TLC5929 Datasheet, PDF (15/36 Pages) Texas Instruments – 16-Channel, Constant-Current LED Driver with 7-Bit Global Brightness Control, Power-Save Mode

TLC5929
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DETAILED DESCRIPTION
SBVS159 – APRIL 2011
MAXIMUM CONSTANT SINK CURRENT
The maximum output current of each channel (I_OLCMax) is programmed by a single resistor (R_IREF) that is placed
between the IREF and GND pins. The current value can be calculated by Equation 1:
R=
IREF
V_IREF
I_OLCMax
´ 54.8
Where:
V_IREF = the internal reference voltage on IREF (typically 1.205 V when the global brightness control data are
at maximum.
I_OLCMax = 1 mA to 40 mA for V_CC ≤ 3.6 V, or 1 mA to 50 mA for V_CC > 3.6 V at OUT0 to OUT15 with BC =
7Fh
(1)
I_OLCMax is the highest current for each output. Each output sinks I_OLCMax 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. R_IREF must be between 1.32 kΩ and 66.0 kΩ in order to hold I_OLCMax between 50 mA
(typ) and 1 mA (typ). Otherwise, the output may be unstable. Output currents lower than 1 mA can be achieved
by setting I_OLCMax to 1 mA or higher and then using the global brightness control to lower the output current.
Figure 8 and Table 1 show the characteristics of the constant-current sink versus the external resistor, R_IREF.
Table 1. Maximum Constant Current Output versus
External Resistor Value
I_OLCMax (mA)
50 (V_CC > 3.6 V only)
45 (V_CC > 3.6 V only)
40
35
30
25
20
15
10
5
2
1
R_IREF (kΩ, typ)
1.32
1.47
1.65
1.89
2.20
2.64
3.30
4.40
6.60
13.2
33.0
66.0
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