Motherboard Power On Sequence

Motherboard voltage and power-on power on principle MB POWER explain Motherboard work three elements  Voltage  frequency  RESET

** The voltage on the motherboard has +12V、-12V、+5V、-5V、 +3V、+5VSB、+3VSB、+1.5VSB +1.5VSB、+3V_DUAL、2.5V_DUAL、VCORE、ect. ** The ATX power supply, which is the motherboard power supply, is only available + 12V, -12V, + 5V, -5V, 5V, + 3.3V, + 5VSB V Kind of voltage, PWM conversion circuit, on the motherboard + 5VSB + 3VSB is a typical linear regulator circuit. ** The VCORE part is the most basic application of PWM technology, more complex Miscellaneous

+ 12V: Pin3,4 To be used to give CPU Vcore Vc Part of the power supply GND: Pin1,2

**PSON#**  PSON # is the low active signal, when this signal is Low, Power Supply voltage + 3.3V, + 5V, -5V, +12 V, -12V and so on. When this signal is pulled High, Power Supply stops sending Surface voltage. • Use this signal to design the "Soft Power down" shutdown function When the user shuts down the operating system under the command You can close all applications and use this pin's functions to auto-close Machine movement. • Pull this signal up to + 5VSB on the mainboard. • When the User presses the Power Button, the Super I / O will be issued This signal is pulled low, thereby informing Power Supply of the power supply.

** PWROK ** PWROK is the power-ready OK signal. When the power is supplied + 3.3V And + 5V to 95% of the Normal value, by the Power Supply Send this signal. When + 3.3V or + 5V falls below the Normal value, Supply will pull this signal low. When the motherboard receives this signal, that power is ready to start, you can start action. However, in most cases, we will not use this signal to notify the motherboard But use a dedicated ASIC to detect +3.3 V and +5 V power Pressure, issued by the ASIC when the voltage issued by the power supply meets the requirements The PWROK signal notifies the motherboard of the action AS016, W83627EHF and so on. ?? This PIN is generally empty on the motherboard.

** +5VSB ** + 5VSB: Standby power provides power down state Under the motherboard needs a variety of voltage, including: Standby and Dual Power. ATX provides the current not less than 10mA, but the current motherboard To provide USB device startup, recapture and other functions, requires a lot of current. General Power supply can provide about 2A. Tolerance: + 5V ± 5% Need to use stand by power include: Super I / O, South Bridge, LAN chip, etc .. In S3 state, in addition to the above part need To be outside the memory required + 2.5V dual.

** +3.3V ** There are many places on the motherboard that need + 3.3V. + 3.3V is generally the latest from the Power Supply of the supply. General power supply 5A or so of current. Tolerance: + 3.3V ± 4%

** ±5V ** 1. IO on the motherboard almost all use +5 V, such as: KB & MS, USB, F_PANEL, etc. Also provided to the IO controller Super I / O. 2. -5V is now rarely used when we encounter mainly GD75232 core On-chip connection for COM PORT.

** ±12V ** 1. +12 V available to Vcore (P4 & K8 use, K7 use 5V to Vcore power supply). 2. +12 V available to PCI slot, AGP slot, COM chip, FAN Power and so on. 3.-12V available to the PCI slot and COM chips. The following first describes the motherboard power

** + 3V_Dual effect ** 1. Mainly used to convert into 2.5V_Dual. 2.Suspend LED 3.Clock Generator

** +2.5V_Dual ** 1. Available for memory and northbridge part of the memory interface part, for K8 The memory controller is integrated in the CPU. 2. Generally by +3 V_Dual be. 3. Software to adjust the voltage: There are two ways to adjust the voltage of 2.5V_Ref, The second is to adjust the feedback voltage.

** +5V_DUAL ** Used to wake up

** + 2.5V Dual Reference Voltage Typical Circuit **

** +2.5V ** + 2.5V voltage directly from the +2.5 V_Dual through a MOS switch to provide, Use + 12V as the MOS gate control to ensure entry into S3 (standby) + 2.5V can be turned off to avoid leakage.

** GMCH_VTT ** GMCH_VTT is provided to the Northbridge FSB.

Typical Circuit

** + 5VA typical circuit ** + 5VA to provide AUDIO part.LM78L05 is a three-terminal regulator, The internal use of linear transformer method, the output voltage is fixed. Can be isolated +12 V interference.

** GND&GNDA** 1.GND: ground signal. Signal reference. 2.GNDA: Audio part of the ground signal. 3. The difference between the two: GND is the digital ground (ie digital signal reference GNDA is the analog ground (ie, the reference level of the analog signal) The threshold level of the digital circuit is high, while the analog signal design is weak , So the higher the GNDA requirements. 4 circuit to achieve: the general is to connect the two together through the inductor, but now In order to cost down, through the PCB internal short to achieve.

** Power-on principle to explain **

** The SIS power-on principle is described as follows: 1. PWRBTN # signal is sent when the power is on. 2.ICH received after the issue of SLP_S3 # SUSB # SUSC # 3.SUPER I / O or ASIC received after the power to a PSON # 4. At this point the power issue +5 / -5 +3 +12 / -12 to the entire motherboard 5. At the same time SUPER I / O or ASIC receive +5 / -5 +3 +12 / -12 6.SUPER I / O or ASIC after receiving the same time issued POWER OK To ICH and GMCH 7. At this time ICH issued RESET, issued to GMCH called PCIRST # 8. When the GMCH meets the operating conditions, issue CPURST # and POWERGOOD 9. Corresponding to the CPU after receiving the start work.

** RETURN

INTEL power principle with SIS power principle is only one of the most important difference INTEL is the CPU POWER GOOD ICH issued. The SIS POWER GOOD signal is GMCH issued. Power - on princ Startiple

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START TT

TRIGGER

When the + 3.3V and + 5V of the power supply are up to 95% of NORMAL, This signal is sent by POWER SUPPLY, usually detected by ASIC +3.3, +5 voltage, when in line with the signal from the ASIC POWEROK Know the board action. Have this function ASIC AS016 (16pin small core Chip), W83627EHF and so on.