AS1336 austriamicrosystems, AS1336 Datasheet - Page 14

• Manufacturer Part Number: AS1336
• Description: Dual, Low Voltage, Micropower Dc-dc Step-up Converters
• Manufacturer: austriamicrosystems

AS1336
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
External Component Selection
Inductor Selection
The fast switching frequency (1.2MHz) of the AS1336 allows for the use of small surface mount or chip inductor for the
external inductor
3.3µH is the required minimum value for the external inductor. Larger inductor values allow greater output current
capability by reducing the inductor ripple current. Increasing the inductance above 10µH will increase size while provid-
ing negligible improvement in output current capability.
The approximate output current capability of the AS1336 versus inductor value is given in:
Where:
η is the estimated efficiency;
I
V
D is the steady-state duty ratio = (V
f is the switching frequency (1.2MHz typ);
L is the inductor value.
The inductor current ripple is typically set for 20 to 40% of the maximum inductor current (I
core inductor materials reduce frequency dependent power losses compared to less expensive powdered iron types,
which result in improved converter efficiency.
The inductor should have low ESR to reduce the I²R power losses, and must be able to handle the peak inductor cur-
rent without saturating. Molded chokes and some chip inductors normally do not have enough core to support the peak
inductor currents of the AS1336 (850mA typ). To minimize radiated noise, use a toroid, pot core, or shielded bobbin
inductor.
Table 4. Recommended External Components
www.austriamicrosystems.com/DC-DC_Step-Up/AS1336
P
IN
is the peak current limit value (0.6A);
is the input voltage;
Name
L1
(see Figure 26 on page
LQH32PN4R7NN0
LQH32PN6R8NN0
LQH32PN100MN0
EPL2010-472ML
EPL2010-682ML
EPL2010-103ML
Part Number
OUT
I
- V
OUT MAX
10).
IN
(
)/V
4.7µH
6.8µH
4.7µH
6.8µH
Value
10µH
10µH
OUT
)
=
;
η
Revision 1.01
⋅
Rating
0.85A
0.65A
0.57A
0.47A
⎛
⎝
0.7A
I
1A
P
–
V
----------------- -
f L 2
⋅
IN
⋅
⋅
216m Ω
288m Ω
456m Ω
429m Ω
512m Ω
914m Ω
D
Type
⎞
⎠
⋅
(
1 D
–
3.2x2.5x1.55mm Murata
3.2x2.5x1.55mm
3.2x2.5x1.55mm
2.0x2.0x1.0mm Coilcraft
2.0x2.0x1.0mm
2.0x2.0x1.0mm
)
Size
P
). High-frequency ferrite
www.murata.com
www.coilcraft.com
Manufacturer
(EQ 3)
14 - 18