TLC5958 Datasheet, PDF (17/28 Pages) Texas Instruments – TLC5958 48-Channel, 16-Bit ES-PWM LED Driver with Pre-Charge FET, LED Open Detection and Display Data Memory Support 32-Multiplexing

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TLC5958
SLVSCE7A – MAY 2014 – REVISED SEPTEMBER 2014
Device Functional Modes (continued)
Table 1. CC Data vs Current Ratio and Set Current Value
CC DATA (CCR or CCG or CCB)
BINARY
0 0000 0000
0 0000 0001
0 0000 0010
---
1 0000 0000
(Default)
---
1 1111 1101
1 1111 1110
1 1111 1111
DECIMAL
0
1
2
---
256
(Default)
---
509
510
511
HEX
00
01
02
---
100
(Default)
---
1FD
1FE
1FF
RATIO OF OUTPUT
CURRENT
TO I_olcMax(%, typical)
OUTPUT CURRENT (mA, R_IREF = 7.41 kΩ)
BC = 7h
(IolcMax =25mA)
BC = 0h
(IolcMax=3.2mA)
0
0
0
0.2
0.05
0.006
0.4
0.10
0.013
---
---
---
50.1
12.52
1.621
---
99.6
99.8
100.0
---
24.90
24.95
25
---
3.222
3.229
3.235
10.3.3 Select R_IREF For a Given BC
The maximum output current per channel, I_OLCMax, is determined by resistor R_IREF, placed between the IREF and
IREFGND pins, and the BC code in FC1 register. The voltage on IREF is typically 1.209V. R_IREF can be
calculated by Equation 2.
Riref(kΩ) = Viref(V) / IOLCMax(mA) × Gain
(2)
Where:
V_IREF = the internal reference voltage on IREF (1.209V, typical)
I_OLCMax is the largest current for each output at CCR/G/B=1FFh.
Gain = the current gain at a selected BC code (See Table 2 )
Table 2. Current Gain Versus BC Code
BINARY
BC DATA
HEX
GAIN
RATIO OF
GAIN / GAIN_MAX (AT MAX
BC)
000 (recommend)
0 (recommend
20.4
12.9%
001
1
40.3
25.6%
010
2
59.7
52.4%
011
3
82.4
12.9%
100 (default)
4 (default)
101.8
64.7%
101
5
115.4
73.3%
110
6
144.3
91.7%
111
7
157.4
100%
NOTE: Recommend using a smaller BC code for better performance. For noise immunity purposes, suggest R_IREF < 60 kΩ
10.3.4 Choosing BC/CC For a Different Application
BC is mainly used for global brightness adjustment between day and night. Suggested BC is 4h, which is in the
middle of the range, thus, one can change brightness up and down flexibly.
CC can be used to fine tune the brightness in 512 steps, this is suitable for white balance adjustment between
RGB color group. To get a pure white color, the general requirement for the luminous intensity ratio of R, G, B
LED is 3:6:1. Depending on the characteristics of the LED (Electro-Optical conversion efficiency), the current
ratio of R, G, B LED will be much different from this ratio. Usually, the Red LED needs the largest current. One
can choose 511d (the max value) CC code for the color group that needs the largest initial current, then choose
proper CC code for the other two color groups according to the current ratio requirement of the LED used.
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