The prototype version of PocketPD utilizes a sense resistor of 10mOhm to measure the current reading of the load. Here is the configuration for V.Prototype:

The power goes directly from USB-C VBUS, and passes through the sense resistor, thru the PMOS output switch to the banana jack terminals.

Issue: VBUS reading is higher than VOUT, more than expected. There must be more voltage drop somewhere.

It was a bit surprising that Ron is consistent across multiple input voltages as Vgs and Ron are dependent on each other. Further investigation is needed

Conclusion: The resistance of PMOS (68mOhm) is higher than expected (18mOhm) which causes the discrepancy between the OLED measured and the Banana jack output. 

Solution:

• Use the known resistance drop across the PMOS. Calculate the expected voltage drop with current. Display the adjusted VBUS value
• Move the current sensing to just before the banana jack. This will take care if there need to be component changes on PMOS due to part shortage or part upgrade. 

But !... The current reading is now calibrated. We are getting the correct amperage report through the Rsense resistor!