Unexpected SYS Drop on MP2632 EVM When USB Source Is Plugged In

Battery Management
1

Hi,

We are using the MP2632 EVM, powered by a battery, with the micro USB port initially left floating. The SYS output is connected to an electronic load set to 200 mA. I observed that when a PC or USB adapter is connected to the micro USB port, the 5 V boost output on SYS drops to 0–1.5 V. The voltage only recovers to 5 V after the electronic load is turned off.

Interestingly, when using a bench power supply instead of the USB port, the system operates normally.

Is there a recommended way to resolve this issue?

2

Hey Willy,

Apologies for the delay here.

I want to ask about what you initially said the MP2632 is initially powered by a battery, but the issue here arises when plugging in a USB which leads to the drop at the SYS pin down from 5V to 0V - 0.15V? Does this stay this way?

3

Another question, are there any updates to your issue before we dive further in debugging?

4

Just as an initial hunch, I feel there may be an issue with the power path management transition where in the case you plug in the USB, the power path of the MP2632, the power path controller likely attempts to switch the power source priority.

There could also be a USB inrush issue whereas a bench supply provides a clean signal. I would be interested in seeing the difference between these waveforms which would likely be the best place to start debugging here.

5

Hi Krishan,

Thanks for your reply. I believe the root cause is the limited drive capability of the power source. As shown in the image below, the drop in VBUS caused the 5 V boost at the SYS pin to fail when connecting to the PC. To address this issue, I may need to add an additional PD controller to enable higher current output from the PC or USB adapter. However, this would compromise my original goal of minimizing PCB size with this solution.

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image1035×788 89 KB

6

Hello again Willy,

I would encourage you to take a look at some of the PD controllers that MPS has to offer in that case. What are you using right now? What are the size constraints that you are facing?

7

Hi Krishan, thank you for your support. After further consideration, we’ve decided to revert to the PD solution used in the original module reference design in order to reduce firmware migration effort. As a result, we won’t be adopting your solution for this project this time.