ZLED7015 Datasheet

© 2016 Integrated Device Technology, Inc.

14

April 20, 2016

(

)

S

FB

DC

FB

OUT

R

R

V

V

R

V

I













−

×

−

=

4

3

EN

LX

AGND

ZLED7015

LED

String

FB

PGND

OVP

VP

VDD

Microcontroller PMW Signal

5V

0V

The output current controlled by the DC voltage on FB can be calculated using equation (2):

(2)

Where

2.2.3

Dimming via PWM Control

An external pulse-width modulated (PWM) signal input can be used to control the LED output current by driving

the output current to a value below the nominal average value defined in section 2.2.1. A microcontroller can be

used to generate the PWM signal. See Figure 2.3 for an example circuit. The PWM signal is superimposed on the

ripple. This method of controlling dimming is similar to the external DC voltage control described in section 2.2.2.

The duty cycle of the PWM signal regulates the filtered DC voltage level, which inversely controls the LED output

current level. When the duty cycle is at 100%, the output current is at the minimum. With a 0% duty cycle, the

output current is at the maximum.

Ω and a PWM frequency of >2kHz to

minimize the filtered PWM voltage ripple.

dimming applications.

Figure 2.3

Example Circuit for Controlling Output Current via a PWM Control Signal