We received the assembled Rev4 boards which had some changes made to fix bugs and some additional features. Based on the tests performed so far, the changes work as expected.
The following features and performance have been tested:
Programmable output resistance: Checked the change in the output resistance from near 0 to about 10 Ohm. The output shows a linear drop with the output current with the slope equal to the output resistance. No stability issues seen as the resistance setting is added in the feedback loop
Output over voltage protection: If the output voltage goes above 7.2V, the protection circuits kicks in and turns Off the output relay. This ensures that the tool is protected from external high voltages. Short spikes of high voltage are suppressed by ESD protection
Output current limiting: The output current limiting feature is tested from limits ranging from 50mA to 2A and seems to work fine. The output remains constant till the limiting current and beyond that limit, the voltage drops off rapidly to clamp the output. This keeps the current at constant levels.
Short circuit protection: The output gets automatically cutoff when a short circuits is detected (current > 2.5A).
Reverse current protection: Checked the feature and does as expected.
Based on these tests, we have made some minor modifications to the final PCB and BOM.
We will order the final set of boards shortly and start the assembly for the final delivery in the coming weeks. We will get one prototype for EMI tests in the meanwhile.
If all goes as per plan, we are just in time to make the deliveries in the middle of Oct 2020.