TLC5955 Datasheet, PDF(28/53 Page) Texas Instruments – TLC5955 48-Channel, 16-Bit, PWM LED Driver with DC, BC, LED Open-Short Detection, and Internal Current Setting

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TLC5955 Datasheet, PDF (28/53 Pages) Texas Instruments – TLC5955 48-Channel, 16-Bit, PWM LED Driver with DC, BC, LED Open-Short Detection, and Internal Current Setting

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TLC5955

SBVS237 â MARCH 2014

www.ti.com

8.4 Device Functional Modes

8.4.1 Maximum Current Control (MC) Function

The maximum output current per channel, IOLCMax, is programmed by the MC data and is set with the serial

interface. IOLCMax is the largest current for each output. Each OUTXn sinks the IOLCMax current when they turn on

and the dot correction and global brightness control data are set to the maximum value of 7Fh (127d).

When the device is powered on, the MC data are set to 0. MC data should be changed when all constant-current

outputs (OUTXn, where X = R, G, or B; n = 0 to 7) are off. MCX = 6 and MCX = 7 are used when VCC is greater

than 3.6 V. The same MC data must be written twice to change the maximum constant-current output. Table 8

shows the characteristics of the constant-current sink versus the maximum current (MC) control data.

BINARY

000 (default)

001

010

011

100

101

110 (3)

111 (3)

Table 8. Maximum Constant-Current Output versus MC Data

MCX(1) DATA

DECIMAL

HEX

IOLCMax (mA), OUTXn(2)

0 (default)

3.2

8.0

11.2

15.9

19.1

23.9

27.1

31.9

(1) X = R, G, or B.

(2) X = R, G, or B. n = 0 to 15.

(3) MCX7 and MCX6 can be used when VCC is greater than 3.6 V.

8.4.2 Dot Correction (DC) Function

The TLC5955 can individually adjust the output current of each channel (OUTx0 to OUTx15, where x is R, G, or

B) 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 26.2% to 100% of IOLCMax. DC data are programmed into the TLC5955 with the serial

interface. When the device is powered on, the DC data in the control latch contains random data. Therefore, DC

data must be written to the DC data latch before turning the constant-current outputs on. Table 9 summarizes the

DC data value versus the set current value.

BINARY

000 0000

000 0001

000 0010

111 1101

111 1110

111 1111

Table 9. DC Data versus Current Ratio and Set Current Value

DCXn(1) DATA

DECIMAL

HEX

BC DATA (Hex)

RATIO OF

OUTPUT

CURRENT TO

IOLCMax (%)

26.2

IOUT (mA)

(MC = 7, typical)

8.36

26.7

8.54

27.3

8.73

125

98.8

31.5

126

99.4

31.7

127

100.0

31.9

IOUT (mA)

(MC = 0, typical)

0.84

0.86

0.88

3.16

3.18

3.20

(1) X = R, G, or B. n = 0 to 15.

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