| ??? 05/19/08 15:14 Modified: 05/19/08 15:16 Read: times |
#154908 - Immanent flickering Responding to: ???'s previous message |
Richard said:
Wouldn't you conclude that any imperfection in the supply and in the input signal would be added to that? It isn't clear what's exactly going on inside a microcontroller when an analog input signal is converted in the built-in ADC. There are some certain instances when the ADC result is especially sensitive to noise, might it come form power supply or ground bounce or etc. Many micros have something like a "quiet modus", which allows you to switch off the most noisy circuitry within the micro, which is the ports driving sections, for instance, especially when driving heavy capacitive loads. I for myself use external ADCs, put the micro during the conversion into idle mode and wake him up by a /INT pulse coming from ADC. By this I can use a fast 12 bit ADC without any detoriation of performance. I have heard many times, that the internal ADC flickers, even when all sources of noise are wrestled down. So, 1...2LSB flickering noise might be the best you can get with a micro that has the ADC built-in. Kai |
