Photodiode to an ADC
The max input current is most likely the mux leakage current. 



By inspecting the equivalent input circuit, it is high impedance as there are two capacitors that capcititivly couple the input signals to the ADC core.  These currents are likely to be negligible and the current that the LT6202 needs to source is 1uA which is well within its capability. 



ADCs generally keep the input impedance high (input current low) because any load from an ADC will contribute to error when sampling\switching.