AS1320_1 AMSCO [austriamicrosystems AG], AS1320_1 Datasheet - Page 9

• Manufacturer Part Number: AS1320_1
• Description: 200mA Step-Up DC-DC Converter
• Manufacturer: AMSCO [austriamicrosystems AG]

AS1320
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
9 Application Information
Inductor Selection
The control circuitry of the AS1320 permits a wide range of inductor values to be selected – from 4.7 to 47µH; 10µH is
ideal for most applications.
The intended application should dictate the value of L. The trade-off between required PCB surface area and desired
output ripple are the determining factors: smaller values for L require less PCB space, larger values of L reduce output
ripple. If the value of L is large enough to prevent I
power will be reduced.
For maximum output current calculate the value for L as:
Where:
R
R
Note: Coils should be able to handle 500mA
Capacitor Selection
C
Choose a C
The value for C
Where:
r is the desired output ripple in %.
C
C
used to further reduce ripple and improve AS1320 efficiency.
PC Board Layout and Grounding
Well-designed printed circuit-board layout is important for minimizing ground bounce and noise.
www.austriamicrosystems.com
!
!
!
IND
NCH
IN
OUT
IN
reduces the peak current drawn from the battery and can be the same value as C
Place pin GND lead and the ground leads of C
Keep the lead to pin LX as short as possible.
To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the
Selection
GND pin directly to the ground plane.
is the inductor series resistance.
is the R
Selection
OUT
DS(ON)
OUT
value to achieve the desired output ripple percentage. A 22µF ceramic capacitor is a good initial value.
can be determined by:
of the N-channel MOSFET (0.3Ω typ).
I
OUT(MAX)
(V
BATT(MAX)
= [(0.7A/2)(V
C
OUT
(1µs))/0.7A < L < (V
> (L + 2.5µH) x V
RMS
BATT(MIN)
MAX
and have a I
IN
Revision 1.03
and C
from being reached before t
- (0.7A/2)(R
OUT
BATT(MAX)
BATT(MIN)
SAT
as close to the device as possible.
≥ 1A and should have a R
NCH
2
(7µs))/0.7A
/ r%
+ R
IND
))]/V
ON
OUT
OUT
expires, the AS1320 output
. A larger value for C
IND
≤ 100mΩ.
IN
can be
(EQ 2)
(EQ 3)
(EQ 4)
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