TLC5902

LED DRIVER

SLLS382 – DECEMBER 1999

12

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

constant current output selection by user (80 mA

× 16 bits or 120 mA × 8 bits)

When MODE terminal is set to high, output is selected as 80 mA

× 16 bits. When MODE terminal is set to low,

output is selected as 120 mA

× 8 bits. By this setting, the internal shift register and latch are changed. Note that

two constant output terminals should be tied, such as OUT0 to OUT1 and OUT2 to OUT3 when 8-bit output is

selected.

MODE

OUTPUT

H

80 mA x 16 bits

L

120 mA x 8 bits

setting for constant current value

On the constant current output terminals (OUT0 to OUT15), approximately 38 times the current that flows

is calculated using the following equation.

I

(OUTn)

(mA)

^ 38

1.24(V)

R

More current flows if IREF is connected to GND directly.

shift register latch for gray scale data

The shift register latch for gray scale data is set as 8

× 8 bits configuration each at 8 bit mode, and as 16 x 8

bits configuration each at 16-bit mode. By setting RSEL to low, the shift register latch for gray scale data is

gray scale. The latched data is compared to GSCLK (clock for gray scale) counts, and constant current output

continues to turn on until these values are equal.

shift register latch for brightness control

The shift register latch for brightness control is configured with 1

× 8 bits each. The data input terminal and latch

terminal are common to shift register latch for gray scale data. By setting RSEL to low, the shift register latch

for gray scale data is selected, and by setting RSEL to high, the shift register latch for brightness control is

selected. If the brightness control function is not used, BC_ENA terminal should be pulled low. Since the

brightness control latch is reset to initial value of 00011111h, it is not necessary to write data to shift register latch

for brightness control. When power is up, latch data is undetermined. Data should be written to shift register

latch when the brightness control function is used. Also, rewriting the latch value for brightness control is

inhibited when the LED is turned on.

RSEL

SHIFT REGISTER LATCH SELECTED

L

Shift register latch for gray scale data

H

Shift register latch for brightness control

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