BD63536FJ Ver la hoja de datos (PDF) - ROHM Semiconductor
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BD63536FJ Datasheet PDF : 17 Pages
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BD63536FJ
Technical Note
○OSC: PWM oscillation frequency setting capacitance connection pin
The OSC pin is a pin used to produce a triangular waveform for output PWM oscillation frequency and connect an external
resistor and capacitor. By connecting the external resistor and capacitor to this pin, perform charge and discharge. Since H
level for a triangular waveform is 1.4V (typ) and L level is 1.0V (typ), a triangular waveform having an amplitude of
OSC0.4V (typ) is produced. The resistor determines a charge current, and the current is discharged inside the IC through
resistance of 5k (typ). However, at high frequencies in excess of several hundred kHz, OSC amplitude may exceed 0.4V
(typ) due to delay in the internal circuit. To operate the IC at high frequencies, pay careful attention to the frequencies. The
following section shows a characteristics table of capacitance when the external resistor is set to 30k. For example, when
the capacitor is set to 1000pF, frequency “f” will come to 91 [kHz].
Oscillation frequenOcySCvs周. C波a数paCcaitpaan特ce性characteristics
1000
R= 3 0 KΩ
100
10
1
10
100
1000
10000
100000
Cap容a量cit値an[pcFe] [pF]
Fig.15 Typical oscillation frequency characteristics
A calculation formula used to make oscillation frequency setting is shown below.
f
1
C(0.31R 1980) 2e 7
Note that the formula shown above is a reference formula for calculations in the setting range of 470p to 2200pF for the
capacitor and 30k to 100k for the resistor. On application boards, oscillation frequencies may be influenced by wiring capacitance
or the capacity of an oscilloscope used to monitor the frequencies and thereby calculated values may become different from
actual values. Consequently, make it principle to use this formula as a guide for making oscillation frequency setting.
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2009.11 - Rev.A
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