ESI VideoBridge 2150, Service Manual

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3 . 4 . 5 P owe r ON Rese t
R 34 410
R31
I ISK
Vee
R3S 410
+ C.S
R47
1 0
I
-SI I
I
�
I
1
� REF
I
EGR&
1
OPT
I
L
_ _
--.J
F i gure 3- 1 5 .
Power ON Re se t
The power ON r e s e t c i rc u i t ry i s n e c e s sa r y be c a u se o f t he l on g powe r-up
t i me o f t h e sw i t c h i n g powe r suppl y .
Du r i n g powe r- up , t h e ou t p u t o f
U 3 8 ( S Y S R S T ) i s a c t i v e L O . T h i s r e s e t s a l l l o g i c c i r c u i t r y a n d
m a i n t a i n s t h i s
t hen p rov i d e s a
l e v e l u n t i l V r e a c h e s 4 . 8
c c
s l i g h t t i me de l ay o f a bo u t
v o l t s . C a p a c i t o r C 5
1 / 1 0 se cond be f o re t h e
o u t p u t o f U 3 8 i s a l l owed t o g o H I a n d r e l ea s e t h e r e s e t l i n e . I f V c c
s ho u l d s u b s e q u e n t l y fa l l be l ow 4 . 5 vo l t s ( u s ua l l y d u e t o l i n e v o l tage
v a r i a n c e s ) , S Y S R S T w i l l a g a i n g o L O u n t i l V i s r e s t o r e d t o i t s
c c
ope ra t i n g l e v e l o f 4 . 8 v o l t s .
3 - 2 5
e l s l i 2 1 5 0 / 2 1 6 0 5 / 8 5