TLC5948A Datasheet, PDF (19/50 Pages) Texas Instruments – 16-Channel, 16-Bit, ES-PWM, Full Self-Diagnosis LED Driver

TLC5948A
www.ti.com
SBVS192 – MARCH 2012
DOT CORRECTION (DC) FUNCTION
The TLC5948A can individually adjust the output current of each channel (OUT0 to OUT15) by using DC. The
DC function allows the brightness deviations of the LEDs connected to each output to be individually adjusted.
Each output DC is programmed with a 7-bit word, so the value is adjusted with 128 steps within the range of 0%
to 100% of I_OLCMax. Equation 2 calculates the actual output current value as a function of R_IREF, DC value, and
global BC value. DC data are programmed into the TLC5948A with the serial interface. When the device is
powered on, the DC data in the first and second control data latches contain random data. Therefore, DC data
must be written to the DC data latch before turning the constant-current outputs on. Table 2 summarizes the DC
data value versus the set current value.
BINARY
000 0000
000 0001
000 0010
—
111 1101
111 1110
111 1111
Table 2. DC Data versus Current Ratio and Set Current Value
DC DATA
DECIMAL
0
1
2
—
125
126
127
HEX
00
01
02
—
7D
7E
7F
BC DATA (Hex)
7F
7F
7F
—
7F
7F
7F
RATIO OF
OUTPUT
CURRENT TO
I_OLCMax (%)
0
0.8
1.6
—
98.4
99.2
100.0
I_OUT (mA)
(I_OLCMax = 45 mA,
typical)
0
0.35
0.71
—
44.29
44.65
45.00
I_OUT (mA)
(I_OLCMax = 2 mA,
typical)
0
0.02
0.03
—
1.97
1.98
2.00
GLOBAL BRIGHTNESS CONTROL (BC) FUNCTION
The TLC5948A has the ability to adjust the output current of all constant-current outputs simultaneously. This
function is called global brightness control (BC). The global BC for all outputs (OUT0 to OUT15) is programmed
with a 7-bit word. The global BC adjusts all output currents in 128 steps from 25% to 100%, where 100%
corresponds to the maximum output current set by R_IREF. Equation 2 calculates the actual output current as a
function of R_IREF, DC value, and global BC value. BC data can be set via the serial interface. When the device is
powered on, the BC data in the first and second control data latches contain random data. Therefore, BC data
must be written to the BC data latch before turning the constant-current output on.
The output current value controlled by DC and BC can be calculated by Equation 2.
I_OUTn = 1/4 ´
I_OLCMax +
3/4 ´ I_OLCMax ´ BC
127
DCn
´ ₁₂₇
Where:
I_OLCMax = the maximum constant-current value for each output determined by R_IREF
DCn = the dot correction value for each OUTn in the second control data latch (0h to 7Fh)
BC = the global brightness control value in the second control data latch (0h to 7Fh)
(2)
Copyright © 2012, Texas Instruments Incorporated
Product Folder Link(s): TLC5948A
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