STLD20CP1

Application information

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6

Application information

6.1

Step-up

The STLD20CP1 is a PWM controller working at a 1.3 MHz frequency, designed to function

in discontinuous mode. The LED current regulation for the backlighting is achieved by

6.2

Shutdown and brightness control

The shutdown and brightness control functions are achieved by using the digital control pins

DM1 and DM2.

There are also other modes that can be used to perform dimming control on white LEDs.

The first is to use the truth table selection mode step-up that shows the behavior using a

preselected digital dimming control.

The second is a PWM dimming control mode, which is implemented by keeping a DMx pin

at a low or high value and the other DMx forcing a PWM digital signal up to 50 kHz with a

minimum duty cycle 5%. A 5% duty cycle corresponds to the minimum current and a 100%

duty cycle corresponds to full current. In cases where DM2 is a high value and DM1 is

forced with a PWM digital (Figure 4), the dimming control varies from 5% to 100% of current.

If DM2 is held low and the PWM signal is applied on DM1 (Figure 5), the dimming control

varies from 0 up to 60% of current.

Figure 4.

PWM dimming method from 5% to 100%