Tektronix FG 5010 User Manual

Theory
of
Operation -
FG 5010
Charge
Pump
Charge
Pump is a
term that
applies
to a
bipolar
differen
tial current swich . With each applied pulse of voltage at one
set
of inputs
, the switch
will produce
a
current
pulse
of a
fixed
level .
Likewise , a pulse
applied
to
the other set
of in
puts
will
produce a like
current . These
pulses
of
current are
applied to
the
input summing
node of the
Lock Loop
Filter ,
along
with the
DIFFERENCE
VOLTAGE
signal from
the
Loop
1
circuits
.
The
Charge Pump is a tri
- state
device . Refer to Fig
. 4-18 ,
which
is a
simplified
diagram of the
Charge Pump
circuit .
When
either input
of U1720A is
high , it
indicates that the
Input
Trigger
signal is
leading the
SELECTED
SQWV
signal
or
that the
trigger
frequency
exceeds the
Main Loop
fre
quency
. At
the same
time ,
the inputs
to
U1720C
must
be
low
, so in this case
both of the
current paths
feed current to
the tie point of Q1822 and R1830 . This raises the voltage at
the
input of the
filter to about
+1.6 V. When
none of the
gate
inputs are high
, Q1830
conducts
and
Q1822 is cut
off ,
and
only half
of the
current is fed to the
node . When
either
4-40
FROM PHASE
DETECTOR
LOGIC ,
TRIGGER
SIDE
U1720A
+
12V
Q1820
STATES :
TRIGGER
LEADS SQWV : + 1.6V
NO SIGNAL LEADS : + 0.6V
SQWV LEADS TRICCER : -0.6V
Q1720
5mA
Q1822
Q1830
2000
THEVENIN
EQUIVALENT
OF R1826
AND R1825
+
input
of
U1720C
is
high , it
indicates
that
the
SELECTED
SQWV
signal is
leading the Input
Trigger
signal or
the loop
frequency
exceeds
the trigger
frequency
;
both
Q1822
and
Q1830 are
cut off ,
and the
voltage at
the
node is at
approxi
mately
0.6
V.
-0.6V
Each of
the
levels cause
the
driven circuit
, the
Lock
Loop
Filter , to act
in a
different way
. That is
, if the
trigger
leads
the
square wave ,
the voltage
at the node
is highest ,
and
the filter
capacitor
develops
a
negative ramp ;
if neither
signal
leads the
other , the
middle
voltage
is at the
node
,
and
the
capacitor
maintains
equilibrium ;
if
square
wave
leads
trigger , the
voltage at the
node
is
lowest ,
and the
ramp
is
positive .
It follows
that a
positive
ramp decreases
the
squarewave
signal frequency
, and
a negative
ramp causes
the
opposite
.
+
12V
>
Lock
Loop Filter
This circuit consists of two programmable integrators .
From
the
current
pulses
applied
, the
circuit
produces a volt
Q1722
5mA
Q1832
M
0,5mA OR 1 ØmA
Ø DIFFERENCE
VOLTAGE
FROM
LOOP
!
ㅑ
U1720C
Imm
Fig . 4-18 . Simplified diagram of Charge Pump .
FROM
PHASE
DETECTOR
LOGIC ,
SQUARE
-
WAVE
SIDE
} }
U18200
FILTERED
CONTROL
VOLTAGE
TO U1820C
3467-24
(
a )
U
U
U
U
U
U
U

Tektronix FG 5010 Specifications

General

Brand	Tektronix
Model	FG 5010
Category	Portable Generator
Language	English