Rpi CM4 Power Up Sequence ??

[Swaroop 21]

I have a Rpi CM4 but its onboard regulator was nuked so it was shorting every voltage rail to ground. I have currently desoldered the IC so now the short isn't there anymore but is there any way to inject the voltage using external regulators but i don't know what voltages and the sequence of getting them up maybe is there a schematic or points marked with voltages ? I see 4 inductors around the PMIC so I guess 4 different rails ? I read somewhere that someone managed to get a model 4B+ running again with a replacement of the PMIC without needing to program the power up sequence in the new soldered PMIC.

[wraper]

If it's MXL7704-P4 (they are factory programmed, P4 is a custom version for rpi4), you can get it on aliexpress. There is reduced schematic is available for pi4 model b https://datasheets.raspberrypi.com/rpi4/raspberry-pi-4-reduced-schematics.pdf
If it's a newer revision with DA9090, it's not available anywhere, can only be salvaged from another board.
Simply applying voltages won't work, you'll probably see a bootloader screen, but normal OS images won't boot unless proper PMIC can be communicated via I2C, and that's the reason why DA9090 and MXL7704 are not interchangeable, despite being very similar.

[wasedadoc]

https://forums.raspberrypi.com/viewtopic.php?p=2235013#p2235013

[wraper]

https://forums.raspberrypi.com/viewtopic.php?p=2235013#p2235013

Last post you linked to sounds like BS. Part number for DA9090 is DA9090 and Renesas programs it per customer's requirement. EDIT: I see it's posted by raspberry pi engineer/moderator. Still SC0591X is strange, is it some internal part number from raspberry pi foundation? Also there is a pin compatible DA9080 with publicly available datasheet (unlike DA9090 with no info) and which you actually can order in small quantity with supposed lead time of 6 months. I actually ordered 5 of them from Digikey in February just in case they might work on Pi 4, then Digikey contacted me in May asking to confirm I want them unprogrammed (default config shown in datasheet seems close enough, only RAM Vcore would be 0.1v too high by default, hopefully they are actually functional while unprogrammed. They replied that will forward it to Renesas. Still waiting if they'll materialize.
As emulation on MCU, completely plausible if you want to bother bodging it.

[Swaroop 21]

The problem with a replacement IC is stores like AliExpress and Banggood the shippments from this are banned in India the websites still works but when I go to checkout it just simply says unable to ship to your country. Even if there's any way to import them by third party exporter or something probably it would cost more than the CM4 itself. Finding the IC locally here will be next to impossible. I also have an Older Pi 4B model which has the same issue of blown PMIC.
Seems like the Pi4's and the new model 3B+ are more susceptible to damage because of shorting the power rails. Another older model of 3B just died when I powered it, everything was working fine one day I powered it up and the IC near the USB ports got super hot and now the Pi doesnt boot I dont remember doing any thing wrong with the Pi neither plugging in anything into the USB itself.

[wraper]

They're available on ebay too. If by chance you cannot buy there either, I could salvage some MXL7704-P4 from bad bards with a good PMIC.

Another older model of 3B just died when I powered it, everything was working fine one day I powered it up and the IC near the USB ports got super hot and now the Pi doesnt boot I dont remember doing any thing wrong with the Pi neither plugging in anything into the USB itself.

Those usually have a bad TVS if overvolted or/and RT8088A buck converter dies. PAM2306 dual buck is way more robust but sometimes dies too. USB hub IC sometimes dies, but it will draw a lot of current and heat if one voltage is missing, don't recall if it was 3.3V or 1.8V.