High-Voltage, 3-Channel Linear High-Brightness

LED Driver with Open LED Detection

8

_______________________________________________________________________________________

the LEDs light up to full brightness. See the ICM7555

data sheet for formulas to calculate the dimming fre-

quency and the duty cycle.

Outputs Latch-Off

Figure 3 shows a circuit with DIM1, DIM2, DIM3, and

circuit is useful for applications that require all outputs

to latch off when one of the LEDs opens. The

MAX16823 resumes current regulation again through

power cycling, once the fault condition is removed.

Other Applications

The application circuit in Figure 4 implements a two-

level brightness current for TAIL/STOP lights. In TAIL

STOP operation, Q1 turns on and the output current is

Figure 5 shows an application circuit with the

MAX16823 using a single BJT to provide high output

current. For proper operation:

For minimized dropout, the LEDs can be placed in the

collector.

VV

V

V

V

IN MIN

BE MAX

FT MAX

CS

DO MAX

(

)

()

()

_

(

)

>+

+

+

DIM

LEDGOOD

LEDGOOD GOES

Figure 1. LEDGOOD Timing Delay

IN

DIM2

CS1

REG

OUT1

GND

LEDs

0.1

μF

TH

TRG

GND

OUT

IN

DIS

ICM7555

R3

C2

R2

R1

D1

D4

C1

D2

D3

TAIL

STOP

DIM1

DIM3

OUT2

OUT3

CS2

CS3

MAX16823

100k

Ω

Figure 2. PWM Dimming Operation with ICM7555