點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC.

-8 -

Version

：A.001

PC112/PC113

General Description

Bias current setting

The PC112/PC113 is a DC/DC converter which provides a regulated current output

from a VDD input of DC 2.8V to 5.0V. Regulating the LED current can be achieved by

setting the resistor of FB pin to ground. So the value of the current setting resistor R2

could be set by:

R2=

LED

I

095

.

0

(Ω)

Brightness control

The brightness control can be achieved by applying a PWM control signal to EN

pin or by varying the current setting resistor R2, shown as follows.

PC113

PWM

EN

5

PC113

PWM

FB

4

R

MIN

R

INCR

PC113

V

ADJ

FB

4

R

A

R

2

R

B

To

LEDs

Fig. 3

Fig. 4

Fig. 5

We could apply a digital PWM signal (100Hz~3KHz) to EN pin (Fig. 3) to generate

a LED current waveform identical to that of the PWM signal waveform. The average

output LED current is calculated:

2

095

.

0

R

x Duty of PWM

(A)

Another control method is to vary the value of the current setting resistor (Fig. 4).

2

095

.

0

R

which R2 =

INCR

MIN

INCR

MIN

R

R

R

R

+

×

, PWM is High

(A)