DocID026965 Rev 2

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ALED6001

Device description

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Figure 8. External synchronization signal timing diagram

7.3

LED current regulation and brightness control

The brightness of the LEDs connected at the output of the ALED6001 can be controlled by

applying the desired PWM signal at the PWMI pin. The boost controller is turned on and off

according to the duty cycle of the PWMI control signal. When the PWMI is high (and the

soft-start has been completed), the output (LED) current is regulated by keeping constant

the voltage drop across the external sensing resistor connected between the VFBP and

VFBN pins.

A buffered replica of PWMI is available at the PWMO for driving a dimming N-channel

MOSFET when superior dimming performance is required. In some applications a high-side

dimming switch could be desirable (e.g.: protection against output short-circuit to ground or

LED strings using the chassis as return) and a P-channel MOSFET can be used as shown

in Figure 9. Some additional components may be needed to avoid excessive voltage

between the gate and the source of such MOSFET.