XR-2209 Datasheet, PDF (6/20 Pages) Exar Corporation – Voltage-Controlled Oscillator

XR-2209
V_CC
V_CC
S2
I+ C
1mF
R_L
12
V_CC C 1
3
C 2 _SWO ⁷
XR-2209
TWO ⁸
BIAS ⁵
Square Wave
Output
Triangle Wave
Output
TR
V_EE
D1
4
6
10K
1mF
R
S1
V_EE
I-
V_EE
1mF
Figure 4. Test Circuit for Split Supply Operation
OPERATING CONSIDERATIONS
Supply Voltage (Pins 1 and 6)
The XR-2209 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 6)
For split supply operation, this pin serves as circuit
ground. For single supply operation, pin 6 should be ac
grounded through a 1mF bypass capacitor. During split
supply operation, a ground current of 2 I_T flows out of this
terminal, where I_T is the total timing current.
Bias for Single Supply (Pin 5)
For single supply operation, pin 5 should be externally
biased to a potential between V_CC/3 and V_CC/2V (see
Figure 3.) The bias current at pin 5 is nominally 5% of the
total oscillation timing current, I_T.
Bypass Capacitors
The recommended value for bypass capacitors is 1mF
although larger values are required for very low frequency
operation.
Timing Resistor (Pin 4)
The timing resistor determines the total timing current, I_T,
available to charge the timing capacitor. Values for the
timing resistor can range from 2kW to 2MW; however, for
optimum temperature and power supply stability,
recommended values are 4kW to 200kW (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.
Rev. 2.02
6