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Additional Circuits
The purpose of the IC1704 MMV at pins 9-5 and the comparator at IC1705/
pins 2-5 is to provide an operating window for the low output pulse leaving
this stage at CN1303/pin 9. The output pulse can only go low within this
window. This prevents a double pulse that could be caused by local noise
and the danger of shutting off the H. Output transistor early after turn on.
Operating Window Circuit
Device
Input
MMV
IC1704/pin 9
Comparator
IC1705/pin 10
Comparator
IC1705/pin
The scope shot shows the H. drive signal input IC1704/pin 2 and output of
the first MMV (ch 1, 2) which triggers the second MMV, closing the window.
The second MMV output is shown in the last waveform (ch 4). It is reset at
the end of its timing by the inhibit pulse applied to IC1704/pin 11 (ch 3).
After being reset, the window is opened, permitting the main output pulse
from IC1705/pin 1 to occur and leave CN1303/pin 9.
Output
Purpose
IC1704/pin 5
Creates an
operating
window pulse.
IC1705/pin 13
Makes a low
pulse to end
the window
pulse.
IC1705/pin
Inverter
99
P M 3 3 9 4 , F L U K E & P H I L I P S
c h 1
c h 2
1
c h 3
c h 4
2
3
C H 1 ! 5 . 0 0 V =
C H 2 ! 5 . 0 0 V =
4
C H 3 ! 5 . 0 0 V =
C H 4 ! 5 . 0 0 V =
W a v e f o r m H D 1 a – O p e r a tin g W in d o w
N a m e
C h a n n e l 1
H . D r iv e
s t
C h a n n e l 2
1
M M V O u t p u t
C h a n n e l 3
In h ib it/ r e s e t p u ls e
n d
C h a n n e l 4
2
M M V O u t p u t
T im e b a s e
T
B W L
P K D
C H P M T B 1 0 . 0 u s - 1 . 4 6 d v c h 1 +
L o c a t io n
IC 1 7 0 4 / p in 2
IC 1 7 0 4 / p in 1 3
IC 1 7 0 4 / p in 1 1
IC 1 7 0 4 / p in 5
1 0 u s e c / d iv
V o lt a g e /d iv
5 V p - p
5 V p - p
5 V p - p
5 V p - p
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