Power supply spikes exceeding the resistors power rating. Enable pin control of the U1

[Sergio5714]

**Issue:**The power spikes on the supply line VSYS_IN may exceed the power rating of the current measurement resistors R1, R5, R6, R8, R9, R10, R11, R13.
Potential solution: Replacing the aforementioned resistors (1 Ohm) with 0.1 Ohm alternatives with the same footprint.

Issue: EN_HV (pin 5 of the U1 DC-DC) connector is probably floating when the MSP430 is not programmed. According to the datasheet of TLV62569, it should not be left floating.
Potential solution: Placing a weak pull-down resistor to fix the disabled state by default.

[Ethan010722]

Subject: Issue with EN_HV Pin and Missing 15V Output After Programming MSP430

Hi Sergio,

Thank you for your work on this project. I’ve encountered an issue with the HV board: after programming the MSP430, the 15V high voltage is not generated. I measured the EN_HV pin (Pin 5 of U1, TLV62569), and it shows 0V.

I’ve already tried connecting a 10k pull-up resistor to the EN_HV pin, but it didn’t resolve the issue. Could you advise on what might be causing this problem and how I could fix it?

Looking forward to your guidance!

Best regards,
Ethan

[Sergio5714]

Hi @Ethan010722, thank you for your question.

In the WULPUS firmware of the MSP430, we are actively power gating the HV rail. That means it is active only during the acquisition. Otherwise, the EN pin of the LT1945 DC-DC converter is disabled and the output remains around zero. Please do the measurements with the oscilloscope during the acquisition.

However, the U1 of the acquisition PCB is supplying the entire HV PCB and it must be enabled.
In the firmware, we call the following function

wulpus/fw/msp430/wulpus_msp430_firmware/wulpus/wulpus_sys.c

Line 211 in cf9fd17

void enableHvPcbSupply(void)

in the main.c we enable the U1 after receiving the configuration package from the PC (earlier than this moment it stays disabled):

wulpus/fw/msp430/wulpus_msp430_firmware/main.c

Line 83 in cf9fd17

enableHvPcbSupply();

Could you please run the MSP430 in the debug mode line by line with a breakpoint on the above line, and check the status of the EN_HV pin (U1) after sending the configuration package (i.e. after pressing "Start acquisition" in the GUI)?

[Sergio5714]

We fixed this issue and merged the changes into the dev branch. The changes will be a part of the release 1.2.0.