After much firmware development and some project delays, I have completed my testing on the LMP93601 with thermopile detectors in my specific product application. The device did not perform as I expected largely to the lack of gain in the primary input stage and the function of the digital gain. The digital gain function appears to just bit shift the ADC digital output so that high order ADC output bits are lost. So if you have a digital gain of 2 then you end up with a 15 bit ADC, digital gain of 32 gives you an 11 bit ADC. This did not perform well in my specific application because I need full 16 bit accuracy with a total gain in the 4000 range.
The other issue I had with the LMP93601 which I thought I could overcome was the fact that all inputs on one device have the same gain setting. This proved to be a problem due to different IR optical filters on each detector. The signal strengths were highly variable and I really needed independent gain on each detector channel. My application has 4 detectors and so I was using two LMP93601 devices and then assigning the detectors to devices by relative signal strength based on their IR optical filters.
At this point in time, I am abandoning the LMP93601 and searching for a new part. I'm looking for a part that has an analog programmable gain in the 4000 range with a 16 bit ADC minimum, differential input for thermopile sensor and can handle 4 channels. If anyone knows of a TI part that meets this specification then let me know.
