TLC5955 Datasheet, PDF (26/53 Pages) Texas Instruments – TLC5955 48-Channel, 16-Bit, PWM LED Driver with DC, BC, LED Open-Short Detection, and Internal Current Setting

TLC5955
SBVS237 – MARCH 2014
www.ti.com
8.3.4 LED Open Detection (LOD)
LOD detects a fault caused by an LED open circuit or a short from OUTXn to ground with low resistance by
comparing the OUTXn voltage to the LOD detection threshold voltage (0.3 V, typically). If the OUTXn voltage is
lower than the threshold voltage when OUTXn is on, that output LOD bit is set to 1 to indicate an open LED.
Otherwise, the LOD bit is set to 0. LOD data are only valid for outputs that are programmed to be on. LOD data
are latched into the LOD, LSD data latch at the 33rd GSCLK. LOD data for outputs programmed to be off at the
33rd GSCLK are always 0. The LED open detection circuit is shown in Figure 25 and Table 7 lists an LOD truth
table. Refer to Figure 26 for an LOD read timing diagram.
8.3.5 LED Short Detection (LSD)
LSD data detect a fault caused by a shorted LED between LED terminals by comparing the OUTXn voltage to
the LSD detection threshold voltage level set by LSDVLT in the control data latch. If the OUTXn voltage is higher
than the programmed voltage when OUTXn is on, the corresponding output LSD bit is set to 1 to indicate a
shorted LED. Otherwise, the LSD bit is set to 0. LSD data are only valid for outputs that are programmed to be
on. LSD data are latched into the LOD, LSD data latch at the 33rd GSCLK. LSD data for outputs programmed to
be off at the 33rd GSCLK are always 0. The LSD open detection circuit is shown in Figure 25 and Table 7 lists
an LSD truth table. Refer to Figure 26 for an LSD read timing diagram.
VLED
LED Lamp
LSD Data
1 = Error
LOD Data
1 = Error
V_LSD
PWM
Control
OUTXn
Constant current is set
by MC data.
V_LOD
GND
Figure 25. LOD and LSD Circuit
SID DATA
0
1
Table 7. LOD and LSD Truth Table
LOD
LED is not opened (V_OUTXn > V_LOD)
LED is open or shorted to GND (V_OUTXn ≤ V_LOD)
CONDITION
LSD
LED is not shorted (V_OUTXn ≤ V_LSD)
LED is shorted between anode and cathode, or shorted to
higher voltage side (V_OUTXn > V_LSD)
26
Submit Documentation Feedback
Product Folder Links: TLC5955
Copyright © 2014, Texas Instruments Incorporated