04/04/2026
VDD_PLL at AVDD18_PLL, ano ang mga ito sa circuit line?
VDD = power supply / positive voltage rail
PLL = Phase-Locked Loop - ginagamit sa clock generation/frequency control
Ito yung voltage supply na nagpapagana sa clock generator ng IC (usually CPU or NAND controller)
Function ng PLL:
Nagge-generate ng stable clock signal
Kinokontrol ang:
CPU frequency
Data timing (lalo na sa NAND / memory)
Communication speed
Flow:
Main Power - PMIC - VDD_PLL - PLL Circuit - Clock Output - CPU / NAND
Kung walang VDD_PLL:
walang clock
walang boot
dead board / no power sequence
Kung may issue sa line na ito:
Bootloop
No NAND detection
No CPU activity
Stuck sa early power stage
Ang PLL hindi pwedeng maingay ang supply (noisy voltage), kaya nilalagyan ng ferrite bead resistor + capacitor para stable ang clock
AVDD18_PLL = 1.8V Analog Power Supply para sa PLL circuit
Ito ay:
dedicated analog supply ng PLL
mas sensitive sa noise
ginagamit sa:
oscillator
phase detector
loop filter
Bakit may AVDD at VDD sa PLL?
Dahil ang PLL ay mixed-signal circuit
Nahahati sa dalawang bahagi:
Digital Section
control logic
divider
feedback logic
powered by VDD
Analog Section
voltage-controlled oscillator (VCO)
phase detector
loop filter
powered by AVDD
Ang PLL parang may dalawang bahagi - digital para mag-compute, analog para gumawa ng actual na clock signal.
Flow:
PMIC - 1.8V Rail - AVDD18_PLL - PLL Analog Core - Stable Clock Output
Kapag may problema sa AVDD18_PLL:
Possible Symptoms:
No boot
No clock
NAND not detected
CPU is not running properly
Random restart / unstable
Testing Insight:
Expected:
around 1.8V stable
hindi nag fl-fluctuate
Pag may problema:
noisy voltage (nag jiggle sa multimeter)
low voltage (1.2V / 0.8V)
short to ground
Mas critical ang AVDD kaysa VDD sa PLL - kahit may VDD ka, pero noisy ang AVDD, wala pa ring stable clock.
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