Led Display Circuit - Toshiba e-STUDIO453 Service Manual

(4) Data Transmission
FRAME
240
LOAD
FRAME
LOAD
CP
D0-D3

5.4.2 LED display circuit

(1) Method of LED display
ex) Displaying "COPY" .
LDON0
Transistor is turned ON when the LDON 0 signal becomes "L" level.
Also, when IC pin changes to "L", the current flows from 5VL via the transistor to the LED ("COPY")
to turn ON the LED ("COPY").
Conditions to turn ON the LED
(a) The transistor (Q3) connected to the LED anode is ON.
(b) The output from the cathode side of the LED is "L" level.
The LED turns ON when the conditions (a) and (b) are met.
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/tF
 2 240
CP x(40/4) pulses
Fig. 5-404
5VL
Current
"L"
Q3
(COPY)
Fig. 5-405
5 - 11
/tF
 2 240
"L" 17
D7
G
R3
LED
IC
e-STUDIO350/352/353/450/452/453
 2
CONTROL PANEL
5