AS1337
Datasheet - Application Information
Component Selection
Only three power components are required to complete the design of the buck-boost converter, except the additional
two resistors for the voltage divider to set VOUT. The high operating frequency and low peak currents of the AS1337
allow the use of low value, low profile inductors and tiny external ceramic capacitors.
Inductor Selection
The inductor should have low ESR to reduce the I²R power losses, and must be able to handle the peak inductor
current without saturating. High-frequency ferrite core inductor materials reduce frequency dependent power losses
compared to less expensive powdered iron types, which result in improved converter efficiency.
A 4.7µH to 15µH inductor value with a >850mA current rating and low DCR is recommended. For applications where
radiated noise is a concern, a toroidal or shielded inductor can be used.
Capacitor Selection
A 10µF capacitor is recommend for CIN as well as a 22µF for COUT. Small-sized ceramic capacitors are recommended.
X5R and X7R ceramic capacitors are recommend as they retain capacitance over wide ranges of voltages and temper-
atures.
Output Capacitor Selection
Low ESR capacitors should be used to minimize VOUT ripple. Multi-layer ceramic capacitors are recommended since
they have extremely low ESR and are available in small footprints. A 1 to 10µF output capacitor is sufficient for most
applications. Larger values up to 22µF may be used to obtain extremely low output voltage ripple and improve tran-
sient response.
An additional phase lead capacitor may be required with output capacitors larger than 10µF to maintain acceptable
phase margin. X5R and X7R dielectric materials are recommended due to their ability to maintain capacitance over
wide voltage and temperature ranges.
Input Capacitor Selection
Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. Ceramic
capacitors are recommended for input decoupling and should be located as close to the device as is practical. A 4.7µF
input capacitor is sufficient for most applications. Larger values may be used without limitations.
Table 5. Recommended External Components
Name
CIN
Part Number
Value
10µF
22µF
Rating
6.3V
Type
X5R
X5R
Size
0805
0805
Manufacturer
Murata
www.murata.com
GRM219R60J106KE19
GRM21BR60J226ME39
COUT
6.3V
Coilcraft
www.coilcraft.com
L1
MOS6020-472ML
4.7µH
1.82A
50mΩ
6.8x6.0x2.4mm
PCB Layout Guidelines
The high-speed operation of the AS1337 requires proper layout for optimum performance.
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
A large ground pin copper area will help to lower the device temperature.
A multi-layer board with a separate ground plane is recommended.
Traces carrying large currents should be direct.
Trace area at pin FB should be as small as is practical.
The lead-length to the battery should be as short as is practical.
www.austriamicrosystems.com/DC-DC_Step-Up/AS1337
Revision 1.04
11 - 14
AMSCO [ AMS(艾迈斯) ]
