I'm trying to implement oversampling on a dsPIC33EP64GS502. According to the datasheet and the 12-Bit High-Speed, Multiple SARs A/D Converter (ADC) reference manual I have to configure the following bits to set the oversampling ratio:
I'm struggling to understand why a 2x and a 4x oversampling both provides the same 13-bit result, the same for the other ratios. AFAIK a 4x oversampling will increase the resolution by 1 bit, a 2x ratio should increase the resolution in 0.5 bits. Is this an error on the datasheet or am I misunderstanding something?
Best Answer
The quantity of bits are those actually present in the result, not the resolution. As such they should be >= the resolution.
In other words, if the ADC has a resolution of 12 bits, the x2 oversampling gives you 0.5 bit more resolution but to report it you must use 13 bits.
So the result with 4x oversampling is 'better' in terms of resolution than the 2x oversampling but is presented to the same number of bits.