ANP015 Datasheet, PDF (13/15 Pages) List of Unclassifed Manufacturers – Application Note AP2011 High Efficiency Synchronous PWM Controller

Application Note
AP2011 High Efficiency Synchronous PWM Controller
ANP015
Preliminary
z Output P-channel MOSFET and N-channel MOSFET Selection
A. The current ability of the output P-channel and N-channel MOSFETs must be at least larger than the
peak switch current IPK. The voltage rating VDS of the P-channel and N-channel MOSFETs should be
at least 1.25 times the maximum input voltage.
B. The MOSFETs must be fast (switch time) and must be located close to the AP2011 using short leads
and short printed circuit traces. In case of a large output current, we must layout a copper to reduce the
temperature of these two MOSFETs.
Because of their fast switching speed and low DS(ON) resistor (RDS(ON)), the Anachip AF44XX series
provide the best performance and efficiency, and should be the first choice, especially in low output
voltage applications.
z Input Capacitor Selection
A. The RMS current rating of the input capacitor can be calculated from the following formula table. The
capacitor manufactured by data sheet must be checked to assure that this current rating is not
exceeded.
Calculation
δ
I PK
Im
∆ _IL
I IN (rms)
Step-down (buck) regulator
Ton/(Ton+Toff)
I I^− LOAD(max)
LOAD (min)
I I⁺ LOAD(max)
LOAD (min)
I ^{2 ×} LOAD(min)
δ
×
⁽I
PK
×
I
)+
m
1
3
(∆
I
)²
L


B. This capacitor should be located close to the IC using short leads and the voltage rating should be
approximately 1.5 times the maximum input voltage.
Anachip Corp.
www.anachip.com.tw
13/15
Rev. A.0 Oct, 29, 2004