TLC5928_16 Datasheet, PDF (17/32 Pages) Texas Instruments – 16-Channel, Constant-Current LED Driver with LED Open Detection

TLC5928
www.ti.com
SBVS120E – JULY 2008 – REVISED JANUARY 2011
STATUS INFORMATION DATA (SID)
The latched LED open detection (LOD) error and pre-thermal warning (PTW) in the SID data latch are shifted out
onto the SOUT pin with each rising edge of SCLK. If a PTW is reported, all LOD error bits are set to '1'. The SID
data are written over the data in the on/off control shift register at the rising edge of LAT. Therefore, the previous
data in the on/off control shift register are lost when SID information is latched in. Figure 20 shows the SID bit
assignments. See Figure 7 for the read timing of SID.
When the IC is powered on, the initial LOD data are invalid. Therefore, LOD data must be read after the rising
edge of BLANK. Table 3 shows a truth table for LOD and PTW.
LED open detection (LODn)
Pre-thermal warning (PTW)
Table 3. LOD and PTW Truth Table
CONDITION
LED is connected (V_OUTn > V_LOD)
LED is opened or shorted to GND
(V_OUTn ≤ V_LOD and output on)
IC temperature is low (IC temperature ≤ T_(PTW))
IC temperature is high (IC temperature > T_(PTW))
SID DATA
'0' (low level at SOUT)
'1' (high level at SOUT); set to the bit that has an
LED error condition
Depend LED open error
All bits = '1' (high level at SOUT)
SID Data Latch (1 Bit ´ 16 Channels)
MSB
15
14
13
12
11
OUT15
LOD Data
(LOD 15)
OUT15
LOD Data
(LOD 14)
OUT15
LOD Data
(LOD 13)
OUT15
LOD Data
(LOD 12)
¼
4
3
2
OUT15
LOD Data
(LOD 3)
OUT15
LOD Data
(LOD 2)
All Bits Become ‘1’ When the IC is in a PTW (Pre-Thermal Warning) Condition
1
OUT15
LOD Data
(LOD 1)
LSB
0
OUT15
LOD Data
(LOD 0)
¼
SOUT
MSB
15
14
13
12
11
On/Off Data
for
OUT15
On/Off Data
for
OUT14
On/Off Data
for
OUT13
On/Off Data
for
OUT12
¼
LSB
4
3
2
1
0
On/Off Data On/Off Data
for
for
OUT3
OUT2
On/Off Data On/Off Data
for
for
OUT1
OUT0
The 16 bits in the SID latch are loaded into the on/off shift register at the rising edge of LAT.
SID Control Shift Register (1 Bit ´ 16 Channels)
Figure 20. Status Information Data Configuration
SIN
SCLK
LAYOUT CONSIDERATIONS
The output current transient time in the TLC5928 is very fast. In addition, all outputs turn on or off at the same
time to minimize the output on-time error. This high current demand can cause GND to shift in the entire system,
and lead to false triggering of signals. To overcome this issue, design all GND lines to be as wide and short as
possible in order to reduce parasitic inductance and resistance.
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