Electronic – How to calculate rise times for a push pull GPIO with load with hand calculations

digital-logicrise time


simulate this circuit – Schematic created using CircuitLab

This is a simplified example of a push pull GPIO found in most microprocessors, with a load attached.

Using the capacitance and current values from the datasheet that is usually given in a microprocessor datasheet, how can the rise time be calculated?

Best Answer

For this, and if you have access to it, you should better use IBIS models for the I/O cell.

The IBIS model not only provide for rise time and fall time modelling but also includes ESD diodes modelling which will make your simulations much more accurate (see Fig 9. for diagram).