ADC, pref and dynamic range
Still relatively new to ADC'ing, so just want to float a couple of concepts to mkae sure I have them squared away.
Consider a analogue signal 1.024V max peak to peak - with an ADC +ref of VCC @5v....you're not gonna get much range, so what are the options....
1 amplify the actual signal before it gets to the ADC PIN. (uses more components)
2 use a PIC on a lower VCC (say an LF variant at 1.8V - which may necessitate an extra regulator)
3. use a pic that allows you to set the ADC +ve ref.
It's this last option that I hold an interest - a 16lf1824 has an internal 1.024V fixed voltage reference....so using that for the adc pref for the earlier example, would yield the maximum ADC dynamic range.
But what if the signal is only 500mV? Is is a deemed reasonable solution to keep going down if reference level ...ie put a fixed vref of 0.5v on the PIC's ext vref pin (vs simpy amplifying the signal)....how low can we practically take the ADC 'pref' to getter better dynamic range? (& what are the gotchas!)
cheers,
Hank
Bookmarks