Service Manual
After going through the filter and protection circuit, the 13.6V power supply will power external devices
via the expansion interface. The current may be up to 1A. For the 9V3A power supply, it is supplied by
U821, and output by ADJ with current up to 1A. It is used to power part of the exciter, RX and baseband
circuit. The U821 output control pin is valid at low level, and is grounded. It can output 9.3V power after
power-on. As for U807, it receives 9V3A power and outputs 5V power, which powers the D/A conversion
chip and power management IC (U806). U806 supplies power (3V3A) for CODEC chip (U501). The
U807 output control pin is valid at high level. It can output 5V power after power-on.
U801 is a DC-DC chip with adjustable output. After receiving 13.6V power, it will output 5VD power,
which supplies U803 and USB with 5V power. U803 is a PMU chip. It has 3 DC-DC output pins and 2
LDO output pins. U803 is configured by OMAP via the I
2
C interface. Description of DC-DC pins is shown
below:
1) DC-DC1 is controlled by U803 (PIN10). When the level is 0/1, the DC-DC1 output will be 3V/3.3V.
The maximum current is 1.2A.
2) DC-DC2 is controlled by U803 (PIN32). When the level is 0/1, the DC-DC2 output will be 1.8V/2.5V.
The maximum current is 1A.
3) DC-DC3 is controlled by U803 (PIN1). It can output 1V6D power. The maximum current is 900mA.
6.2.3 Reset
When the system is powered on, PMU will generate a reset signal “PWR_RST” to reset RX OMAP and
TX OMAP. When the system works abnormally, the watchdog will generate a 220ms reset signal as well.
See the following figure:
OUT_TX-RST
CODEC_RST
OUT-RST
Figure 6-7 System Reset Block Diagram
12
To Next Page
Loading...
