Before pressing the power button, the system must generate its "Always-On" standby voltages. This is managed by a dual-channel PWM controller (typically a TPS51225 or equivalent).
The LA-C781P (ABL51) is a printed circuit board (PCB) designed for the HP Pavilion 15-af series. It is essential to correctly identify the motherboard to ensure compatibility and find the correct documentation. lac781p schematic top
Locate the PWM regulator responsible for +3VALW and +5VALW . The schematic provides the exact test points or inductor labels (e.g., PLxx ) where these voltages must be measured before the power button is pressed. Step 3: Analyzing the Power Sequence Before pressing the power button, the system must
: The gate voltage for the isolation MOSFETs must be driven approximately 6V higher than VIN (around 25V ) to fully turn on the N-channel gates via the charging IC’s ACDRV pump. 2. The Step-Down Section (3.3V & 5V Always-On) It is essential to correctly identify the motherboard
Located in the center-top region, the CPU is the heart of the board. The schematic highlights the extensive VCC_CORE power rails and nearby decoupling capacitors.
Based on similar naming conventions, the LAC781P is most likely one of the following:
If your regulator circuit fails, the internal block diagram guides diagnostics: