AS1343 austriamicrosystems AG, AS1343 Datasheet - Page 11

• Manufacturer Part Number: AS1343
• Description: DC-DC Boost Converter
• Manufacturer: austriamicrosystems AG

LED Power Supply Application
The AS1343 can also be used for driving LEDs. Just simply connect the LEDs between the pins V
Figure
Figure 29. LED Supply Application
The output voltage is adjusted automatically to the required voltage of the LEDs. This voltage depends on the forward
voltage (V
Calculate V
Note: The brightness of the LEDs can directly be adjusted by setting the current I
Calculate R
Where:
V
n .... number of LEDs
Thermal Protection
To protect the device from short circuit or excessive power dissipation of the auxiliary NPNs, the integrated thermal
protection switches off the device when the junction temperature (T
approximately 135ºC, the device will resume normal operation. If the thermal overload condition is not corrected, the
device will switch on and off while maintaining T
AS1343
Datasheet - A p p l i c a t i o n I n f o r m a t i o n
www.austriamicrosystems.com
FB
= 1.25V
29).
V
CC
to 3.6V
F
= 0.9V
) of the used LEDs and the Feeback Voltage V
OUT
2
by:
10µF
On
Off
by:
C
1
100kΩ
R
3
PGND
POK
V
EN
CC
2
4
1
5
V
OUT
J
within the range between 135 and 140ºC.
AS1343
=
7
SWOUT
I
Revision 1.04
LED
V
F
(
I
FB
LED
=
6.8µH
.
V
--------- -
L
R
1
) n
FB
2
×
+
J
) reaches 140ºC (typ). When T
V
FB
6
LX
9
VOUT
10
FB
3, 8
GND
100Ω
D1
R
LED
2
via the corresponding R
I
LED
4.7µF
C
OUT
OUT
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J
decreases to
and FB.
(EQ 4)
(EQ 5)
2
(see
11 - 17
.