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1-4. PW1 POWER CIRCUIT DESCRIPTION
1. Outline
This is the main PW1 power circuit, and is comprised of the
following blocks.
Switching controller (IC501)
Digital and LCD system and 5.0 V system power output
(L5005, Q5015, D5005, C5036, C5037)
Digital 3.3 V system power supply (L5002, Q5003, D5002,
C5018)
Digital 3.4 V system power supply (L5003, Q5009, D5004,
C5029)
Series regulator (IC502)
Digital 2.5 V system power supply (Q5007, C5025, C5026)
Analog system 5 V power supply (L5008, Q5020, D5006,
C5045)
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 four built-in channels, only CH1 (digital 3.3 V), CH3
(5 V system), CH2 (digital 3.4 V) and CH4 (analog system 5
V) are used. Feedback from 3.3 V (D) (CH1), 3.4 V (D) (CH2),
5 V (D) (CH3) and 5.0 V (A) power supply outputs are re-
ceived, and the PWM duty is varied so that each one is main-
tained at the correct voltage setting level.
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 (33) of IC501, all
output is turned off. The control signal (P ON, P(A) ON and
LCD ON) are recontrolled to restore output.
3. Digital 3.3 V Power Output
3.3 V (D) is output. Feedback for the 3.3 V (D) is provided to
the switching controller (Pins (1) of IC501) so that PWM con-
trol can be carried out.
4. Digital 3.4 V System Power Output
3.4 V (D) is output. Feedback is provided to the swiching con-
troller (Pin (12) of IC501) so that PWM control can be carried
out.
5. 5 V System Power Output
5 V (D) and 5 V (L) are output. Feedback for the 5 V (D) is
provided to the switching controller (Pin (25) of IC501) so
that PWM control can be carried out.
6. Series Regulator (IC502)
This is provided with one built-in channel. Digital 3.4 V is in-
put, and digital 2.5 V is output.
7. Digital 2.5 V System Power Output
2.5 V (D) is output. Feedback for the 2.5 V (D) is provided to
the Pin (7) of IC502. The current of Q5008 base is controled
so that the voltage of Q5008 collector is 2.5 V.
8. Analog 5 V System Power Output
5 V (A) is output. Feedback is provided to the swiching con-
troller (Pin (36) of IC501) so that PWM control can be carried
out.
