PAM2841

Document number: DSxxxxx Rev. 1 - 5

10 of 16

www.diodes.com

September 2013

© Diodes Incorporated

PAM2841

A Product Line of

Diodes Incorporated

Dimming Control

There are 4 different types of dimming control methods:

1). Using an External PWM Signal to EN Pin

With the PWM signal applied to the EN pin, the PAM2841 is alternately turned on or off by the PWM signal. The LEDs operate at either zero or

full current. The average LED current changes proportionally with the duty cycle of the PWM signal. A 0% duty cycle turns off the PAM2841 and

leads to zero LED current. A 100% duty cycle generates full current.Also the recommend dimming frequency is between 100Hz and 200Hz.

Figure. 1

2). Using an External PWM Signal to NMOS Gate.

When PWM signal is at high level, N MOSFET turned on, then pull comp pin down, then the LED current should be zero. When PWM signal is at

low level, N MOSFET turned off. The circuit uses resistor R1 to set the on state current. The average LED current changes proportionally with

the duty cycle of the PWM signal. A 100% duty cycle turns off the PAM2841 and leads to zero LED current. A 0% duty cycle generates full

current.

Also the recommend frequency is between 100 and 500Hz. Frequency<100Hz can naturally causes LEDs to blink visibly.

Figure. 2