PRODUCT DATABOOK 1996/1997
SG1844/SG1845 Series
CURRENT-MODE PWM CONTROLLER
PRODUCTION DATA SHEET
APPLICATION INFORMATION
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.
VREF
RT
RT/CT
CT
GND
F ≈ 1.86 where RT ≥ 5kΩ
RTCT
FIGURE 12 — OSCILLATOR TIMING CIRCUIT
100K
47nF
10K
1K
100
1K
10K
100K
1M
Oscillator Frequency - (Hz)
FIGURE 13 — OSCILLATOR FREQUENCY vs. R FOR VARIOUS C
T
T
10
Copyright © 2000
Rev. 1.6c