PAM2801SWAF095 datasheet(7/9 Pages) PAM

7 / 9 page

Dimming Control Using a PWM Signal to FB

Dimming Control Using a PWM Signal to

SHDN Pin

By using the PWM signal to FB pin as shown in

the Figure 2, the LED turns on or off and its

current operates at either 0mA or the set

maximum current. The PWM signal can be

considered as an adjustable DC voltage. As the

PWM duty cycle increases, the LED current

decreases. Typically, the PWM frequency ranges

from 5KHz to 40KHz.

Figure 2. Dimming Control Using a PWM Signal

to FB Pin

With the PWM signal applied to the SHDN pin of

the PAM2801, the LED turns on or off. When the

SHDN pin is high, the LED turn on and its current

is at the set maximum current; when the SHDN

pin is low, the LED turn off and its current turns to

0mA. The a verage LED c urrent increase

proportionally with the PWM duty cycle. A 0%

duty cycle produces 0mA of LED current; a 100%

duty cycle corresponds to the set maximum

current. The magnitude of the PWM signal

should be higher than the SHDN input high (V ).

The typical frequency of the PWM signal ranges

from 100Hz to 1KHz. Figure 3 shows the LED

current with the PWM duty cycle set to 50% and

the PWM frequency set respectively to 100Hz

and 1KHz. Figure 4 shows the LED current

versus the PWM duty cycle, setting the PWM

frequency to 100Hz.

100Hz

1 KHz

Figure 3. Dimming Control Using a PWM Signal

to SHDN Pin

Figure 4. LED Current vs Duty Cycle

（）

SHDN

LED

LED Current vs Duty Cycle

100

150

200

250

300

350

400

20406080

100

Duty Cycle(%)

08/2007

PAM2801

0.27

WLED

PWM

10KΩ

22kΩ

1KΩ

0.1uF

Application Information(continued)

SHDN

LED

PAM2801

1W High Power White LED Driver

Power Analog Microelectronics Inc

PAM2801SWAF095 数据表(PDF) 7 Page - Power Analog Micoelectronics

PAM2801SWAF095 数据表(HTML) 7 Page - Power Analog Micoelectronics

Html Pages

1 2 3 4 5 6 7 8 9

数据表下载