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1 Hardware Overview 1.5 Power Supply
1.5 Power Supply
The power supply supplies seven different voltages to the system board and performs the
following functions:
1. A/D conversion
The EC uses 10-bit sampling for A/D conversion to determine the following values:
• AC adaptor current
• Battery and temperature
2. AC adaptor and battery check
The EC checks the following by A/D converted values:
• Battery installed
The EC checks the following by GPIO values:
• AC adaptor connected
3. Abnormal check
The EC determines whether the condition is abnormal, and if so, stores an error code
into the error register.
4. Input port management
The EC monitors the following input signal status:
• System power ON/OFF status
• Direct CD power ON/OFF status
5. Beep and LED control
Beep is caused by the low battery status.
The EC controls the following two kinds of LED
DC IN LED (one color: green)
• Green = indicates AC adaptor is connected
Battery LED (two colors: orange and green)
• Green solid = The battery is fully charged.
1-14 Satellite P20-25 Series Maintenance Manual