Figure 5. Sample-and-Conversion Process
Extending the Resolution of ADC12
To maintain accuracy across the entire current range, the 12-bit ADC resolution must be extended to approximately 15 bits. This is done by providing an additional gain of 16 on each current signal input to the ADC and using software to select which gain setting is the most suitable.
For each current signal, there are two sets of samples available to the ADC, one with low gain and one with high gain. The software chooses the largest nonsaturated signal available on a sample-by-sample basis. This signal is then gain adjusted and phase compensated according to the input it is taken from. Figure 6 shows this process: