Table of Contents
Advertisement
3. Schematics
3-3.
Description of PWA Power
Circuit Operation
3-3-1.
Overview
The power circuit is primarily made up of the following blocks:
• Switching controller (IC501)
• 6 V power output (L5006 and Q5003)
• Digital 3.25 V power output (L5010)
• Digital 1.2 V power output (L5011)
• Analog power output (L5008 and Q5002)
• LCD backlight power output (L5007)
• EVF backlight power output (L5001 and Q5001)
• Motor 5.3 V power output (IC532, L5302 and Q5302)
Switching controller (IC501)
The basic circuits required for controlling the PWM-type
switching regulator power supply consist of 7 built-in
channels.
The channels are CH1 (6 V), CH2 (digital 3.2 V), CH3 (digital
1.2 V), CH4 (analog), CH5 (EVF backlight) and CH7 (LCD
backlight).
In response to feedback for the power output for the 6 V
system (CH1), VDD3 (CH2), VDD1.2 (CH3), analog systems
(CH4), EVF backlight (CH5) and LCD backlight (CH7), the
PWM duty is varied so that the respective voltages are at the
set values.
For the backlight power supply (CH5 and CH7), the end-to-
end voltage for the output resistance is used as feedback to
regulate the constant current so that the specified current is
maintained.
Short-circuit protection circuit
If output is short-circuited for an interval determined by the
capacitor connected to IC501 (pin 32), all output is turned off.
To recover operation, resend the control signal (P ON).
Analog power output
+13 V (A) and -7.5 V (A) are output.
The +13 V (A) output is fed back to the switching controller
(IC501 pin 48) to regulate the PWM.
Digital 3.25 V power output
VDD3 is output.
VDD3 is fed back to the switching controller (IC501 pin 23) to
regulate the PWM.
Digital 1.2 V power output
VDD1.2 is output.
VDD1.2 is fed back to the switching controller (IC501 pin 23)
to regulate the PWM.
EVF backlight power output
A constant current (5.1 mA) flows to the LCD backlight LED.
The end-to-end voltage for the resistance connected in series
with the LED is fed back to the switching controller (IC501
pin 45) to regulate the PWM.
3-4
Confidential: FUJIFILM Service Center Use Only
FinePix S5800/S800 Service Manual
LCD backlight power output
A constant current (27 mA) flows to the LCD backlight LED.
(A built-in timer and luminance sensor control the LCD PWM
and select the current value.)
The end-to-end voltage for the resistance connected in series
with the LED is fed back to the switching controller (IC501
pin 37) to regulate the PWM.
Motor 5.3 V power output
BOOST 5.3 V is output.
The BOOST 5.3 V output is fed back to IC532 pin 3 to
regulate the PWM.
Advertisement
Table of Contents
