Application Note AN2xx56

BCR205W LED driver

INTERNAL ONLY

Application Note AN2xx213, 0.1

6 April 2011

4 / 11

1

Introduction

1.1

Features

 Wide input voltage range 1.8V – 18V

 Ultra low voltage overhead of only 0.2V

 5mA - 80mA LED drive current with external

transistor



 Tailored to drive LED up to 200 mW 

 Typical 3% LED current accuracy 

 No EMI 

 RoHS compliant (pb-free) 

 small SOT343 package 

Figure 1 BCR205W

1.2

Applications

 Channel letters

 Decorative lighting 

 Architectural lighting

 Gambling & vending machines lighting

 Refrigerator/freezer lighting for appliances and retail use  



1.3

Description

The BCR205W is a simple and low cost LED controller with an Ultra Low voltage

overhead providing to possibility to use the maximum amount of LEDs in series despite

following constraints

- LED forward voltage variation

- Voltage drop along long LED chains

- Tolerances in power supplies

- Varying battery voltage

The LED current is adjustable from 5mA to 80mA with a sense resistor. By using a digital

transistor as the power stage the number of external parts can be reduced to a minimum.

The small SOT-343 package allows the whole circuit to be realized on a very small PCB area.

1.4

Check List before powering up

Before powering on the BCR205 demo board, please verify the following:

 Make sure that the input voltage supply is less than 18V.

 Polarity of power supply must be correct.

 LED anode must connect to LED+, LED cathode must connect to LED-

 Be sure R7 and R9 is only one of them is on board.

 Please avoid reconnecting the LED array between LED+ and LED- terminals without powering down first.