BD63536FJ 데이터 시트보기 (PDF) - ROHM Semiconductor
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BD63536FJ Datasheet PDF : 17 Pages
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BD63536FJ
Technical Note
●Switching regulator control
Fig. 18 shows the basic configuration of a switching regulator application. The error amplifier determines an output duty
cycle so that a voltage used to monitor output voltage will become equal to the internal reference voltage. The output driver
switches frequency at the said duty cycle, smoothes the switching voltage through the LC filter, and outputs Vout. This IC has
an internal reference voltage of 1.25V (typ) and a recommended output voltage range of 3.3V to 5V. Note that if the output
voltage is set to below 3.3V, for example to 1.25V, the output switching duty cycle may become narrow to disable current limit
setting, depending on oscillation frequency to be used.
VIN
VREF
OSC
VREG
OSC
UVLO
TSD
OVP
COMP
C.L.
COMP
GATE
OFF
Controller
Vcc
CS
GATE
Soft Start
GATEOFF
OVP
TSD
UVLO
IN-
FB
GND
Fig.18 Switching regulator block diagram
Typical filter circuit
When considering a filter circuit used to determine phase characteristics with the application of this IC, the three patterns
shown in Fig. 19 below are available as a popular way to arrange the filter circuits. The selective use of these circuits is
determined by the relationship between the PWM frequency to be used and the second pole of LC filter, the zero point at
ESR of output capacitor, and ripple elimination rate at the PWM switching frequency to be used.
(a) Filter example 1
(b) Filter example 2
(c) Filter example 3
Fig.19 Examples of filter circuits used to determine phase characteristics
The circuit (a) is the simplest pattern and available for use if the output capacitor has high ESR.
The circuit (b) is a pattern designed by adding a capacitor to the pattern of (a) and available for use if the output capacitor has
high ESR and the voltage ripple elimination rate at the PMW frequency needs to be increased from that of the pattern of (a).
The circuit (c) is a pattern designed by adding two zero-points and thereby available for use even if the output capacitor has
small ESR.
Selectively use the circuits according to the requirement specifications and situations for inductors, capacitors, and PWM
frequency using the patterns shown above.
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2009.11 - Rev.A
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