OLIMEX© 2017
A20-OLinuXino-LIME2 user's manual
CHAPTER 5: CONTROL CIRCUITY
5. Introduction to the chapter
Here you can find information about reset circuit and quartz crystals locations, the power supply circuit is
also briefly discussed.
5.1 Reset
The board has hardware reset controlled by the AXP209 power system management IC.
It is a good practice to perform software reset of the board. Performing reset by disconnecting the power
supply might lead to software corruption of the operating system of choice.
5.2 Clocks
25 MHz quartz crystal Q1 is connected to pins X1 and X2 of the RTL8211CL Gigabit Ethernet controller.
32 768 Hz (RTC) quartz crystal Q4 is found at pins F1 and F2 of the A20 microcontroller.
24 MHz quartz crystal Q3 is found at pins N22 and N23 of the A20 microcontroller.
5.3 Power supply circuit
The power supply is handled mainly by AXP209 power management system, an Allwinner chip that goes
together with the A20 processor. It is mounted on the board but since it is relatively hard to find we also
sell it separately.
The power supply circuit of A20-OLinuXino-LIME2 requires input supply of 5V. The minimum wattage
is 2.5W, and this threshold may raise if using a lot of devices on the USB-HOST (via external hub), a lot
of GPIOs or you have a display connected to the LCD_CON or a hard disk powered from the
5V_SATA_PWR connector. If a discharged Li-Po battery is connected to the respective connector the
power consumption of the whole LIME2 board might rise enormously, since the built-in battery charger
would attempt to recharge it.
For more info on how to power the board refer to chapter “2.3 Powering the board”.
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