PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
C
URRENT
-M
ODE
PWM C
ONTROLLER
P
R O D U C T I O N
D
A T A
S
H E E T
A P P L I C AT I O N I N F O R M AT I O N
OSCILLATOR
The oscillator of the 1844/45 family of PWM's is programmed by
the external timing components (RT, CT) as shown in Figure 13.
V
REF
R
T
R
T
/C
T
C
T
GND
R
T
- ( )
100K
47
nF
F
0n
10
F
7n
4.
nF
10
nF
22
F
1n
F
2n
2.
10K
F
≈
1.86
R
T
C
T
where R
T
≥
5kΩ
1K
100
1K
10K
100K
1M
Oscillator Frequency - (Hz)
FIGURE 13
— OSCILLATOR FREQUENCY vs. R
T
FOR VARIOUS C
T
FIGURE 12
— OSCILLATOR TIMING CIRCUIT
10
Copyright © 2000
Rev. 1.4 4/00