Tektronix FG 5010 User Manual

Theory
of
Operation -
FG 5010
the
charge pump
drive signal . The
result is
an output
pulse
that is
very little wider
than the
propagation
time of
U1720B
and the time difference between the two , thus containing
just
enough
energy
to
affect the
Charge
Pump
output
,
and
slightly
shift
the
frequency
.
As
illustrated
in Fig .
4-15
, the
resultant output of the circuit is a series of very narrow
pulses
that first
drive the Main Loop
slightly up
in frequency ,
then
slightly
down ,
averaging
to the
frequency
of
the
applied
trigger
signal .
Refer
to Fig . 4-16
, which
illustrates the case
that occurs
when the
trigger
signal
leads the
Main Loop signal
by a half
cycle , so
the
phase is
different
, and the
frequency
is
also
somewhat different . The first positive edge from the trigger
sets U1730B , which arms U1730A , begins the pump - up sig
nal
to
the Charge
Pump ,
and enables
U1720B
.
Before
the
next
positive edge
of the trigger
occurs , the square
wave at
pin
9 of
U1732A
sets the
latch
and
resets
both U1730B
and
U1732A
through the
output
of
U1720B
.
This
terminates
the
charge
pump
signal
.
TheLock
Loop
Filter
can respond
to
a
pulse of this
width , so
the Main Loop
frequency is
altered
upward
slightly . The
next
trigger positive
edge
again sets
U1730B , and the process is repeated . Note , though , that
the
pulsewidth
of the second charge
signal is
narrower , and
continues to decrease with succeeding cycles . Finally , the
Phase
- lock Loop
adjusts the
Main Loop
frequency to the
point
that the
SELECTED SQWV
positive edge
leads the
trigger
positive ,
indicating
that the
correction
process has
overshot the center mark . Then , the process is reversed ,
until the circuit rocks back and forth over the in - phase mark ,
as
just
explained .
4-38
TRIGGER
( U1730-9 )
SELECTED
SQWV
( U1732-9 )
U1720B
- 6
U1730B - 15
U1732A - 2
U1720A -
3
1
Refer to
Fig . 4-17
, which
illustrates
the
case that
occurs
when the
trigger
signal
is
more
than twice the
frequency
of
the
squarewave
signal
. In
theory ,
the inner
latches (
phase
detector
)
could cope
with this
magnitude of
disparity
in fre
quency ,
but
the
process
would be
slow ,
and
would
tempo
rarily
reverse
when
phase
crossings
occurred ,
such as
when
the
frequency
of
one
signal
was
twice
or
three
times
the
other
.
The
first positive
edge of the
trigger
signal
sets U1730B
,
which
arms
U1730A
to set
at the
next transition
if the
squarewave
signal
does
not arrive
first .
This
does
not occur ,
since
the trigger
signal is
more
than
three
times faster
than
the
square
wave , in
this case .
The second
positive
edge , at
t1
,
sets U1730A
; the
positive
level
at
U1720A pin
4 has
no
effect on
the gate
for now ,
since
the
other input is
already
high
from the set
state of
U1730B . At t2 , the
square - wave
signal
sets
U1732A
, which
resets
both of the
inner
latches .
This has
no
effect on
the
output of
U1720A
, which
is still
held by
input pin
4. At
t3 ,
inner
latch U1730B
is
once again
set
, and
in the
absence
of the
high
at
pin 7 ,
U1730A
is
reset .
Again , this
has no
effect
on the
output of
U1720A
,
since pin
5
rises
just
as pin
4 falls . At
t4 ,
U1730A sets
, having
been
enabled
to do so
by the
high
from
U1730B .
Both
latches
ignore
the positive
edge
that
occurs
at t5
, since
both
are
set
. At t6 , the positive
edge of
the square - wave
signal sets
U1732A , which
resets both
inner
latches again .
As
the
output of
U1720A
continues to stay
high , the
Phase
- lock Loop
continues
to
increase the frequency
of the
1
1
1
Fig . 4-15 . Phase Detector Logic signals at phase lock .
1
3467-21A
REV
JUL
1982
U
U
U
نال
U
U
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Tektronix FG 5010 Specifications

General

Brand	Tektronix
Model	FG 5010
Category	Portable Generator
Language	English