Similar microcontroller to F2802x, but with 5V ADC?

Hi Laura,

If the voltages you want to sample are higher than 3.3V, use a resistive voltage divider or op-amp circuit with fractional gain to get the input signal into range.

Hi Devin,

Thank you so much for your response. Those are both great suggestions, however, the problem is with resolution of the signal that I want. My current set-up is a pressure sensor with a 39 mV range. The signal from the pressure sensor (from a blood pressure cuff) goes to an in-amp. Afterwards, the signal goes to the C2000 ADC pin (after going through a low-pass filter). I must filter the signal in the C code to measure small oscillations in the signal (see figure in website: www.sensorzine.com/.../digital-blood-pressure-meter-freescales-application-note-page3-724300.jpg). If the oscillations have not been amplified enough (>10 mV) then I run into noise issues.

So, in short, the only thing that I can think of is a larger voltage range. I also would like the microcontroller to have the same memory as the C2000 F28027 (12 KB of RAM). Suggestions?

If you scope the input to the ADC, does it look like figure 3 or figure 4? (Since they are using an 8-bit ADC in the application note, it seems like the raw ADC input would have to be similar to figure 4).

You can also look at is the noise performance of the op-amp or instrumentation amp that you are using. This noise is usually specified as input referred, so gaining-up the signal more won't help (the same is also true if the noise you are seeing is introduced to the signal before the input of the amp).