TLC5951 Datasheet, PDF (35/46 Pages) Texas Instruments – 24-Channel, 12-Bit PWM LED Driver with 7-Bit Dot Correction and 3-Group, 8-Bit Global Brightness Control

TLC5951
www.ti.com
SBVS127B – MARCH 2009 – REVISED DECEMBER 2009
THERMAL SHUTDOWN AND THERMAL ERROR FLAG
The thermal shutdown (TSD) function turns off all constant-current outputs on the IC when the junction
temperature (T_J) exceeds the threshold (T_TEF = +163°C, typ) and sets the thermal error flag (TEF) to '1'. All
outputs are latched off when TEF is set to '1' and remain off until the next grayscale cycle after XBLNK goes high
and the junction temperature drops below (T_TEF – T_HYST). TEF remains as '1' until GSLAT is input with low
temperature. TEF is set to '0' once the junction temperature drops below (T_TEF – T_HYST), but the output does not
turn on until the first GSCKR/G/B in the next display period even if TEF is set to '0'.
GSLAT
GSCK
Grayscale
Data Latch
Old Latched GS Data
New Latched GS Data
XBLNK⁽¹⁾
GSCKR/G/B
1234
4094 4096
4093 4095
123
IC Junction
Temperature (T_J)
T_J < T_(TEF)
TEF in SID
(Internal Data)
'0'
OUTRn/Gn/Bn
OFF
ON
T_J ³ T_(TEF)
T_J < T_(TEF) - T_(HYS)
The TEF bit of SID is rest to ‘0’ at the rising edge of GSSCK
after the falling edge of GSLAT for a GS data write.
'1'
'0'
OUTRn/Gn/Bn is forced off when T_J exceeds T_(TEF).
Also, the TEF bit is set to ‘1’ at the same time.
OFF
ON
T_J ³ T_(TEF)
OUTRn/Gn/Bn is turned off at the rising edge of GSCKR/G/B
after the rising edge of XBLNK.
(1) The following internal signal also works to turn the constant outputs on as same as XBLNK inputting. The internal blank signal is
generated when GSLAT is input for GS data with display timing reset enabled. Also, the signal is generated at the 4096th GSCKR/G/B when
auto repeat mode is enabled. XBLNK can be connected to VCC when the display timing reset or auto repeat is enabled.
Figure 49. TEF/TSD Timing
NOISE REDUCTION
Large surge currents may flow through the IC and the board on which the device is mounted if all 24 outputs turn
on simultaneously at the start of each grayscale cycle. These large current surges could induce detrimental noise
and electromagnetic interference (EMI) into other circuits. The TLC5951 turns the outputs on in a series delay for
each group independently to provide a circuit soft-start feature. The output current sinks are grouped into four
groups in each color group. For example, for the RED color output, the first grouped outputs that are turned
on/off are OUTR0 and OUTR4. The second grouped outputs that are turned on/off are OUTR1 and OUTR5. The
third grouped outputs are OUTR2 and OUTR6 and the fourth grouped outputs are OUTR3 and OUTR7. Each
grouped output is turned on and off sequentially with a small delay between groups. However, each color output
on and off is controlled by the color grayscale clock.
Copyright © 2009, Texas Instruments Incorporated
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