The AD7291 of Analog Devices is a 12 bit, low-power, 8-channel SAR analog-to-digital converter (ADC) with a built-in temperature sensor. This ADC is powered by a 3.3 V power supply and has an I2c compatible interface. This part includes a 9-channel multiplexer and a track and hold amplifier, which can handle frequencies up to 30 MHz. The device has an on-chip 2.5 V reference, which can be disabled to allow the use of external references.
The AD7291 provides a 2-wire serial interface compatible with the I2C interface. I2C interface supports standard and fast I2C interface modes. ADC usually keeps part of the power off when not switching, but turns on the power when switching. The conversion process can be controlled through the command mode, where the conversion occurs in the I2C write operation or the autocycle mode selected through software control.
The AD7291 includes a high-precision band gap temperature sensor, which is monitored and digitized by 12 bit ADC to provide a resolution of 0.25 ° C. The device provides a programmable sequencer, which can select a pre programmable channel sequence for conversion. The chip upper limit register can be programmed to set the highest and lowest limit for the conversion result; The out of range indicator output (alarm) becomes active when the programmed high or low limit is violated by the conversion result. This output can be used as an interrupt.
