XR2207 Exar Corporation, XR2207 Datasheet - Page 15

• Manufacturer Part Number: XR2207
• Description: Voltage-Controlled Oscillator
• Manufacturer: Exar Corporation

Duty Cycle Control
The duty cycle of the output waveforms can be controlled
by frequency shift keying at the end of every half cycle of
oscillator output. This is accomplished by connecting one
or both of the binary keying inputs (pins 8 or 9) to the
squarewave output at pin 13. The output waveforms can
then be converted to positive or negative pulses and
sawtooth waveforms.
Figure 18 is the recommended circuit connection for duty
cycle control. Pin 8 is shorted to pin 13 so that the circuit
switches between the “0,0” and the “1,0” logic states
given in Table 1 . Timing pin 5 is activated when the output
is “high,” and the timing pin is activated when the
squarewave output goes to a low state.
The duty cycle of the output waveforms is given as:
Rev. 2.02
f
CR
1
3
1
R
R
C
3
1
V
V
C
T
Figure 17. Frequency Sweep Operation, Single Supply
1 F
Sweep or FM input
VC-
1 F
10
8
9
VC
RC
A
B
GND
VC+
V+
V
CC
1
R1
XR-2207
V
C1
15
4
T
R2
2
R3
and can be varied from 0.1% to 99.9% by proper choice of
timing resistors. The frequency of oscillation, f, is given
as:
The frequency can be modulated or swept without
changing the duty cycle by connecting R
common control voltage V
Figure 15 ).
waveforms are shown in Figure 19 .
5
C
R3
6
R4
C2
3
7
SWO
TWO
BIAS
V-
1 F
12
Duty Cycle
f
13
14
11
V
The sawtooth and the pulse output
C
3.9K
2
EE
R
V
Vbias
CC
2
4.7K
1
R
3
R
1 F
2
Triangle Wave
R
C
Square Wave
2
, instead of V
R
Output
Output
3
XR-2207
5.1K
2
and R
V
EE
CC
3
(see
to a