TLC5971_15 Datasheet, PDF (18/45 Pages) Texas Instruments – 12-Channel, 16-Bit, Enhanced Spectrum, PWM, RGB, LED Driver

TLC5971
SBVS146D – AUGUST 2010 – REVISED DECEMBER 2015
www.ti.com
Feature Description (continued)
8.3.4 Thermal Shutdown
The thermal shutdown (TSD) function turns off all IC constant-current outputs when the junction temperature (T_J)
exceeds the threshold (T_TSD = 165°C, typical). When the junction temperature drops below (T_TSD – T_HYS), the
output control starts at the first GS clock in the next display period.
8.3.5 Noise Reduction
Large surge currents may flow through the IC and the board if all 12 outputs turn on simultaneously at the start of
each GS cycle. These large current surges could induce detrimental noise and EMI into other circuits. The
TLC5971 turns on the outputs for each color group independently with a 25 ns (typical) rise time. The output
current sinks are grouped into three groups. The first group that is turned on/off are OUTR0-3; the second group
that is turned on/off are OUTG0-3; and the third group is OUTB0-3. However, the state of each output is
controlled by the selected GS clock; see the Output Timing Select Function section.
8.4 Device Functional Modes
8.4.1 Maximum Constant Sink Current Setting
The maximum constant sink current value for each channel, I_OLCMax, is programmed through a single resistor,
R_IREF, placed between IREF and GND. The desired value can be calculated with Equation 6:
R_IREF (kW) =
V_IREF (V)
I_OLCMax (mA)
´ 41
where:
V_IREF = the internal reference voltage on the IREF pin (1.21 V, typically, when the the global brightness
control data are at maximum),
I_OLCMax = 2 mA to 60 mA.
(6)
I_OLCMax is the maximum current for each output. Each output sinks the I_OLCMax current when it is turned on and
global brightness control data (BC) are set to the maximum value of 7Fh (127d).
R_IREF must be between 0.82 kΩ and 24.8 kΩ to hold I_OLCMax between 60 mA (typical) and 2 mA (typical).
Otherwise, the output may be unstable. Output currents lower than 2 mA can be achieved by setting I_OLCMax to 2
mA or higher and then using global brightness control to lower the output current. The constant-current sink
values for specific external resistor values are shown in Figure 5 and Table 1.
Table 1. Maximum Constant-Current vs External Resistor Value
I_OLCMax (mA)
60
55
50
45
40
35
30
25
20
15
10
5
2
R_IREF (kΩ, Typical)
0.827
0.902
0.992
1.1
1.24
1.42
1.65
1.98
2.48
3.31
4.96
9.92
24.8
18
Submit Documentation Feedback
Product Folder Links: TLC5971
Copyright © 2010–2015, Texas Instruments Incorporated