LP55281TLSLASHNOPB datasheet(21/42 Pages) TI2

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LP55281

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SNVS458D – JUNE 2007 – REVISED OCTOBER 2016

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7.3.4.1 LED Test Procedure

An example of LED test sequence is presented here. Note that user can use incremental write sequence on I2C.

The test sequence consists of the basic setup and measurement phases for all RGB LEDs and boost voltage.

Basic setup phase for the device:

1. Give reset to LP55281 (by power on, NRST pin or write any data to register 60h)

2. Set the preferred value for RED1 (write 3Fh, 7Fh, BFh or FFh to register 00h)

3. Set the preferred value for GREEN1 (write 3Fh, 7Fh, BFh or FFh to register 01h)

4. Set the preferred value for BLUE1 (write 3Fh, 7Fh, BFh or FFh to register 02h)

5. Set the preferred value for RED2 (write 3Fh, 7Fh, BFh or FFh to register 03h)

6. Set the preferred value for GREEN2 (write 3Fh, 7Fh, BFh or FFh to register 04h)

7. Set the preferred value for BLUE2 (write 3Fh, 7Fh, BFh or FFh to register 05h)

8. Set the preferred value for RED3 (write 3Fh, 7Fh, BFh or FFh to register 06h)

9. Set the preferred value for GREEN3 (write 3Fh, 7Fh, BFh or FFh to register 07h)

10. Set the preferred value for BLUE3 (write 3Fh, 7Fh, BFh or FFh to register 08h)

11. Set the preferred value for RED4 (write 3Fh, 7Fh, BFh or FFh to register 09h)

12. Set the preferred value for GREEN4 (write 3Fh, 7Fh, BFh or FFh to register 0Ah)

13. Set the preferred value for BLUE4 (write 3Fh, 7Fh, BFh or FFh to register 0Bh)

14. Set the preferred value for ALED (write 01h - FFh to register 0Ch)

15. Dummy write: 00h to register 0Dh (Only if the incremental write sequence is used)

16. Dummy write: 00h to register 0Eh (Only if the incremental write sequence is used)

17. Set preferred boost voltage (write 00h - FFh to register 0Fh)

18. Set preferred boost frequency (write 00h - 07h to register 10h, PWM frequency can be anything)

19. Enable boost and RGB drivers (write CFh to register 11h)

20. Wait 20 ms for the device and boost start-up

Measurement phase:

1. Enable LED test and select output (write 1xh to register 12h)

2. Wait for 128 µs

3. Read ADC output (read register 13h)

4. Go to step 1 of measurement phase and define next output to be measured as many times as needed

5. Disable LED test (write 00h to register 12h) or give reset to the device (see step 1 in basic setup phase)

7.3.4.2 LED Test Time Estimation

Assuming the maximum clock frequencies used in SPI or I2C-compatible interfaces, Table 9 predicts the overall

test sequence time for the test procedure shown above. This estimation gives the shortest time possible.

Incremental write is assumed with I2C. Reset and LED test disable are not included.

Table 9. LED Test Time

TEST PHASE

TIME (ms)

I2C

SPI

Setup

0.528

0.024

Boost start-up

14 measurements

4.137

1.831

Total time

24.7

21.9

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