AIC1642 데이터 시트보기 (PDF) - Analog Intergrations
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AIC1642 Datasheet PDF : 14 Pages
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EL = 1 L × Ipk 2
2
Power required from the inductor per cycle must
be equal or greater than
PL/fSW = (VOUT + VD − VIN) * (IOUT) * ( 1 )
fsw
In order for the converter to regulate the output.
When loading is over IOB, PFM controller oper-
ates in continuous mode. Inductor peak current
can be derived from
AIC1642
IPK= VOUT+VD−VSW− x*IOUT+ VIN−VSW* TON *1− x
VIN−VSW 2
2L
2
Valley current (Iv) is
IV = VOUT+ VD− VSW− x*IOUT− VIN−VSW* TON*1− x
VIN−VSW 2
2L
2
Table 1 Indicates resistance and height for each coil.
Power Inductor Type
Inductance
( µH )
22
DS1608
47
Coilcraft SMT Type
100
(www.coilcraft.com)
22
DO3316
47
47
Sumida SMT Type CD54
100
47
Hold SMT Type PM54
100
Hold SMT Type PM75
33
Rated Current
Resistance ( Ω )
(A)
0.10
0.7
0.18
0.5
0.38
0.3
0.08
2.7
0.14
1.8
0.25
0.7
0.50
0.5
0.25
0.7
0.50
0.5
0.11
1.2
Height
(mm)
2.9
5.2
4.5
4.5
5.0
Capacitor Selection
A poor choice for an output capacitor can result in
poor efficiency and high output ripple. Ordinary
aluminum electrolytic, while inexpensive may
have unacceptably poor ESR and ESL. There are
low ESR aluminum capacitors for switch mode
DC-DC converters which work much well than
general unit. Tantalum capacitors provide still bet-
ter performance at more expensive. OS-CON ca-
pacitors have extremely low ESR in a small size.
If capacitance is reduced, output ripple will in-
crease.
Most of the input supply is supplied by the input
bypass capacitor, the capacitor voltage rating
should be at least 1.25 times greater than a
maximum input voltage.
Diode Selection
Speed, forward drop, and leakage current are the
three main considerations in selecting a rectifier
diode. Best performance is obtained with Schot-
tky rectifier diode such 1N5819. Motorola makes
MBR0530 in surface mount. For lower output
power a 1N4148 can be used although efficiency
and start-up voltage will suffer substantially.
12
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