I accidentally shorted few Raspberry pi 3b+ by powering them with 12v adapter instead of 5. Most of them had shorted PMIC mxl7704 r3. Short was gone after removing that IC. I imported some of these chips from China. But after replacing them the pi isn’t showing any power draw, I used chatgpt and it said it’s pre programmed so I assumed that these chips were fake and ordered some from a different seller and these have same issue as well.
Today I saw this where it mentions that it needs to programmed via I2C to work, btw here the chip is r4 version which is used in pi4 . I’m very confused rn.
@rsaeon might know something.
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You can’t program the PMIC, this is under NDA and is not publicly available by the max linear.
Max linear gives the OTP and programming sequence to only its high value customers like raspberry pi.
There is no way to program the IC. Even with i2c you will not know what register to program with what value and in what sequence.
And the OTP is only one time programmable.
If wrong value is programmed the chip is dead.
Only fix is to get the IC from another RPI B+.
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For the 3B, several users have reported that dropping in a Chinese replacement fixed it. But their PMIC didn’t die from overvoltage, it was from a short.
On a dead 3B with the original pmic still soldered on, check the Vcore after power on. Or check Vcore resistance back to wherever you fed 12V and/or ground. If the Vcore is over 1.3V or there’s low resistance, then the SoC is dead.
For the 3B where you did replace the PMIC, did you check the output voltage?
PMIC gets extremely hot when I power it on so I dint risk measuring voltage. Vcore resistance was normal on most of them. It worked when I replaced the PMIC from an working raspberry pi 3b
This is RPI4, the PMIC it uses allows this.
But the PMIC of 3B+ doesn’t.
I don’t think you can use the PMIC of rpi4 on 3b+.
Check the pinouts to confirm.
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RPI3B+ is the weird one.
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