Samsung SF-830, Service Manual

Page: 121 / 189

3-2
CIRCUIT DESCRIPTION
Samsung Electronics
Repair Manual
3-2 Circuit Operation
3-2-1 CLOCK
1) System Clock
• KS32C61200 RISC PROCESSOR: drives PLL internally and uses 60MHz.
2) Video Clock
• Fvd =((PAPER 1SCAN LINE sending time * SCAN effective late /1SCAN LINE DOT #)*4
=(600dpi*600dpi*58.208mm/s*216mm*4)/(25.4mm*25.4mm*76.1%)=28.697MHz
•PAPER 1SCAN LINE sending time=SCAN LINE interval/DOCUMENT SPEED (58.208mm/S)
•1SCAN LINE DOT #=MAZ SCAN distance(216mm)*DOT# per 1mm
3)USB Clock
4)PM-22 Clock
3-2-2 POWER ON/OFF RESET
1) Signal Operation
• POWER ON/OFF DETECT VCC RISING/FALLING 4.5°
≠
4.6V
• Td=(Ct*V sensing)/I charge (...Ct=33µF, Is=100µA)
2) TIMING CHART
Device Oscillator
Frequency 20 MHz±%
Device Oscillator
Frequency 45.3928 MHz±%
Device Oscillator
Frequency 48 MHz±%
Device Oscillator
Frequency 66 MHz±%
Input Signal +5V Power Line (VCC)
Output Signal KS32C61200 nRESET 29F800B nRESET
RESET TIME (Td) 1.48~1.52ms
and SENSE V
CC
CC
CC
Threahold Voltage
V
CC
V
3.6V
RESET
t
d
Output
Undefined
Output
Undefined
V
2V
t
d