XR-2209
6
Rev. 2.02
R
L
Square Wave
Output
Triangle Wave
S2
C
1F
I+
R
6
BIAS
5
TWO
8
SWO
7
C2
3
C1
21
XR-2209
S1
TR
Output
1F
I-
10K
D1
1F
Figure 4. Test Circuit for Split Supply Operation
V
CC
V
CC
V
CC
V
EE
V
EE
V
EE
4
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 1F 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 1F
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 2k to 2M ; however, for
optimum temperature and power supply stability,
recommended values are 4k to 200k (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.
