TLC5971 Datasheet, PDF (16/37 Pages) Texas Instruments – 12-Channel 16-Bit, Enhanced Spectrum PWM, RGB LED Driver with 3.3-V Linear Regulator

TLC5971
SBVS146 – AUGUST 2010
APPLICATION INFORMATION
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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 1:
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.
(1)
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 11 and Table 1.
Table 1. Maximum Constant-Current versus 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
16
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