STM8S001J3 ADC Maximum Input Impedance

[Wong]

What's the max Input Impedance of STM8S001J3? I couldn't find it on its datasheet.

I've found a couple of equations in page 11 of AN2752. If I keep slowing down the clock of the ADC, would I be able to increase the maximum input impedance as long as the equations in page 11 of AN2752 is satisfied? Or is there an additional value of maximum limit on the input impedance in addition of the equations there?