BCR420UW6 Datasheet, PDF (11/13 Pages) Diodes Incorporated – LINEAR LED CONSTANT CURRENT REGULATOR IN SOT26

Application Information (Cont.)
REXT
(Optional)
Figure 5 Application Circuit for LED Driver
with Reverse Polarity Protection
BCR420UW6 / BCR421UW6
To remove the potential of incorrect connection of the power supply
damaging the lamp’s LEDs, many systems use some form of
reverse polarity protection.
One solution for reverse input polarity protection is to simply use a
diode with a low VF in line with the driver/LED combination. The low
VF increases the available voltage to the LED stack and dissipates
less power. A circuit example is presented in Figure 5 which
protects the light engine although it will not function until the problem
is diagnosed and corrected. An SDM10U45LP (0.1A/45V) is shown,
providing exceptionally low VF for its package size of 1mm x 0.6mm.
Other reverse voltage ratings are available from Diodes
Incorporated’s website such as the SBR02U100LP (0.2A/100V) or
SBR0220LP (0.2A/20V).
While automotive applications commonly use this method for
reverse battery protection, an alternative approach shown in Figure
6, provides reverse polarity protection and corrects the reversed
polarity, allowing the light engine to function.
The BAS40BRW incorporates four low VF Schottky diodes in a
single package, reducing the power dissipated and maximizes the
voltage across the LED stack.
Figure 7 shows an example configuration for 350mA operation. In
such higher current configurations adequate enable current is
provided by increasing the enable voltage.
REXT
(Optional)
Figure 6 Application Circuit for LED Driver with
Assured Operation Regardless Of Polarity
REXT =
2.1
Figure 7 Example for 350mA Operation
BCR420UW6 / BCR421UW6
Document number: DS37667 Rev. 4 - 2
11 of 13
www.diodes.com
June 2016
© Diodes Incorporated