The working principle of APW7120 chip.

APW7120 chips are often used in the 965, G31, N68, N78 chipset motherboards produced by ASUS to control the generation of memory and bridge power.  

The memory power supply circuit controlled by the APW7210 chip is shown in figure 1.

 Fig. 1 A memory power supply circuit controlled by the APW7210 chip.

The working process of the memory power supply circuit controlled by the APW7210 chip is as follows.

 1. Use VCC5_DUAL to power U27 chip 5-pin through R351 current limit, and 1-pin power supply to 027 chip through D7.

2. After the short switch, the South Bridge chip sends out the SLP _ S5-high level, which is sent to the B pole of the Triode Q60 via the resistor R369, making the Q60 on, while the Q58 is cut off. U27 chip 7 feet through the chip internal pull up to more than 0.4V high level. After the VCC, BOOT, OCSET conditions are normal,

3. The U27 controls the drive signal from the 2-pin output on the tube Q49.

4. After the Q49 switch on, the VCC5_DUAL charges the inductor L22 and the back-stage capacitor, and slowly outputs V_DIMM power.

5. After Q49 on, the V_DIMM voltage will gradually rise. The resistors R332, R342 and R343 form the partial voltage circuit. The V_DIMM voltage is sampled and fed back to the 6-pin of the chip U27 for internal comparison.

6. When the voltage of the U27 chip 6 pin is higher than 0.8V, the U27 controls the 2-pin output signal so that the Q49 is turned off and Q53 is switched on from the 4-pin output signal.

7. Q53 turns on to form a closed loop, with the inductor L22 and the back-stage capacitor discharging the V_DIMM voltage to power the memory. The V_DIMM voltage drops slowly during discharge and returns to 6 feet after sampling resistance.

8. When the 6-pin voltage is less than 0.8V, the chip closes the lower Q53 and reopens the upper Q49 to charge.

9. Under the control of U27, Q49, Q53 cycle conduction by capacitor filter output smooth V_DIMM voltage to power the memory.

This article is from Allicdata Electronics Limited.