ADS1118: RE: SCH review request.

Hello Hrishikesh,

Schematic review:

One item that is missing is antialiasing filters on the inputs of the ADC. Section 10.1.3 Analog Input Filtering of the datasheet describes the purpose of the filters, take a look and let me know if you have any questions about them. I'll note in some special cases a very low bandwidth amplifier might be able to act as a filter but this is not the case for the INA185. You can find an example in the applications section of the datasheet or in the schematic at the end of the ADS1118EVM user guide: https://www.ti.com/lit/ug/sbau357/sbau357.pdf . This is the most critical item missing from the schematic.

Error:

For the error, let me get back to you on that request within a couple of days. Could you provide the intended sample rates? It helps with the noise calculation.

However, I can already tell you're not utilizing all of the full-scale range. My math seems to suggest your maximum voltage is 3V and the closest FSR would be +/-4.096V, so you're only using half the FSR with and you're only utilizing ~73% of that positive range. Setting AINx to 1.5V (or half your maximum VIN) to turn this single ended measurement into a puesdo-differential measurement could help with utilizing more of that range, though I'm not sure if that's compatible with all your mux settings.

General tips:

I would highly recommend using the device in single capture mode as it actually makes the software flow easier when switching between multiple inputs using a MUX. You would think that continuous is better for delays but the single sampling nature of the ADS1018 allows you set a configuration and start to convert in one transaction when you have to wait for a previous conversion to complete for continuous capture.

Best,

-Cole