AS1343 datasheet(11/17 Pages) AMSCO

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AS1343

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

LED Power Supply Application

The AS1343 can also be used for driving LEDs. Just simply connect the LEDs between the pins VOUT and FB. (see

Figure 29).

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 (VF) of the used LEDs and the Feeback Voltage VFB.

Calculate VOUT by:

Note:

The brightness of the LEDs can directly be adjusted by setting the current ILED via the corresponding R2.

Calculate R2 by:

Where:

VFB = 1.25V

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 (TJ) reaches 140ºC (typ). When TJ decreases to

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 TJ within the range between 135 and 140ºC.

3, 8

GND

VCC

Off

AS1343

6.8µH

10µF

VCC = 0.9V

to 3.6V

COUT

4.7µF

100

SWOUT

PGND

VOUT

POK

100k

ILED

(EQ 4)

VOUT

VF ILED

() n

VFB

(EQ 5)

ILED

VFB

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