TLC5943_17 Datasheet, PDF (16/40 Pages) Texas Instruments – 16-Channel, 16-Bit PWM LED Driver with 7-Bit Global Brightness Control

TLC5943
SBVS101 – DECEMBER 2007
www.ti.com
Brightness Control (BC) Function
The TLC5943 is able to adjust the output current of all channels (OUT0 to OUT15). This function is called
brightness control (BC). The BC function allows users to adjust the global brightness of LEDs connected to the
outputs OUT0 to OUT15. All channel output currents can be adjusted in 128 steps from 0% to 100% of the
maximum output current, I_OLCMax. The brightness control data are entered into the TLC5943 via the serial
interface.
Equation 2 determines the sink current for each output (OUTn):
I_OUTn
(mA)
=
I_OLCMax
(mA)
´
(
BCn
127d
)
(2)
Where:
• I_OLCMax = the maximum channel current for each channel determined by R_IREF
• BCn = the programmed brightness control value for OUTn (BCn = 0 to 127d)
When the IC is powered on, the data in the Brightness Control Shift Register and data latch 1 and 2 are not set
to any default values. Therefore, BC data must be written to the BC latch 1 and 2 before turning on the constant
current output.
Table 2 summarizes the BC data versus current ratio and set current value.
BC DATA
(Binary)
000 0000
000 0001
000 0010
... ...
111 1101
111 1110
111 1111
Table 2. BC Data versus Current Ratio and Set Current Value
BC DATA
(Decimal)
0
1
2
... ...
125
126
127
BC DATA
(Hex)
00
01
02
... ...
7D
7E
7F
SET CURRENT
RATIO TO
MAX CURRENT (%)
0.0
0.8
1.6
... ...
98.4
99.2
100.0
OUTPUT CURRENT
(mA, Typical)
AT I_OLCMax = 50 mA
0.0
0.4
0.8
... ...
49.2
49.6
50.0
OUTPUT CURRENT
(mA, Typical)
AT I_OLCMax = 5 mA
0.00
0.04
0.08
... ...
4.92
4.96
5.00
16
Submit Documentation Feedback
Product Folder Link(s): TLC5943
Copyright © 2007, Texas Instruments Incorporated