Outputs latch-off, Other applications – Rainbow Electronics MAX16823 User Manual
Page 8
MAX16823
High-Voltage, 3-Channel Linear High-Brightness
LED Driver with Open LED Detection
8
_______________________________________________________________________________________
ICM7555. When V
STOP
is present, DIM is pulled up to
V
STOP
. The PWM dimming operation is disabled and
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
LEDGOOD connected through a resistor to V
REG
. This
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
operation, Q1 is off and R
CS1
sets the output current. In
STOP operation, Q1 turns on and the output current is
set by a parallel combination of R
CS1
and R2.
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.
V
V
V
V
V
IN MIN
BE MAX
FT MAX
CS
DO MAX
(
)
(
)
(
)
_
(
)
>
+
+
+
DIM
t
ON
LEDGOOD
LEDGOOD GOES
LOW WHEN t
OFF
> t
DELAY
t
OFF
Figure 1. LEDGOOD Timing Delay
IN
DIM2
CS1
REG
OUT1
GND
R
CS1
R
CS2
R
CS3
LEDs
0.1µF
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
100kΩ
Figure 2. PWM Dimming Operation with ICM7555