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
Power-down current: 12 μA maximum
Temperature range: −40°C to +125°C
20-lead LFCSP package
The AD7291 is a 12-bit, low power, 8-channel, successive
approximation analog-to-digital converter (ADC) with an
internal temperature sensor.
The device operates from a single 3.3 V power supply and
features an I2C-compatible interface. The device 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
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
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
8-Channel, I2C, 12-Bit SAR ADC
with Temperature Sensor
FUNCTIONAL BLOCK DIAGRAM
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.
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
Table 1. AD7291 and Related Products
Device Resolution Interface Features
8-channel, I2C, 12-bit SAR
ADC with temperature sensor
8-channel, 1 MSPS, 12-bit SAR
ADC with temperature sensor
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