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- E4
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E5400 -
1-2. PW1 POWER SUPPLY CIRCUIT DESCRIP-
TION
1. Outline
The power supply circuit is mainly composed of the fol-
lowing blocks.
• Switching controller (IC501)
• Speed light control power supply, analog system pow-
er output (Q5101, T5001)
• Digital 1.8V power output (Q5131, L5131)
• Digital 3.3V power output (Q5141, L5141)
• LCD system power output (Q5151, L5151)
• Back light power output (Q5161, L5161)
• Lens drive power output (Q5171, T5002)
1-1. Switching controller (IC501)
This includes the 6 channels of basic circuits which are
necessary to control the power supply for the PWM-
type switching regulator. They are CH1 (digital 5.1V,
analog system power output), CH2 (digital 1.8V power
output), CH3 (digital 3.3V output), CH4 (LCD system
power output), CH5 (back light power output) and CH6
(lens drive system power output). Feedback from 5.0V
(D) (CH1), 1.80V (D) (CH2), 3.30V (D) (CH3), 12.0V
(L) (CH4) and lens drive 4.2V (CH6) are received, and
the PWM duty is varied so that each one is maintained
at the correct voltage setting level. For the LCD back
light power supply (CH5), feedback for the voltage at
both ends of output resistance is provided so that the
regular current can be controlled to be the current as set.
• Short-circuit protection circuit
If output is short-circuited for the length of time deter-
mined by the condenser which is connected to Pin (37)
of IC501, all output is turned off. The control signal (P
ON) are recontrolled to restore output.
1-2. Speed light control voltage, analog system pow-
er output
5.1V (VSB1), 15V (VSB2), 5.0V (A), 15.0V (A) and
-7.6V (A) are outputted. 5.1V (VSB1) is fed back to the
switching controller (IC501, Pin (40)) and is used for
PWM control.
1-3. Digital 1.8V power output
1.8V (D) is outputted. 1.8V (D) is fed back to the
switching controller (IC501, Pin (43)) and is used for
PWM control.
1-4. Digital 3.3V power output
3.3V (D) is outputted. 3.3V (D) is fed back to the
switching controller (IC501, Pin (45)) and is used for
PWM control.
1-5. LCD system power output
12.0V (L) is outputted. 12.0V (L) is fed back to the
switching controller (IC501, Pin (47)) and is used for
PWM control.
1-6. Back light power output
Regular current (18mA) is being transmitted to LED for
LCD back light. The voltage at both ends of the resis-
tance which is positioned in series with LCD is fed back
to the switching controller (IC501, Pin (2)) and is used
for PWM control.
1-7. Lens drive output
4.2V is outputted. 4.2V is fed back to the switching
controller (IC501, Pin (4)) and is used for PWM con-
trol.
