TLC5910

LED DRIVER

SLLS392 – NOVEMBER 1999

16

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

brightness control function

By writting data into the brightness control latch, the current on all constant current outputs can be adjusted to

control the variation of brightness between ICs and the division ratio for the gray scale clock can be set to control

the variation of brigtness for the total panel system. Furthermore, by writing data into the dot correction latch,

the current on each constant current output can be adjusted.

output current adjustment on all constant current outputs – brightness adjustment between ICs

By using the lower 6 bits of the brightness control latch, the output current can be adjusted to 64 steps. 1 step

of 0.8% current ratio between 100% and 50.8% when the set output current is 100% by an external resistor (note

that the current value is lower if the constant current output is corrected using the dot correction function). By

using this function, the brightness control between modules (ICs) can be adjusted sending the desired data

externally even if the ICs are mounted on a print-circuit board. When BCENA is pulled low, output current is set

to 100%.

Table 2. Relative Current Ratio For Total Constant Current Output

CODE

CURRENT RATIO

(%)

20

(mA)

80

(mA)

VIREF

(TYP)

MSB 000000 LSB

50.8

10.2

40.6

0.61

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

111110

99.2

19.8

79.7

1.20

111111†

100

20.0

80.0

1.21

† BCENA is low.

frequency division ratio setting for gray scale clock – panel brightness adjustment

By using the upper 4 bits of the brightness control latch, the gray scale clock can be divided into 1/1 to 1/16.

If the gray scale clock is set to 16 times the speed (1024

×16=16384) of frequency during horizontal scanning

time, the brightness can be adjusted to 16 steps selecting the frequency division ratio. By using this function,

the total panel brightness can be adjusted at once, and it applies to the brightness of day or night circumstances.

When BCENA is pulled low, the gray scale clock is not divided. When BCENA is pulled high, the brightness can

be adjusted (see Table 3).

Table 3. Relative Brightness Ratio For Total Constant Current Output

CODE

FREQUENCY

DIVISION RATIO

RELATIVE BRIGHTNESS RATIO

(%)

MSB 0000 LSB†

1/1

6.3

.

.

.

.

.

.

.

.

.

.

.

.

1110

1/15

93.8

1111

1/16

100

† BCENA is low.