Electronics > Repair
CH341A Serial Memory Programmer Power Supply Fix
magic:
I suppose the 3.3V reg is used to power USB so the USB interface operates at reduced voltage without this connection because of losses in the internal regulator. Not a big deal if it works, but I would fix it.
Mcast:
--- Quote ---I suppose the 3.3V reg is used to power USB so the USB interface operates at reduced voltage without this connection because of losses in the internal regulator. Not a big deal if it works, but I would fix it.
--- End quote ---
I tried to do what you said, I disconnected pin 28 and left only pin 9 powered, the device didn't turn on. I believe that there are other components within the integrated circuit that need power from pin 28.
magic:
No, that's not what I meant. It looks like everything on this chip runs from VCC except for USB communications which require 3.3V.
When VCC=5V the chip generates V3 internally. When VCC=3.3V the internal regulator will output less than 3.3V on V3 so USB may work if you are lucky or it may sometimes fail to work. That's why you short V3 toVCC.
fearconte:
Hi,
I have a CH341A Pro black "edition" and I tried to read some chips using clamp (chips are on board soldered), first the Detect doesn't work - ok china - i have selected the correct chip from list and read the chip.
on second read some data shifted and I was like this is not ok the chip is a Winbond W25X10
I have tried on different chip a PMC PM25LV512A which was read ok multiple times - erase - write - all good, strange but works with PMC not with Winbond which I need.
So I have searched the web and saw this post about the voltage, checked mine - 5V everywhere and I have started the mod using the OP
Lifted the pin 28 connect to C3 then to 1117 tested - success 3.3V - tried to Detect the chip still not working, tried to read, erase, program all error
Then I have tried next mod pin 28 to 1117 and pin 9 to 1117 - 3.3V but the same errors
Any ideas?
Thank you!
Mcast:
--- Quote ---No, that's not what I meant. It looks like everything on this chip runs from VCC except for USB communications which require 3.3V.
When VCC=5V the chip generates V3 internally. When VCC=3.3V the internal regulator will output less than 3.3V on V3 so USB may work if you are lucky or it may sometimes fail to work. That's why you short V3 toVCC.
--- End quote ---
Now I get it. I measured it and the difference between Vcc and V3 was about 130 millivolt, there is a loss of voltage too.
It's like 78xx, the regulator starts to become unstable (with noise, variation and the whole thing) when the input voltage stays the same with the output voltage.
I made the change, thank you all!
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