TLC5946_16 Datasheet, PDF (18/41 Pages) Texas Instruments – 16-Channel, 12-Bit PWM LED Driver with 6-Bit Dot Correction

TLC5946
SLVS824B – MARCH 2008 – REVISED JUNE 2008 .......................................................................................................................................................... www.ti.com
ERROR INFORMATION OUTPUT
The TLC5946 has two error detection circuits: LED open detection (LOD) and a thermal error flag (TEF). LOD
detects a broken or disconnected LED during the display period. The TEF indicates an over-temperature
condition. A low-level output of XERR indicates that an LOD error or TEF is detected. XERR pins of more than
two ICs can be connected together and pulled up to V_CC with a single resistor because XERR is an open-drain
output; see the SCLK and GSCLK Frequency section. Table 2 shows the XERR truth table. BLANK = H masks
LOD to distinguish between LOD and TEF. When the IC is powered on, XERR does not show correct values.
XERR shows a correct signal when LOD data become valid at the rising edge of the 33rd GSCLK pulse after
BLANK goes low. Also, both the LOD error and the TEF are shifted out of the SOUT pin; see the Status
Information Data (SID) section.
Table 2. XERR Truth Table
LOD (Internal)
0
0
1
1
0
0
1
1
ERROR DATA
CONDITION
TEF (Internal)
0
1
0
1
0
1
0
1
INPUT
BLANK
L
H
XERR
H
L
L
L
H
L
H
L
CONTINUOUS BASE LED OPEN DETECTION (LOD)
The LOD function automatically updates LOD data at the rising edge of the 33rd GSCLK pulse after BLANK goes
low; the LOD data are retained until the next 33rd GSCLK. LOD data are only checked for outputs that are
turned on during the rising edge of the 33rd GSCLK pulse. The internal LOD data becomes '1' when the voltage
of the OUTn pin is less than the LED open detection threshold (V_LOD = 0.3 V, typical).
To eliminate false detection of open LEDs, the LED driver design must ensure that the TLC5946 output voltage
is greater than V_LOD when the outputs are on. The GS data should be equal to or higher than 21h (33d) to detect
LED open in every PWM cycle.
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