ACT6311 datasheet(5/10 Pages) ACTIVE-SEMI

5 / 10 page

ACT6311

Innovative PowerTM

- 5 -

www.active-semi.com

Rev 3, 22-Feb-11

PART NUMBER

CURRENT

RATING

(MA)

DCR

(Ω)

SUPPLIER

CDRH3D16-220

350

0.5

Sumida

ELJPC220KF

160

4.0

Panasonic

LQH3C220

250

0.7

Murata

LEM2520-220

125

5.5

Taiyo Yuden

PART

NUMBER

IF(MA)

VRRM (V)

SUPPLIER

CMDSH-3

100

Central

CMDSH2-3

200

Central

BAT54

200

Zetex

ILED (MA)

R1 (Ω)

246

124

103.3

82.7

APPLICATION INFORMATION

Inductor Selection

Table 1:

Recommended Inductors

A 22µH inductor is typically used for the ACT6311.

The inductor should have low DC resistance (DCR)

and losses at 1MHz. See Table 1 for examples of

small size inductors.

Capacitor Selection

The ACT6311 only requires a 1µF input capcitor

and a 1µF output capacitor for most applications.

Ceramic capacitors are ideal for these applications.

For best performance, use X5R and X7R type

ceramic capacitors, which possess less degradation

in capacitance over voltage and temperature

ranges.

Diode Selection

The ACT6311 requires a fast recovery Schottky

diode as the rectifier. Select a low forward voltage

drop Schottky diode with a forward current (IF)

rating of 100mA to 200mA and a sufficient peak

repetitive reverse voltage (VRRM). Some suitable

Schottkky diodes are listed in Table 2.

Table 2:

Recommended Schottky Diodes

OLED Application

Figure 1 shows the feedback network necessary to

set the output voltage. Select the proper ratio of the

two feedback resistors R1 and R2 based on the

desired output voltage. Typically choose R1 = 20kΩ

and determine R2 from the output voltage:

White LED Application

The LED current is determined by the value of the

feedback resistor R1. Because the FB input of the

IC is regulated to 1.24V, the LED current is

determined by ILED = 1.24V/R1. The value of R1 for

different LED currents is shown in Table 3.

Table 3:

R1 Resistor Value Selection

To improve efficiency, resistors R2 and R3 can be

connected as shown in Figure 4 to lower the

effective feedback voltage.

The following are dimming control methods for the

ACT6311 series white LED application.

1) PWM Signal Driving SHDN

When a PWM signal is connected to the SHDN pin,

the ACT6311 is turned on and off alternately under

the control of the PWM signal. The current through

the LEDs is either zero or full scale. By changing

the duty cycle of the PWM signal (typically 1kHz to

10kHz), a controlled average current is obtained.

2) DC Voltage Control

Figure 5 shows an application in which a DC

voltage is used to adjust the LED current. The LED

current increases when VDC is lower than VFB and

decreases when VDC is higher than VFB. In Figure 5,

the LED current range of 15mA to 0mA is controlled

by VDC = 0V to 2V.

3) Filtered PWM Control

Figure 6 shows an application using a filtered PWM

signal to control dimming.

4) Logic Control

A logic signal can be used to adjust the LED current

in a discrete step, as shown in Figure 7.

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