APW7000 查看數據表（PDF） - Anpec Electronics

零件编号

产品描述 (功能)

比赛名单

APW7000

1X/1.5X/2x Charge Pump White LED Driver

Anpec Electronics 

APW7000

Application Information (Cont.)

Brightness Control (Cont.)

3. Digital dimming with external NMOS transistors

The third method for dimming the LEDs is to change the

equivalent resistance for RSET with the external NMOS

transistors. The equivalent resistance is the parallel

combinations of the R1, R2, R3, and R4. R4 is always

connected and selected for the minimum LED current.

Figure 5 shows the application circuit.

Layout Consideration

The APW7000 is a high frequency charge pump for white

LED driver and requires some care when laying out the

printed circuit board. The metal GND pad of the bottom of

the package must be soldered to the PCB and connected

to the GND plane on the backside through several ther-

mal vias. Place the CIN, COUT, C1, and C2 as close to IC

as possible for reducing the switching noise.

APW7000

ISET

5

R1

R2

R3

R4

Figure 5. Digital Dimming Application Circuit

4. PWM dimming with EN pin

Another method for dimming the LEDs is to apply a PWM

signal into the EN pin. The average LED current is pro-

portional to the PWM signal duty cycle. Note that the fre-

quency of PWM signal will affect the minimum dimming

duty. The recommend dimming frequency is between

100Hz and 1kHz. The average LED current is calculated

by the following equation:

ILED(avg)

=

ton × ILED(max)

ton + toff

Where:

I

is programmed LED current by ISET pin

LED(max)

toff is the off time of the PWM signal

ton is the on time of the PWM signal

Copyright © ANPEC Electronics Corp.

13

Rev. A.2 - Feb., 2009

www.anpec.com.tw

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