XR-2207 Datasheet, PDF (15/24 Pages) Exar Corporation – Voltage-Controlled Oscillator

XR-2207
ƪ ǒ Ǔƫ f
+
1
CR3
1
)
R3
RC
1
*
VC
VT
V_CC
V_CC
1µF
C
Square Wave
4.7K
Output
12
3
V+ C1
8A
C2
13
SWO
Triangle Wave
Output
9 _{B XR-2207}
10 _GND
TWO ¹⁴
BIAS ¹¹
Vbias
V_CC
5.1K
R1 R2 R3 R4 V-
1µF
4 5 6 7 12 3.9K
1µF
V_EE
V_T
1µF
RC
R3
VC-
VC+
VC
Sweep or FM input
Figure 17. Frequency Sweep Operation, Single Supply
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:
Duty
Cycle
+
R2
R2 ) 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:
ƪ ƫ f
+
2
C
1
R2 ) R3
The frequency can be modulated or swept without
changing the duty cycle by connecting R₂ and R₃ to a
common control voltage V_C, instead of V_EE (see
Figure 15). The sawtooth and the pulse output
waveforms are shown in Figure 19.
Rev. 2.02
15