ADS1015 input capacitance

Patrick,


If you look at Figure 12 in the ADS1015 datasheet, you'll see that the input is a switched capacitor network that samples the input. The size of the sampling capacitors is dependent on gain and you can calculate the capacitance based on the values in Table 2 for the differential input impedance.

As an example, the full scale range at ±0.256V has an input impedance of 710kΩ. Since the fclk runs at 250kHz, and the input impedance is equal to 1/(C*fclk). The sampling capacitance is about 5.6pF.

There's probably some extra capacitance for bond pad in the device and some additional parasitic capacitance on the board and in the device, but I'd say that 10pF is a good estimate for that gain. It probably has a minimum of about 6pF in higher gains.


Joseph Wu