Datasheet

VIN
VOUT
VDx
Driver
current limit
Buck-boost
converter
GREENRED
R_EN
G_EN
B_EN
BLUE GREENRED GREENRED BLUE GREENRED
PWM
100% 80%
BRIGHTNESS
100% 0%
t > Timeout t < Timeout
100% 80% 100% MINIMUM
60 Hz
LM3549
SNVS640A –AUGUST 2010–REVISED MAY 2013 www.ti.com
Figure 18. PWM Timing
FAULT DETECTION
LM3549 can detect several different fault conditions. These are LED open, LED short, thermal shutdown (TSD),
under voltage lockout (UVLO) and buck-boost converter over current protection (OCP). If any of the fault
conditions occur corresponding fault bit is set in the fault register. If fault mask bit is not set also Fault output is
pulled low. Reading Fault register resets its value to zero and sets Fault output to high impedance state.
LED OPEN FAULT
Open fault is generated when at the end of color VOUT is at maximum and no current is flowing through driver
(VDx = 0V). Also OCP fault needs to be low. Open fault can be generated by broken LED or a soldering defect.
Figure 19. LED Open Fault
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