Introduction

STLA02

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Doc ID 010005 Rev 1

7

Introduction

The STLA02 is a boost converter dedicated to powering and controlling the current of white

LEDs in an LCD backlight. The device operates at a typical constant switching frequency of

2.3 MHz. It steps an input voltage ranging from 2.5 V to 18 V, up to 27 V. The output current

device contains high side sensing to simplify the PCB layout in terms of connection of the

LEDs.

The output current is dimmable by the PWM signal applied to the EN pin with minimum

PWM frequency equal 100 Hz.

7.1

PWM input (EN)

Light intensity can be dimmed by a signal applied to the PWM (EN) input.

The PWM signal is directly connected to the enable pin of the STLA02. It is recommended

to use the frequency of the PWM signal in the range of 100 Hz to 1 kHz and amplitude of the

1.8 V) is shown in Figure 17.

Note:

When the device is required to operate in a constant current mode with the EN pin

of the device and the EN voltage is mandatory to guarantee the proper internal reset of the

7.2

Selection of the external components

It is recommended to use 1 µF as the input capacitor to achieve good stability of the device

It is recommended to use 1 µF as the optimal value of output capacitor to get the best

compromise between output voltage ripple and load transients response. The output ripple

can be checked according to the equation for step-up architecture:

Equation 1

Inductor selection

A thin shielded inductor with a low DC series winding resistance is recommended for this

application. To achieve a good efficiency in step-up mode, it is recommended to use an

resistance of the LED [

Ω; Ω; 1].

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