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1-3. PWA POWER CIRCUIT DESCRIPTION
1. Outline
This is the main power circuit, and is comprised of the follow-
ing blocks.
Switching controller (IC501)
Digital 3.25 V power output (L5002)
Digital 1.8 V power output (L5006)
Digital 1.2 V power output (L5003)
CMOS sensor 2.8 V power output (L5005)
LCD backlight power output (Q5007, L5007)
Motor system 5 V power output (L5301)
2. Switching Controller (IC501)
This is the basic circuit which is necessary for controlling the
power supply for a PWM-type switching regulator, and is pro-
vided with seven built-in channels, only CH1 (motor system),
CH2 (digital 3.25 V), CH3 (digital 1.2 V) and CH7 (LCD back-
light) are used.
Feedback from BOOST5V (CH1), VDD3 (CH2), VDD1.2
(CH3), LCD backlight (CH7) are received, and the PWM duty
is varied so that each one is maintained at the correct volt-
age setting level.
Feedback for the backlight power (CH7) is provided to the
both ends voltage of registance so that regular current can
be controlled to be current that was setting.
2-1. Short-circuit protection circuit
If output is short-circuited for the length of time determined
by the condenser which is connected to Pin (A6) of IC501, all
output is turned off. The control signal (P ON) are recontrolled
to restore output.
3. Digital 3.25 V Power Output
VDD3 is output. Feedback for the VDD3 is provided to the
swiching controller (Pin (F3) of IC501) so that PWM control
can be carried out.
4. Digital 1.2 V Power Output
VDD 1.2 is output. Feedback for the VDD 1.2 is provided to
the switching controller (Pin (C3) of IC501) so that PWM con-
trol to be carried out.
5. Backlight Power Supply output
Regular current (12mA) is being transmitted to LED for LCD
backlight. Feedback for the both ends voltage of registance
that is being positioned to in series LED are provided to the
switching controller (Pin (C4) of IC501) so that PWM control
to be carried out.
6. Motor System 5V Power Output
BOOST 5 V is output. Feedback for the BOOST 5 V is pro-
vided to the switching controller (Pin (B7) of IC501) so that
PWM control can be carried out.
7. Digital 1.8 V Power Output
+1.8 V (D) is output.
8. CMOS sensor 2.8 V Power Output
VAA 2.8 is output.
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