Intel 820E Benutzerhandbuch

Design Guide 

 

187 

1.8 V

2.5 V

diode_1.8V&2.5V

 

The V

DDQ

 plane is used to power the MCH AGP interface and the graphics component AGP interface. 

Refer to the AGP Interface Specification, Revision 2.0 (

For long-term component reliability, the following power sequence is strongly recommended while the 
AGP interface of the MCH is running at 3.3 V. If the AGP interface is running at 1.5 V, the following 
power sequence recommendations no longer apply. The power sequence recommendations are as 
follows: 

1.  During the power-up sequence, the 1.8 V must ramp up to 1.0 V before the 3.3 V ramps up to 

2.2 V. 

2.  During the power-down sequence, the 1.8 V cannot ramp below 1.0 V before the 3.3 V ramps 

below 2.2 V. 

3.  The same power sequence recommendation applies when entering and exiting the S3 state, because 

MCH power is completely off during the S3 state.  

System designers must keep this requirement in mind while designing the voltage regulators and 
selecting the power supply. For further details regarding the voltage sequencing requirements, refer to the 
latest revision of the Intel

Note:  This regulator is required in all designs (unless the design does not support 1.5 V AGP, and therefore 

does not support 4

×

 AGP). 

The 3.3 V

SB

 plane powers the I/O buffers in the resume well of the ICH2 and the PCI 3.3 V

AUX

 suspend 

power pins. The 3.3 V

AUX

 requirement states that during suspend, the system must deliver 375 mA to 

each wake-enabled card and 20 mA to each non-wake-enabled card. During full-power operation, the 
system must be able to supply 375 mA to each card. Therefore, the total current requirement is as 
follows: 

• 

Full-power operation: 375 

mA 

×

 number of PCI slots 

• 

Suspend operation: 

(375 + 20) 

×

 (number of PCI slots – 1) 

In addition to the PCI 3.3 V

AUX

, the ICH2 suspend well power requirements must be considered, as 

shown in Error! Reference source not found..  

Note:  This regulator is required in all designs.