XR-2209
12
Rev. 2.02
R
L
Square Wave
Output
Triangle Wave
C
1F
TR
46
BIAS
5
TWO
8
SWO
7
C2
3
C1
21
XR-2209
R
Output
1F
5.1K
5.1K
Figure 14. Single Supply Operation
V
CC
V
CC
V
CC
V
CC
V
EE
Single Supply Operation
The circuit should be interconnected as shown in
Figure 14
for single supply operation. Pin 6 should be
grounded, and pin 5 biased from V
CC
through a resistive
divider to a value of bias voltage between V
CC
/3 and
V
CC
/2.
The frequency of operation is determined by the timing
capacitor C and the timing resistor R, and is equal to
1/RC. The squarewave output is obtained at pin 7 and
has a peak-to-peak voltage swing equal to the supply
voltage. This output is an “open-collector” type and
requires an external pull-up load resistor (nominally 5k)
to V+. The triangle waveform obtained at pin 8 is centered
about a voltage level V
O
where:
V
O
+
V
B
)
0.6V
where V
B
is the bias voltage at pin 5. The peak-to-peak
output swing of triangle wave is approximately equal to
V
CC
/2.
Frequency Control (Sweep and FM) - Split Supply
The circuit given in
Figure 15
shows a frequency sweep
method for split supply operation.
The frequency of operation is controlled by varying the
total timing current, I
T
, drawn from the activated timing pin
4. The timing current can be modulated by applying a
control voltage, V
C
, to the timing pin through a series
resistor R. As the control voltage becomes more
negative, both the total timing current, I
T
, and the
oscillation frequency increase.
The frequency of operation, is now proportional to the
control voltage, V
C
, and determined as:
f
+
1
RC
ƪ
1 )
V
C
R
R
C
V
EE
ƫ
Hz
