Laptop motherboard theory

[Askic]

Hello guys,

I'm studying a schematics from a laptop and trying to get better understanding of various parts and their role in laptop motherboard. I'm not trying to fix any specific motherboard, but to gain more knowledge.

It is interesting for me a LID switch on a motherboard. I know it's a HALL sensor and when magnetic material gets close to it, it will switch. So basically it is a switch that opens or close depending how close metallic frame of screen is.


But which circuit (voltage) this switch close or open? I know this can be measure on the power button connector. This switch should cut power to the screen but also do something to send the computer to sleep.

Also, I wonder what accelerometer sensor do in a laptop moterboard. What is its role?

Thank you.

[caspian]

Re: Laptop motherboard theory

The circuit for LID switch usually resides on the Power-Button board which is not explained in the schematics.
An accelerometer in a laptop protects hard drive from damage. If the laptop is being suddenly dropped while being On, the accelerometer detects the sudden free fall and immediately turn off the hard drive.

[mcplslg123]

Re: Laptop motherboard theory

LID SW# is directly connected to EC. Its one of the basic input requirement of KBC. 3D3V_S5 is usually the input for LID switch(VDD) and its output is called as LID Close# or LID SW# which goes to kbc. If the LID switch is shorted, it may pull down 3D3V_S5 rail to ground making the unit dead.BLON_OUT signal originate from kbc only when it gets LID SW# confirmation. thats why sometimes we get dimm display for simple fault of LID.

[Askic]

Re: Laptop motherboard theory

Can anyone please show me how on actual motherboard connection shown in the attached picture looks like?

Thank you.

[stingerchamp]

Re: Laptop motherboard theory

https://www.badcaps.net/forum/showthread.php?t=91803Two pads connected

[Askic]

Re: Laptop motherboard theory

https://www.badcaps.net/forum/showthread.php?t=91803Two pads connected

Great, thank you stingerchamp!

[Askic]

Re: Laptop motherboard theory

Hello guys,

I also have one more question regarding the labels of the power states. Are the labels for power states the same regardless if laptop is Apple (Macbook) or any other PC laptop?
In other words is this valid to any laptop:
Computer is off – S5
Computer is hibernating – S4
Computer is sleeping – S3.
Computer is on and working, S0.


When I see this on the motherboard schematics:
+3V_S5
+3V
How to know when 3V S5 is present in comparison with +3V?

Thank you very much.

[piernov]

Re: Laptop motherboard theory

These are ACPI power states, they are described here: https://en.wikipedia.org/wiki/Advanc...e#Power_states

http://logi.wiki/index.php/ACPI_power_states (applied to Apple machines)

Exact naming depends on the platform. Schematics usually have a power state table telling you which power rails are turned on in which states. Usually, +xVALW is an S5 rail, +xVS is an S0 rail, +xVSUS sometimes is a DeepSx rail and sometimes it's an S3 rail.
The enable signal can also tells you when a power rail is supposed to come up.

[Askic]

Re: Laptop motherboard theory

Thank you piernov, this is the information I needed.