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 .