LDO on the board getting hot and board fail to respond

[finevlad]

Hi,

Noticed after a bit time issues connecting the analyser board.
Leaving it off for some time to cool the LDOs would result in normal connection to the board again.

Any recommendations?
I guess changing the cheapest parts to the more expensive ones could potentially sort the issue?

The better approach would be to use the switch converters?

[ian]

I'm sorry about the problem thank you for the report.

My guess is a short somewhere on the PCB. Do you know which ldo it is?

Im sure you could send it back for repair or replacement.

[finevlad]

My first impression is that the PCB is clean and none of the other elements provide any extra heat. If you say it is the only board with the issue I would replace the ldos myself as replacing the whole PCB would take some time and I need it working right now. Again it can be faulty ldo itself (this can happen to any IC I understand). Will do more investigations tonight.

[finevlad]

Checked last night. Need around 1 hour to have the condition repeat. The most hot is 1.2V LDO then 2.5V and the least is 3.3V. The output voltage of the 2.5 is triangular shape of the noise and the highest amplitude. nearly no pulsation on 3.3 one and some on the 1.2. At the disconnect happening the pulsation on the 2.5 and 1.2 rise by 40mV. Not very good in absolute value as the scope was using is not as accurate. Speeding cooling of LDOs (1.2 & 2.5) with cooling liquid would bring the pcb to acting state. So have two suspects now. Will try changing one at a time. Can you specify which exactly ones are used in the latest PCBs?

[ian]

MIC5205 (i think) is the standard part number, but we use whatever the most modern LDO in the package is. Last time I bought them from mouser it was a fairchild semi part (FAN-something if I recall).

[finevlad]

Replaced the 2.5V LDO and issue is gone now. Later friend of mine bought the same board and we tried the same scenarios and it was working with no problem. So consider the LDO on my board was faulty.

[ian]

Thanks for the update, I'm sorry about the broken board. Glad you got it going.