5

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

48102.002

LED Drivers

LC5200 Series

Application Information

Typical Application Example

A typical application circuit is shown in figure 1. The values of

the external components are shown in the adjacent table.

Component Value Setting

LED

LED current should not exceed the LC5200 device current

ratings. Set the total voltage drop across the LED string to be

design rule, the PWM off-time should be longer if there is a small

drop in voltage across the LED string, and it should be shorter

if there is a high drop in voltage across the LED string. For the

LC5205D, a 9 to 30 V drop across the LED string is recom-

mended for proper operation.

LC5200

VBB

OUT

Sen

GND

Reg

Toff

Ref

LED

Di

L

Line

Filter

Input

Referenced Typical Application Components

Symbol

Components

Values / Ratings

Descriptions

Electrolytic capacitor

≈100 μF / 450 V

Main supply source voltage rectifying capacitor

Note: ≤ 1 μF can be used

Capacitor

0.1 μF / 25 V

The internal regulator output capacitor

Capacitor

100 pF / 25 V

PWM off-time adjusting capacitor

Di

Diode

RL3A

High voltage, ultrafast rectifying, current recirculation diode

L

Coil

1 mH / 1 A

PWMing choke coil

LED

LEDs

―――

LED load

Resistor

Reference pin voltage setup resistor

Resistor

Reference pin voltage setup resistor

Resistor

PWM off-time adjusting resistor

Resistor

1.0 Ω / 1 W

Output current sensing resistor

Figure 1. Typical application circuit