I have a customer that needs to digitize the output of a strain gauge. Their power source can vary from 1.6 to 3.6V and is capable of supplying no more than 200 uA. Ideally, they want to use a differential input A/D and want a SPI output. Sample rate is super low. Maybe one sample per minute. 8 bit accuracy is acceptable. The design is high volume 100-200K units and very cost sensitive The Maxim MAX1391 is being considered. As an alternative, I offered the AD7468 + AD8237. I have a few questions:
Attached is my initial idea
A couple new thoughts. Perhaps the AD8236 is a better fit for the Instrumentation amp. It is much lower power. Regarding the reference, I looked for something cheaper than the Maxim part and considered the following:
Both are very low power
Thanks Jonathan. I appreciate your input. The problem I have is that the solution must operate from a supply voltage of 1.8V to 3.6V. A solution that requires a 2.5V A/D will not fit this application.