12-bit ADC to

give a resolution of 0.25°C.

The AD7291 offers a programmable sequencer, which enables

the selection of a preprogrammable sequence of channels for

conversion.

On-chip limit registers can be programmed with high and low

limits for the conversion results; an out-of-range indicator

output (ALERT) becomes active when the programmed high

or low limits are violated by the conversion result. This output

can be used as an interrupt.

PRODUCT HIGHLIGHTS

1.

Ideally suited to monitoring system variables in a variety

of systems including telecommunications, process control,

and industrial control.

2.

and fast modes.

3.

Automatic partial power-down while not converting to

maximize power efficiency.

4.

Channel sequencer operation.

5.

Integrated temperature sensor with 0.25°C resolution.

6.

Out of range indicator that can be software disabled or

enabled.

Table 1. AD7291 and Related Products

Device

Resolution

Interface

Features

AD7291

12-bit

ADC with temperature sensor

AD7298

12-bit

SPI

8-channel, 1 MSPS, 12-bit SAR

ADC with temperature sensor