AD7291_11 Datasheet, PDF (1/28 Pages) Analog Devices – 8-Channel, I2C, 12-Bit SAR ADC with Temperature Sensor

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
Specified for VDD of 2.8 V to 3.6 V
Logic voltage VDRIVE = 1.65 V to 3.6 V
Internal 2.5 V reference
I²C-compatible serial interface supports standard and
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
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
an I²C-compatible interface. The part contains a 9-channel
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
I²C interfaces. The I²C interface supports standard and fast I²C
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
command mode where conversions occur across I²C write
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.
8-Channel, I²C, 12-Bit SAR ADC
with Temperature Sensor
AD7291
FUNCTIONAL BLOCK DIAGRAM
V_DD
GND
V_REF
REF
BUF
V_IN0
12-BIT
T/H
SUCCESSIVE
APPROXIMATION
ADC
V_IN7
INPUT
MUX
AD7291
TEMP
SENSOR
SEQUENCER
CONTROL LOGIC
I²C INTERFACE
PD/RST
ALERT
Figure 1.
SCL
SDA
AS1
AS0
V_DRIVE
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. I²C-compatible serial interface, which supports standard
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
I²C
8-channel, I²C, 12-bit SAR
ADC with temperature sensor
AD7298 12-bit
SPI
8-channel, 1 MSPS, 12-bit SAR
ADC with temperature sensor
Rev. 0
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