AS1331
Datasheet - Application Information
9 Application Information
Component Selection
Only three power components are required to complete the design of the buck-boost converter. For the adjustable
version VOUT programming resistors are needed. The high operating frequency and low peak currents of the AS1331
allow the use of low value, low profile inductors and tiny external ceramic capacitors.
Inductor Selection
For best efficiency, choose an inductor with high frequency core material, such as ferrite, to reduce core losses. The
inductor should have low DCR (DC resistance) to reduce the I²R losses, and must be able to handle the peak inductor
current without saturating. A 6.8µH inductor with a >600mA current rating and <400mΩ DCR is recommended.
Table 4. Recommended Inductors
Part Number
LPS3015-682M
EPL2014-682M
XPL2010-682M
L
DCR
Current Rating Dimensions (L/W/T)
Manufacturer
Coilcraft
www.coilcraft.com
6.8µH
6.8µH
6.8µH
300mΩ
287mΩ
336mΩ
0.89A
0.80A
0.73A
3.0x3.0x1.5mm
2.0x2.0x1.4mm
2.0x1.9x1.0mm
Capacitor Selection
The buck-boost convertor requires two capacitors. Ceramic X5R or X7R types will minimize ESL and ESR while
maintaining capacitance at rated voltage over temperature. The VIN capacitor should be at least 2.2µF. The VOUT
capacitor should be between 10µF and 47µF. A larger output capacitor should be used if lower peak to peak output
voltage ripple is desired. A larger output capacitor will also improve load regulation on VOUT. See Table 5 for a list of
capacitors for input and output capacitor selection.
Table 5. Recommended Input Capacitor
Part Number
C
TC Code Rated Voltage Dimensions (L/W/T)
Manufacturer
Murata
www.murata.com
GRM188R61A225KE34
GRM188R60J475KE19
GRM219R60J106KE19
2.2µF
4.7µF
10µF
X5R
X5R
X5R
10V
6.3V
6.3V
0603, T=0.87mm
0603, T=0.87mm
0805, T=0.95mm
Table 6. Recommended Output Capacitor
Part Number
C
TC Code Rated Voltage Dimensions (L/W/T)
Manufacturer
Murata
www.murata.com
GRM21BR61A106KE19
GRM319R61A106KE19
GRM319R61A106KE19
GRM31CR61C226KE15
GRM31CR60J475ME19
10µF
10µF
10µF
22µF
47µF
X5R
X5R
X5R
X5R
X5R
10V
10V
10V
16V
6.3V
0805, T=1.35mm
1206, T=0.95mm
1210, T=0.95mm
1206, T=1.8mm
1206, T=1.75mm
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