LP39542 Datasheet, PDF (21/58 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

RGB LED Blinking Control
LP39542 has a possibility to drive indicator LEDs with RGB1
outputs with programmable blinking time. Blinking function is
enabled with RGB_SEL[1:0] bits set as 01b in 0BH register.
R1_CYCLE_EN, G1_CYCLE_EN and B1_CYCLE_EN bits in
cycle registers (02H, 04H and 06H) enable/disable blinking
function for corresponding output. When EN_BLINK bit is
written high in register 11H, the blinking sequences for all
outputs (which has CYCLE_EN bit enabled) starts simulta-
neously. EN_BLINK bit should be written high after selecting
wanted blinking sequences and enabling CYCLE_EN bits, to
synchronize outputs to get desired lighting effect. R1SW,
G1SW and B1SW bits can be used to enable and disable
outputs when wanted.
RGB1 blinking sequence is set with R1, G1 and B1 blink reg-
isters (01H, 03H and 05H) by setting the appropriate OFF-ON
times. Blinking cycle times are set with R1_CYCLE[2:0],
G1_CYCLE[2:0] and B1_CYCLE[2:0] bits in R1, G1 and B1
CYCLE registers (02H, 04H and 06H). OFF/ON time is a per-
centage of the selected cycle time. Values for setting OFF/
ON time can be seen in following table.
R1, G1 and B1 Blink Registers (01H, 03H and 05H):
Name
R1_ON[3:0], R1_OFF[3:0]
G1_ON[3:0], G1_OFF[3:0]
B1_ON[3:0], B1_OFF[3:0]
Bit
7-4, 3-0
Description
RGB1 ON and OFF time
Bits
ON/OFF time
0000
0%
0001
1%
0010
2.5%
0011
5%
0100
7.5%
0101
10%
0110
15%
0111
20%
1000
30%
1001
40%
1010
50%
1011
60%
1100
70%
1101
80%
1110
90%
1111
100%
Blinking ON/OFF cycle is defined so that there will be first
OFF-period then ON-period after which follows an off-period
for the remaining cycle time that can not be set. If OFF and
ON times are together more than 100% the first OFF time will
be as set and the ON time is cut to meet 100%. For example,
if 50% OFF time is set and ON time is set greater than 50%,
only 50% ON time is used, the exceeding ON time is ignored.
If OFF and ON times are together less than 100% the re-
maining cycle time output is OFF.
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