Step Response Test

[dattatreyaroy]

Hello,

I have been using the passmark USB tester for step response tests and wanted to have the following information on the pulse currents used -

- Rate of rise and fall of the current pulse
- Duration of the current pulse

Please let me know.

Best regards,
Dattatreya Roy

[David (PassMark)]

~12ms for rise time and 1-8ms for fall time. The variability in the fall time depends on the initial current level when returning to the starting point after the step. If the target is above 0A (e.g., 100mA), the fall must be slower to avoid creating a pulse to zero instead of reaching the intended target current.

The graph is sampled at around 10kHz in PM125 hardware.
We are looking at moving to higher sampling frequencies for future hardware releases (e.g. 100kHz), which should give more detail on the graph.

Sample of load change from 0A to 3Amps

[dattatreyaroy]

Okay, thank you for the information. And for how long does the pulse stay at 3A value?

[Nik]

Hello,

The final load value of the step response (3A in this test case) is held throughout the entire 7.5ms that is plotted on the graph in Windows Application. After the test completes, the Application sets the load to 0 as this is safer to do and allows the fans to be turned off while you look at the graph. This means the exact length of the pulse may not be consistent and can depend on the PC, but the length of this pulse has no effect on the graph since the load is turned off after the test completes. If your testing requires that you see how the charger responds to the step response of the load turning off, then you can run the test again with the initial current set to 3A and final current to 0A to see that response as well.

[dattatreyaroy]

Okay, thank you for the information.