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General Power and switching system on Laptop Motherboard

General Power and switching system on Laptop Motherboard

1.VALW / Power Always or MAIN DC POWER SUPPLY CIRCUIT LINE

Power used is DC ( Direct current ) DC voltage  in use 19V 3.2A generally but there is also  15V - 20V  adapter RANGE voltage used depend on LAPTOP brands.

It better to use motherboard manufacture by using Motherboard code ,we would know how much adapter voltage usage. Clavo motherboard manufacture usually use for 18.5V~3.2a Quanta 19V~3.4a   Toshiba(15V-19V) , IBM(16V-19V) Compal-Inventec-Winstron- etc. ) .

VALW also supplying adapter current sensor detector detected by charger IC (see datasheet to know how system charging/discharging work) ,When the charger ic sensor detects  current adapter present ACIN~ACDET function pin on schema )and confirmed to SIO to manage charging system .

Acin / ACEDET is important as the voltage sensor for ic voltage charger to pass (adp) Adapter fets current, passed several resistor voltage 19V voltage scaled according to demand charger ic (V.i.R)..

The are standard voltage for sensor each Charger ic .Open datasheet ic charger  concerned for more detail .

VALW /Always Voltage The main VALW supply comes from adaptor, Started from DC jack flow to MAIN VALW Circuit. this is a MAIN POWER INSTALATION  ON CIRCUIT ,some of using FUSE (F) to safety reason some not. This main power supply circuit using 1 or more P Channel mosfet transistor to maintain stabilized power and distribute power for Charger IC and DC/DC main power supply IC as VCC Power supply. This is important power need to activate that component .Main power also contribute N channel source adapter voltage need  processed by the DC / DC main power supply  IC (see the datasheet to know how this ic work) produced 3V and 5V_ALW and supply whole 5V and 3V device. if one of this Power missing motherboard will not be able to live or referred to the dead .

Before discussing the Power 5V and 3V_ALW should we understand the pathways 19V_ALW . Starting from Jack Power Adaptor sure incoming voltage by a voltage adapter . example is work at 19V~3.2a

Make sure the voltage is present 19V_ALW or (according adapter voltage) for ic charger / Battery ic VCC and for adapter current sensor detector (greater than 2.4V). missing this supply 19V stop by CSIP than 19V  blocked by Analog ground coming from charging IC .some other board  blocking 19V by closing/opening gate P channel mosfet . Than 19V stop and won't supply to +BAT line and deactivated motherboard 3V and 5V system.

 DC / DC main power supply ic and upper /hi N channel (Source )need 19V  adapter voltage as VCC power to activated component.

and how to work the upper and lower N channel 5V and 3V voltage distribution

2.VS the Power Switch

VS is voltage that appears after switch on than switch button send a signal through EC_ON# (different board manufacture may have different pin name) to SIO or lately know by EMBEDDED CONTROLLER(EC) .than EC started to regulated signal by given signal gate to powered any device on VS state .

VALW main power supply standby to get N channel Sources when the signal   ( open / close Gate ) transistor to pass voltage through Mosfet ( Drain ) as much as gate requirement than become Source for

VS voltage .

The first one that must be understood is how the system works to enable/disable Power on VS

Laptop requirements in order to switch on first are the availability of 3V and 5VALW. Careful when finding 5VALW missing , switched on first cause of several motherboard, 5VALW appear after switch on .Than 3V_ALW or 3VPCU provide power supply to the EC , BIOS IC , South Bridge ( SB ) , clock generator and oscillator on ALW voltage .
VSB or switch voltage button (3.3V) will appear after Bios and EC powered. some of laptop motherboard will found 17V switch voltage on one of pin switch button but after switch -on voltage is changed to be 3.3 V. This is normal. Press power button ( short to ground ) then 3.3VSB will turn into 0V and back to 3.3V.and if standby VSB 17V press power button VSB become 0V and back to 3.3V. than power button is a good sign .

Steps further is the signal being sent to the EC ( Embedded controller NPCE 885LAODX ) signal names is NBSWON # most other brands of EC signal name may SW_ON, EC_ON or whatever name of the signal as long as signal coming from SW1 sent to EC , this voltage must respond in the same manner of testing power button , BIOS IC and firmware connected to SPI interface to the EC .Signal confirmation to ensure EC BIOS working properly is RSMRST # for3.3V.RSMRST# signal sometimes appear after switch on and other motherboard without switch on 3.3 V already present .

Modern Motherboard has 2 or 3 IC BIOS. Identified EC BIOS which is usually one-page schema with EC names EC BIOS.

Other important signal from EC is DNBSWON # ,this is PWR_BTN signal to switch on South bridge sent by the EC after receiving NBSWON # signal from power button. DNBSWON # 3.3V must be present otherwise it would not switch on , after this signal appears then the SB will sent SUSCLK # signal back to the EC and turn on VS as trigger for all switching gate driver as VR_ON , Suson , MAINON , S5_ON or SLP_S3 , SLP_S4 and SLP_S5 . and for all the Vs voltage to the Device .

VS POWER SUPPLY  for  BOOTSTRAP DEVICE :

There are three BOOTSTRAP device :

Processor -Sodim -NB/SB/GPU chip ,each device has a different names of power

PROCESSOR  power name by VCCORE-CPUCORE.

SODIM  power name by VCCRAM.

CHIP power  name by VCCP .

With out this power the device won't display or not able to load boot up process .

