as1323 austriamicrosystems, as1323 Datasheet - Page 8

• Manufacturer Part Number: as1323
• Description: 1.6?a Ultra-low Quiescent Current, Single Cell, Step-up Converter With Shutdown Output Disconnect - Tsot23-5
• Manufacturer: austriamicrosystems

AS1323
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
Figure 12. Typical Application
Inductor Selection
The control scheme of the AS1323 allows for a wide range if inductor values. A 10µH inductor should be sufficient for
most applications
Smaller inductance values typically offer smaller physical size for a given series resistance, allowing the smallest over-
all circuit dimensions. Applications using larger inductance values may startup at lower battery voltages, provide higher
efficiency and exhibit less ripple, but they may reduce the maximum output current. This occurs when the inductance is
sufficiently large to prevent the maximum current limit (I
expires
For maximum output current, the inductor value should be chosen such that the controller reaches the current-limit
before the maximum on-time is triggered:
t
I
For larger inductor values, the peak inductor current (I
The inductor’s incremental saturation current rating should be greater than the peak switching current. However, it is
generally advisable to bias the inductor into saturation by as much as 20%, although this will slightly reduce efficiency.
Maximum Output Current
The maximum output current (I
the formula for determining I
www.austriamicrosystems.com
ONMAX
LIMIT
is 400mA (typ).
is 6µs (typ).
(see Electrical Characteristics on page
(see Figure
OUTMAX
12).
OUTMAX
:
) is a function of I
10µF
I
OUTMAX
SHDNN
V
BATT
I
PEAK
4).
1
3
=
L
>
1
-- - I
2
AS1323
Revision 1.02
V
------------------------------- -
⋅
=
PEAK
BATT
PEAK
LIMIT
10µH
V
------------------------------- -
PEAK
I
LIMIT
BATT
) can be determined by:
) from being reached before the maximum on-time (t
⋅
, V
⋅
L
t
⎛
⎝
ON
V
---------------- -
⋅
IN
V
t
BATT
, V
ON
OUT
5
LX
2
V
4
V
OUT
SS
OUT
⎞ η
⎠
⋅
, and the overall efficiency (η) as indicated in
10µF
(EQ 3)
(EQ 1)
(EQ 2)
ON
8 - 13
)