XR-2207 Datasheet, PDF (7/24 Pages) Exar Corporation – Voltage-Controlled Oscillator

XR-2207
V_CC
V_CC
S2
I+ C
0.1µF
12
3
Binary
8
A
Keying Inputs 9 _B
V+ C1
C2
XR-2207
10
GND
SWO ¹³
14
TWO
11
BIAS
R1 R2 R3 R4 V-
4 5 6 7 12
I-
R1 R2 R3 R4
RL
Square Wave
Output
Triangle Wave
Output
V_EE
0.1µF
S1
Figure 4. Test Circuit for Split Supply Operation
OPERATING CONSIDERATIONS
Supply Voltage (Pins 1 and 12)
The XR-2207 is designed to operate over a power supply
range of $4V to $13V for split supplies, or 8V to 26V for
single supplies. Figure 5 shows the permissible supply
voltage for operation with unequal split supply voltages.
Figure 6 and Figure 7 show supply current versus supply
voltage Performance is optimum for $6V split supply, or
12V single supply operation. At higher supply voltages,
the frequency sweep range is reduced.
Ground (Pin 10)
For split supply operation, this pin serves as circuit
ground. For single supply operation, pin 10 should be AC
grounded through a 1µF bypass capacitor. During split
supply operation, a ground current of 2I_T flows out of this
terminal, where I_T is the total timing current.
Bias for Single Supply (Pin 11)
For single supply operation, pin 11 should be externally
biased to a potential between V⁺/3 and V⁺/2V (see
Figure 3). The bias current at pin 11 is nominally 5% of the
total oscillation timing current, I_T.
Bypass Capacitors
The recommended value for bypass capacitors is 1µF
although larger values are required for very low frequency
operation.
Timing Resistors (Pins 4, 5, 6, and 7)
The timing resistors determine the total timing current, I_T,
available to charge the timing capacitor. Values for timing
resistors can range from 2kΩ to 2MΩ; however, for
optimum temperature and power supply stability,
recommended values are 4kΩ to 200kΩ (see Figure 8,
Figure 9, Figure 10 and Figure 11). To avoid parasitic pick
up, timing resistor leads should be kept as short as
possible. For noisy environments, unused or deactivated
timing terminals should be bypassed to ground through
0.1µF capacitors.
Timing Capacitor (Pins 2 and 3)
The oscillator frequency is inversely proportional to the
timing capacitor, C. The minimum capacitance value is
limited by stray capacitances and the maximum value by
physical size and leakage current considerations.
Recommended values range from 100pF to 100µF. The
capacitor should be non-polarized.
Rev. 2.02
7