APW7311 データシートの表示（PDF） - Anpec Electronics
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APW7311 Datasheet PDF : 16 Pages
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APW7311
Application Information
Setting Output Voltage
The regulated output voltage is determined by:
VOUT= 0.925× (1 + R1 ) ⋅ (V)
R2
To prevent stray pickup, please locate resistors R1 and
R2 close to APW7311.
Input Capacitor Selection
Use small ceramic capacitors for high frequency
decoupling and bulk capacitors to supply the surge cur-
rent needed each time the N-channel power MOSFET
(Q1) turns on. Place the small ceramic capacitors physi-
cally close to the VIN and between the VIN and GND.
The important parameters for the bulk input capacitor are
the voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and
current ratings above the maximum input voltage and
largest RMS current required by the circuit. The capacitor
voltage rating should be at least 1.25 times greater than
the maximum input voltage and a voltage rating of 1.5
times is a conservative guideline. The RMS current (I )
RMS
of the bulk input capacitor is calculated as the following
equation:
IRMS = IOUT D × (1 − D) ⋅ (A)
where D is the duty cycle of the power MOSFET.
For a through hole design, several electrolytic capacitors
may be needed. For surface mount designs, solid tanta-
lum capacitors can be used, but caution must be exer-
cised with regard to the capacitor surge current rating.
T=1/FOSC
VLX
DT
IL
IQ1
ICOUT
I
IOUT
I
VOUT
IOUT
VOUT
Figure 1. Converter Waveforms
In critical condition, like input voltage plug in, it will cause
the high spike voltage. It is recommended to place large
capacitance and higher voltage rating to reduce the spike
voltage. In general, to parallel an aluminum electrolytic
capacitor with large capacitance can reduce the spike volt-
age in critical condition. This aluminum electrolytic ca-
pacitor must also be short pin wire to make it as close
as to the power plane or trace.
VIN
C I N1
C I N2
10 µF/
MLCC
VIN
AWP 7311
IQ1
Q1
Q2
VIN
VIN
CIN
IL
LX L
ICOUT
IOUT
ESR
VOUT
COUT
Copyright © ANPEC Electronics Corp.
8
Rev. P.1 - Jan., 2013
www.anpec.com.tw
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