VS for Strap Boot device :

1.Procesor ( VCCORE ) Standard voltage 0.9 VS - 1.5VS

see VCCORE ic power required and how it works

How to test the voltage spike VCCORE ( processor power surge )

2.SODIM/RAM  ( VCCRAM ) 

Standard Voltage rail  for DDRII is 1.8VS and 0.9VTT

and for DDRIII for 1.5VS and 0.75 VTT 

3.CHIP POWER ( VCCP ) 

see each chip datasheet to get Voltage rail get know their power sources come from including stepping signal enable through S5~S0 sleep state.

VS to Device

( Lcd / led , hdd , optical , usb , wifi , bloutooth , keyboard ,

sound , camera etc. ) For details on each Rail Voltage VS can be seen in the

schema INDEX FOR EACH DEVICE.

 3.Signal 

( the wave trigger / sensor /2 way confirmation signal / data interface)

Signal function is open / close gate charge of organizing stages enable / disable each component or PCI ( Peripheral communication interface ) . system signal regulated by Microcontroller where the manufacturer

has made the format settings the form of firmware that is planted into the bios IC to managed embedded

controlling input output system  for each ic interface. .

Differences circuit and component arrangement on the motherboard of course require

different settings Microcontroller , so  each different motherboard brand and series firmware will necessarily require different settings

MOSFET TYPES FOR LAPTOP

Mosfet Type on Laptop Motherboard

There are  4 type of mosfet's SO8 on laptop motherboard

1. P channel mosfet
2.N chanel mosfet
3.dual P channel mosfet
4.Dual N chanel mosfet
each type could substitute as long as same type even with different marking code.
Easy way to identified look at the end number of marking code .
example  :
AO 4433 look at end of marking code number is odd numbers ( 3 )

this is P channel
example   : AO 4407 (7) is odd number ,this is P channel too,
they could be substitute each other even different manufacture and code.
Others P chanel examples :
AF 4825-AM 3423-FDS 6679-SI 4835 ETC

Other example : AOD 4466

look at last number of marking code it is even (6) numbers it's mean this is N channel mosfet and they could replace by other N channel even different
manufacture and code .

 Others N channel mosfet examples: AO 4800

AO 4474-AP 4232-FDMC8844-SI 4812 ETC

those mosfet identified only for SO8 mosfet.

We can see P channel mosfet function on this "GENERAL LAPTOP MAIN POWER 

  There are only 3 pcs P channel there ,2 pcs ADP(adapter) fet's and 1pcs Bat (battery)fet .some
motherboard also may have 1 adp Fet,some replace with diodes to supply every adapter supply need.
I call it "VALW MAIN LINE" .from this line  Battery ic and dc/dc power supply ic get VCC to powered each ic and this main VALW line also distributed adapterVoltage to every N channel Source ,before they got enable trigger to produced 3 and 5V_ALW......

P-channel mosfet works  drain is a input for nagative supply and source is a output for nagative supply ,and it's gate on with nagative volt .same way if you want to drive positive supply from p-channel mosfet then souce is input and drain is output for positive supply .

This is How 2 pcs P chanel replace by 1 Dual P chanel Mosfet

Look at this lay out function N channel mosfet  as integrated circuit with DC/DC main power supply to produce 3V and 5V_ALW

and what happen if P or N channel leak and what if suppose N channel replace with and P channel and what damage it could be

How DC/DC main power supply open/close gate N channel to produce 3V and 5V_ALW and important signal enable/disable function to activate the DC/DC main supply ic (ISL 6237-RT 8206-TPS 51247)

How do (RT8223-TPS 51125-TPS 51123)work and signal

If you confused ,you should read this before  

Introduction of System Power Laptop Motherboard

and to avoid accident before repairing you shoul read 

THINGS THAT SHOULD NOT BE TAKEN IN MOTHERBOARD REPAIR

We will also found (SO3) P channel ,(SO8)  mean mosfet have 8pin and (SO)3 mean they
have 3 pin.And this (SO3) also have P or N channel type .so be ware if you
want to make replacement .just make sure replace it whit same type .

Other way to Identified for (SO6) and (SO3) Mosfet transistors are by finding the marking code on ic than
browse the data sheet , if they not found get mosfet location code on board than
find on schema by typing marking code to adobe reader search column to look the correct marking code than browsing the datasheet again to get know mosfet type and get substitution...
this is one of sample N channel (SO3) code  : 2N7002 -P0603BDG

samples (SO3) P channel mosfet :
FDD6685 - SI12301 -TP0610K.
sample datasheet link for N channel (SO3) 2N7002 :http://www.fairchildsemi.com/ds/2N/2N7000.pdf

2 mosfet in one package ,it is a simply vrm switching mosfet circuit in single mosfet package ,drain connected with diode cathode and source is connected with anode that how to identified  a N-Channel mosfet.

N chanel caracter common base

n-channel mosfet voltage flow is drain to source for positive supply - when you apply + positive volt in gate then this mosfet drive voltage drain to souce ( gate works same as transister base) if you want to drive nagative volt from n-channel mosfet then nagative volt drive source to drain mean for nagative volt input is source and output is drain

n channel mosfet logic low (vi) that mean mosfet not close circuit between the drain and source ,v_out you got vdd voltage via resistance . (Hi)
when you apply vi = Hi in N-Channel mosfet ,mean drain to source connected (close circuit) in this case you got v_out source low you can got at v_out .same way in P-channel but gate work reverse as n-channel mosfet work