TLC5948A Datasheet, PDF (18/50 Pages) Texas Instruments – 16-Channel, 16-Bit, ES-PWM, Full Self-Diagnosis LED Driver

TLC5948A
SBVS192 – MARCH 2012
DETAILED DESCRIPTION
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MAXIMUM CONSTANT SINK CURRENT VALUE
The maximum output current value 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 = ^VIREF 42.3
´ _IREF
I_OLCMax
Where:
V_IREF = the internal reference voltage on IREF (typically 1.20 V when the global brightness control data are at
maximum)
I_OLCMax = 2 mA to 60 mA with DCn and BC = 7Fh
(1)
I_OLCMax is the highest current for each output. Each output sinks I_OLCMax current when it is turned on, and the dot
correction (DC) data and the global brightness control (BC) data are set to the maximum value of 7Fh (127).
Each output sink current can be reduced by lowering the DC and BC value.
R_IREF must be between 0.846 kΩ and 25.4 kΩ in order to hold I_OLCMax between 60 mA (typ) and 2 mA (typ).
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 DC or global BC to lower the output current.
Table 1 shows 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)
60 (V_CC > 3.6 V only)
55 (V_CC > 3.6 V only)
50 (V_CC > 3.6 V only)
45
40
35
30
25
20
15
10
5
2
R_IREF (kΩ, typ)
0.846
0.923
1.02
1.13
1.27
1.45
1.70
2.03
2.53
3.38
5.08
10.2
25.4
18
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