TLC5929 Datasheet, PDF (25/36 Pages) Texas Instruments – 16-Channel, Constant-Current LED Driver with 7-Bit Global Brightness Control, Power-Save Mode

TLC5929
www.ti.com
SBVS159 – APRIL 2011
LED SHORT DETECTION (LSD)
The LSD data are stored into a 16-bit register called SID holder at the rising edge of BLANK when the SIDLD
bits are set to '10' (see Table 6) or when IDM is enabled. The LSD bits are stored in the SID holder at the end of
the IDM working time (IDMTIM). The stored LSD data can be read out through the common shift register as SID
at the SOUT pin. Note that the LOD/LSD bits are not stable during the first 0.5 µs after the falling edge of
BLANK.
LSD data detect a fault caused by a shorted LED by comparing the OUTn voltage to the LSD detection threshold
voltage level set by LSDVLT in the control data latch (see Table 4 and Table 7). If the OUTn voltage is higher
than the programmed voltage, 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 enabled. LSD
data for outputs that are programmed to be disabled are always '0' (see Table 11), except when IDM is enabled.
When the device resumes operation from the power-save mode, LSD cannot be executed before the propagation
delay (t_D4) has elapsed because LSD does not work during power-save mode.
INVISIBLE DETECTION MODE (IDM)
Invisible detection mode (IDM) can detect LOD and LSD even when the output on/off data are set to the off
state. When the IDMCUR bits in the control data latch are set to any value except '00', all outputs start sinking
the current set by the IDMCUR bits at the falling edge of BLANK and stop sinking the current at the rising edge
of BLANK, or the time set by IDMTIM has elapsed. When OUTn stops, the selected SID data by SIDLD bits are
latched into the SID holder.
When the IDMCUR bits in the control data latch are set to '00', IDM is disabled.
Figure 26 shows the LOD/LSD/OLD/IDM circuits. Figure 27 and Figure 28 illustrate the IDM operation timing and
Table 12 shows a truth table for LOD/LSD/OLD.
VCC
VLED
OLD
Control
2 mA (typ)
LED Lamp
LSD/OLD Data
‘1’ = Error
LOD Data
‘1’ = Error
V_LSD
On/Off
Control
Up to
50 mA
IDM
Control
OUTn
2 mA/10 mA/20 mA
(typ)
V_LOD
GND
Figure 26. LOD/LSD/OLD/IDM Circuit
Table 12. LOD/LSD/OLD Truth Table
LOD
LED is not opened (V_OUTn >
V_LOD)
LED is open or shorted to GND
(V_OUTn ≤ V_LOD)
LSD
OLD
LED is not shorted (V_OUTn ≤
V_LSD)
OUTn does not leak to GND
(V_OUTn > V_LSD when
constant-current output off and
OUTn source current on)
LED is shorted between anode
and cathode, or shorted to higher
voltage side (V_OUTn > V_LSD)
Current leaks from OUTn to
internal GND, or OUTn is shorted
to external GND with high
impedance (V_OUTn ≤ V_LSD when
constant-current output off and
OUTn source current on)
CORRESPONDING BIT IN SID
0
1
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