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| TLC59291_16 Datasheet, PDF (25/46 Pages) Texas Instruments – 8/16-Channel, Constant Current LED Driver | |||
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TLC59291
SLVSA96A â SEPTEMBER 2015 â REVISED MARCH 2016
8.3 Feature Description
8.3.1 Maximum Constant Sink Current
The maximum output current of each channel (IO(LCmax)) is programmed by a single resistor (RIREF) that is placed
between the IREF and GND pins. The current value can be calculated by Equation 1:
RIREF(KW)
=
VIREF(V)
IO(CL max)(mA)
x
54.8
Where:
VIREF = the internal reference voltage on IREF (typically 1.205 V when the global brightness control
data are at maximum.
IO(LCmax) = 1 mA to 40 mA ( VCC ⤠3.6 V), or 1 mA to 50 mA (VCC > 3.6 V) at OUT0 to OUT15 (BC =
7Fh)
(1)
IO(LCmax) is the highest current for each output. Each output sinks IO(LCmax) current when it is turned on with the
maximum global brightness control (BC) data. Each output sink current can be reduced by lowering the global
brightness control value. RIREF must be between 1.32 kΩ and 66 kΩ to hold IO(LCmax) between 50 mA (typical) and
1 mA (typical). Otherwise, the output may be unstable. Output currents lower than 1 mA can be achieved by
setting IO(LCmax) to 1 mA or higher and then using the global brightness control to lower the output current.
Figure 14 and Table 1 show the characteristics of the constant-current sink versus the external resistor, RIREF.
Table 1. Maximum Constant Current Output versus
External Resistor Value
IO(LCmax) (mA)
50 (VCC > 3.6 V only)
45 (VCC > 3.6 V only)
40
35
30
25
20
15
10
5
2
1
RIREF (kΩ, typ)
1.32
1.47
1.65
1.89
2.20
2.64
3.30
4.40
6.60
13.2
33
66
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