Troubleshooting ACT8846 power management IC. Micro gets stuck at startup.  - Page 1
Forum section: electronics / repair

author: Yamin
author_rank: Frequent Contributor
timestamp: August 06, 2020, 09:48:42 pm
content: Hi guys,I am trying to troubleshoot a guitar pedal board which has got a Rock2 SoM module (its based on the Rockchip RK328). The unit shuts down on start up. It has got a ‘soft latching power switch’. I have two identical faulty boards same symptoms. I’m working on one board removing and re-soldering components trying to troubleshoot. I just need one working board.There is a Mosfet used to turn on the power to the whole board. I have bypassed this and I am powering the board directly from a 12V supply. Pressing the ON button initialises the start up process just like before but instead of turning off the voltages remains. I have checked all the DC/DC converter ICs outputs and LDOs. Everything seems to be in working order.Potential issue:I think I have zeroed in on the problem. I could be way off, but definitely something interesting. The ACT8846 chip is used as the power management IC for the module. Here’s what I noticedThere is 5V at the INL1, INL2, INL3 pins and I measured 0.3V at OUT9 and 0V at OUT8. Why I measured those first were because ‘VCCIO_PMU’ is used for the reset IC - U2207.I was really hoping for something simple like shorted out coupling cap but it doesn’t seem to be so.I have tried manually resetting the IC described on the page 31 on the data-sheet, but this was before I had the main supply latched.I was hoping that someone could give me further advice on what to troubleshoot and what to look for? I am aware that the microprocessor could be bricked as well, any idea how to ‘un-brick’ it?Thanks in advance for the help.Rock2 SoMhttps://wiki.radxa.com/Rock2/somRock2 SoM schematichttps://dl.radxa.com/rock2/docs/hw/radxa_rock2_som_140927.pdf

author: Yamin
author_rank: Frequent Contributor
timestamp: August 06, 2020, 10:20:57 pm
content: I have been trying to upload a photo of the cropped schematic but doesn't seem to go through. The ACT8846 IC is on page 9 of the schematic - link attached.

author: fzabkar
author_rank: Super Contributor
timestamp: August 06, 2020, 11:30:01 pm
content: Have you checked pins 31, 32, 16?https://www.mouser.com/ds/2/631/ACT8846_Datasheet-346019.pdf

author: Yamin
author_rank: Frequent Contributor
timestamp: August 07, 2020, 03:52:19 pm
content: Thanks @fzbkar,I have taken the mentioned measurements.From the 'latched' board:Pin 16 PWREN = 2.01 (varying)Pin 31 nPBIN = 4.75VPin 32 PWRHLD = 1.4VFrom the second board which I haven't messed with:This is the voltage measured when the power switch is pressed, all the measured values goes to 0V when it turns off when it fails to boot up.Pin 16 PWREN = 4.6VPin 31 nPBIN = 4.7VPin 32 PWRHLD = 4.6VSomething else I noticed wasI measured the voltage at Pin 33 nRTSO (this is the pin the rest IC is connected) when I first powered on the board without pushing the ON button I thought I saw 3.3V there. When I pressed the ON button the voltage there was around 1.9V . I didn't see 3.3V again. I unplugged the board from the mains left it for sometime powered it back on and still no 3.3V at the pin :S . But 1.8V to 1.9V always seem to remain at the pin regardless of pushing the ON button or not.Thanks so much for the help

author: fzabkar
author_rank: Super Contributor
timestamp: August 07, 2020, 07:40:34 pm
content: ISTM that you need to locate the source of the PWR_EN signal and troubleshoot that.