MB3785A Datasheet, PDF (19/29 Pages) Fujitsu Component Limited. – Switching Regulator Controller (4 Channels plus High-Precision, High-Frequency Capabilities)

MB3785A
s METHOD OF SETTING THE TRIANGULAR-WAVE OSCILLATOR CIRCUIT
1. When Not Using Ceramic Resonator
Connect the OSCIN terminal (pin 14) to GND and leave the OSCOUT terminal (pin 15) open. This makes it possible
to set the oscillation frequency with only CT and RT.
Figure 7. When Not Using Ceramic Resonator
OSCIN OSCOUT RT
CT
14
15
16
17
Open
RT
CT
2. When Using Ceramic Resonator
By connecting a ceramic resonator between OSCIN and OSCOUT as shown below, you can set the oscillation
frequency. In this case, too, CT and RT are required. Determine the values of CT and RT so that the oscillation
frequency of this RC network is about 5-10% lower than that of the ceramic resonator.
Figure 8. When Using Ceramic Resonator
OSCIN OSCOUT RT
CT
14
15
16
17
Ceramic resonator
RT
CT
C1
C2
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