TLC5902_05 Datasheet, PDF (13/23 Pages) Texas Instruments – LED DRIVER

PRINCIPLES OF OPERATION
TLC5902
LED DRIVER
SLLS382 – DECEMBER 1999
write data to both shift register latches
The shift register latch is selected using the RSEL terminal. The data input method is the same for both shift
register latches. The data is applied to DIN0 to DIN7 of 8-bits data input terminal, and transferred synchronizing
to DCLK. The data of DIN0 to DIN7 is transferred to the direction from OUT0 to OUT15 synchronizing to DCLK.
The shift register for brightness control is 1-bit length resulting in one time of DCLK input. The shift register for
gray scale data is 8-bits length at 8-bit mode resulting in eight times of DCLK, and 16-bit length at 16-bit mode
resulting in 16 times of DCLK input. At the number of DCLK input for each case, output data appear on DOUT0
to DOUT7. When LATCH goes from low to high, data is latched internally. Then, when LATCH goes low, data
is held. RSEL switching should be done when DCLK and LATCH are low.
brightness control latch configuration
The brightness control latch is configured as DIN0 corresponds to LSB, and DIN7 to MSB. The lower 5 bits are
assigned for output current adjustment, and the upper 3 bits are for a frequency division ratio setting of GSCLK.
DIN7
MSB
0†
DIN6
⋅ ⋅⋅⋅
0
DIN5
⋅ ⋅⋅⋅
0
Frequency division ratio setting of GSCLK
† _{BC_ENA is low.}
DIN4
⋅ ⋅⋅⋅
1
DIN3
⋅ ⋅⋅⋅
1
DIN2
⋅ ⋅⋅⋅
1
Output current setting
DIN1
⋅ ⋅⋅⋅
1
DIN0
LSB
1
output current adjustment – brightness adjustment between ICs
By using the lower 5 bits of the brightness control latch, output current can be adjusted to 32 steps. When output
current is set to 100% by the external resistor at 11111h of the latched value, it is adjusted as 1 step or 32 steps
of 1.6% current ratio between 100 and 51.6%. By using this function, the brightness control between modules
(ICs) can be adjusted, sending the desired data externally even if ICs are mounted on PCB. When BC_ENA
is pulled low, the latch is reset to the initial value of 00011111h, and the output current is set to 100%.
CODE
MSB 00000 LSB
⋅
⋅
⋅
⋅
11110
11111†
† _{BC_ENA is low.}
CURRENT RATIO (%)
51.6
⋅
⋅
⋅
⋅
98.4
100
20 (mA)
10.3
⋅
⋅
⋅
⋅
19.7
20.0
80 (mA)
41.3
⋅
⋅
⋅
⋅
78.7
80.0
VIREF (TYP)
0.64
⋅
⋅
⋅
⋅
1.22
1.24
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