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Old 11-30-2021, 06:05 AM   #1
caspian
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Question How much output current is required on the Laptop rails?

Dear Technicians,

Lets consider the buck converter circuits that we see in Laptop mainboards including 3.3v, 5v, 1.05v, RAM power rail, CPU_Core rail, and GPU_Core rail. The schematics mention that such a buck converter circuit can provide the maximum output current such as 9A, 14A, or 16A.
What are the typical current and the maximum current that you observed in practice separately on these rails including 3.3v, 5v, 1.05v, RAM power rail, CPU_Core rail, and GPU_Core rail?
I mean, how much output current is required on these rails in practice?

Note: I do not mean the current provided by the AC adapter.

Thanks

Last edited by caspian; 11-30-2021 at 06:08 AM..
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Old 11-30-2021, 02:37 PM   #2
caspian
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Default Re: How much output current is required on the Laptop rails?

I attached the diagram of one of these buck converters for clarity. It says it can provide 12A typically and 18A maximally.
How much current is used in practice on various laptop power rails, typically and maximally?
Attached Images
File Type: jpg cpu1_Page_45.jpg (132.3 KB, 12 views)

Last edited by caspian; 11-30-2021 at 02:40 PM..
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Old 11-30-2021, 10:33 PM   #3
harrisnell
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Default Re: How much output current is required on the Laptop rails?

Image is clear but can someone summarize it to me.
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Old 12-01-2021, 12:42 AM   #4
caspian
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Default Re: How much output current is required on the Laptop rails?

Once I saw a laptop with a failed CPU_Core rail. Then, the repairman soldered a wire from the 1.05v rail to provide voltage for the CPU_Core rail. Surprisingly, it worked. He put the CPU under stress and it was working fine.
How can this be possible?
How can the 1.05v rail (that is kind of weak) provide the current required on the CPU_Core rail that is supposed to consume a lot of current?
How much current is required in practice on laptop rails?

Last edited by caspian; 12-01-2021 at 12:57 AM..
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