3A OUTPUT PROGRAMMABLE
POWER OSCILLATOR
TC96C555
APPLICATIONS
(Cont.)
Duty Cycle vs. Charge Current
Frequency in kHz
100
16
38
50
38
16
1
By connecting both resistors, R
CHG
and R
DIS
, to a
voltage source instead of connecting to the 4V reference of
Pin 3, one can increase or decrease the output frequency.
Increasing the voltage source to 5V will double the oscillator
frequency by doubling the voltage across both R
CHG
and
R
DIS
. Decreasing the voltage source to 3.5V will drop the
frequency in half.
2
3
4
80
Duty Cycle in %
60
Voltage Controlled Oscillator
RCHG = 51k, Rdis = 25.5k
1000K
40
100K
20
10pF
100pF
Frequency in Hz
10K
1000pF
0
10
20
30 40 50 60 70
Charge Current in
µA
ISINK = 100µA
80
90 100
1K
0.01µF
Figure 6. Duty Cycle vs. Charge Current
100
0.1µF
+12V
10
3.25V
3.5V
4V
Control Voltage
5V
7V
Figure 8. Frequency vs Control
.1µF
5
6
7
8
CONTROL
VOLTAGE
SOURCE
3
RCHG
VREF
VDD
OUT
OUT
VR1
TC96C555
7
OUTPUT
4
6
2
RDIS
C
VIN
1
VR2
GND
Figure 7. Voltage Controlled Power Oscillator
8
TELCOM SEMICONDUCTOR, INC.
4-167
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
