Is there anyway to get these links working again? They don't seem to be functional. Also, I'm assuming that the output of the voltage divider is unaffected by the capacitor.
So with a fully charged lithium ion batter (4.2V) you would expect to see a voltage of
4.2*(2.2/10) = .924V
Is the functionality of the circuit as follows? The capacitor is just acting to store up some charge to dump charge into the internal capacitor used by the ADC. It is essentially acting as a low impedance voltage source for the ADC sampling circuit?
The thought behind this setup is to have the voltage in the ADC input pin as close to 0.6V as possible. Then the current flowing in and out of the ADC is minimal and you can therefore have a small capacitor. If you would set the maximum ADC input voltage close to 1.2V then you would need a larger capacitor, perhaps 100 nF, which would also take longer to charge up between samples, and would limit the maximum sampling frequency a little more. But if you sample the battery with <1Hz then you could set R1=6Mohm and C=100nF which would lead to:
Maximum voltage on ADC input: 4.2V * 2.2M/(2.2M+6M) = 1.126V
Maximum ADC output value, 10-bit sampling: 1.126/1.21023= 961
Minimum voltage on ADC input: 2.7V * 2.2M/(2.2M+6M) = 0.724V
Minimum ADC output value, 10-bit sampling: 0.724/1.21023 = 617
Usable ADC resolution is: 961- 617 = 344
To compare, usable ADC resolution for the 10Mohm setup is 230
The thought behind this setup is to have the voltage in the ADC input pin as close to 0.6V as possible. Then the current flowing in and out of the ADC is minimal and you can therefore have a small capacitor. If you would set the maximum ADC input voltage close to 1.2V then you would need a larger capacitor, perhaps 100 nF, which would also take longer to charge up between samples, and would limit the maximum sampling frequency a little more. But if you sample the battery with <1Hz then you could set R1=6Mohm and C=100nF which would lead to:
Maximum voltage on ADC input: 4.2V * 2.2M/(2.2M+6M) = 1.126V
Maximum ADC output value, 10-bit sampling: 1.126/1.21023= 961
Minimum voltage on ADC input: 2.7V * 2.2M/(2.2M+6M) = 0.724V
Minimum ADC output value, 10-bit sampling: 0.724/1.21023 = 617
Usable ADC resolution is: 961- 617 = 344
To compare, usable ADC resolution for the 10Mohm setup is 230
