– 11 –
ASIC,
memory
CCD
8bit
CPU
LCD
MONITOR
Power supply voltage
Power OFF
Playback mode
Shooting
USB connection
1.20 V, 3.25 V
13 V, -7.5 V
3.5 V
3.2 V
3.25 V
OFF
OFF
32 KHz
OFF
ON
OFF
32 MHz
ON
ON
ON
32 MHz
ON
ON
OFF
32 MHz
OFF
Table 5-3. Power supply control
4. Power Supply Control
The 8-bit microprocessor controls the power supply for the overall system.
The following is a description of how the power supply is turned on and off. When the battery is attached, IC501 is operating and
creating 3.8 V, a regulated 3.2 V voltage is normally input to the 8-bit microprocessor (IC301) by IC302, clock counting and key
scanning is carried out even when the power switch is turned off, so that the camera can start up again.
When the power switch is off, the 8-bit microprocessor operates 32.768 kHz of clock.
When the battery is removed, the 8-bit microprocessor power switches the lithum secondary battery for memory backup by
IC302, and operates at low consumption. At this condition, operates 32.768 kHz clock counting by clock.
Also, the battery for backup is charged 10 hours from it to be attached.
When the power switch is on, the 8-bit microprocessor starts processing. The 8-bit microprocessor first sets the PON signal at
pin (30) to High, and then turn on the power circuit. After PON signal is to High, sets external port of ASIC after approximately
100 ms. According to setting of this external port, carry out setting of the operating frequency and oscillation control in the ASIC.
Also, it starts communication with ASIC, and confirms the system is operative.
When the through image is operating, set the PAON-PAON4 signals (ASIC) to High and then turn on the CCD. When the through
image is playing, set the PAON-PAON4 signals to Low and then turn off the CCD. When LCD panel turns on, set BL ON signal at
pin (41) to High, and turn on the backlight power.
When the power switch is off, the lens will be stowed, and PON, PAON-PAON4 and BLON signals to Low and the power supply
to the whole system is halted. The 8-bit microprocessor set operation mode of clock ocillation (32.768 kHz).
Table 5-2. Key Operation
3. Key Operaiton
For details of the key operation, refer to the instruction manual.
1
2
0
1
2
3
SCAN
OUT
SCAN
IN
UP
-
TELE
PW_TEST
LEFT
WIDE
-
RIGHT
SCENE
MENU
0
TEST
DOWN
4
SET
PLAY
-
5. Backlight Energy Saving Control
This model is equipped with a control function for switching the appearance of the LCD in accordance with the intensity of
external light in order to save power. The luminance sensor Q1905 detects the intensity of external light, and the results are A/D
converted and compared with the threshold value inside the microprocessor (pin (50) of IC301) in order to switch the lightness or
darkness of the backlight.
Brighter external light -> Brighter backlight (estimated normal outdoor level)
Darker external light -> Darker backlight (estimated normal indoor level)
Furthermore, there are two threshold values for light -> dark and dark -> light, and stable switching is maintained because of the
hysteresis between the two.
Switching of the backlight luminance is carried out by changing the PWM duty from the microprocessor (pin (40) of IC301) so that
the backlight LED current detection signal is added together with the feedback signal from the backlight illumination circuit (pin
(42) of IC501) to vary the current value for the LED.
