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LP5868: Chip_EN (register) setting during LED control setting change

Koshi Ninomiya
Expert 5495 points
Part Number: LP5868
Other Parts Discussed in Thread: LP5860EVM, LP5860

Tool/software:

Dear Team,

My customer evaluating the LM5860EVM to design the LP5868 application for their product.

There is a question about Chip_EN (register) setting during LED control setting change.
The LP5868 datasheet describes as below,

<LP5868 datasheet, page 14, 8.3.2 Analog Dimming (Current Gain Control)>
     For data refresh Mode 1, MC data is effective immediately after new data is updated. For Mode 2 and Mode 3, to avoid unexpected MC data change during high speed data refreshing, MC data must be changed when all channels are off and new MC data is only be updated when the 'Chip_EN' bit in Chip_en register is set to 0, and after the 'Chip_EN' returns to 1, the new MC data is effective.

When the 'Chip_EN' bit in Chip_en register is set to 0, the LP5868 will be set Standby mode. Under the Standby mode, can the LED control settings can be changed?

In case of the LP5860EVM with GUI, the user guide describes as below,

In the LP5860EVM with GUI, we cannot change the LED control settings unless we click the Enable button to enable the LP5860.

The LED control settings of the LP5868/LP5860 can only be changed while the chip is enabled, in Normal mode, right?

Best Regards,

Koshi Ninomiya

  • 0
    TI__Mastermind 20515 points

    Hi Koshi,

    Thanks for reaching out!

    Actually, the datasheet means that you can configure the MC bit during chip_en bit is 0 to avoid unexpected MC data change during high speed data.

    For your question:

    1. Under the Standby mode, can the LED control settings can be changed?

    The LED control setting will not be effect under standby mode.

    2. The LED control settings of the LP5868/LP5860 can only be changed while the chip is enabled, in Normal mode, right?

    Yes, it's correct.

    BR, Jared

  • 0 in reply to Jared Zhou
    TI__Expert 5495 points

    Hi Jared-san,

    Thank you for your reply. 
    Let me reconfirm, please.

    The LED control setting will not be effect under standby mode, and the LED control settings of the LP5868/LP5860 can only be changed while the chip is enabled, in Normal mode.

    However, why dose the datasheet describe that the MC data must be changed when all channels are off and new MC data is only be updated when the 'Chip_EN' bit in Chip_en register is set to 0?

    Best Regards,

    Koshi Ninomiya

  • +1 in reply to Koshi Ninomiya
    TI__Mastermind 20515 points

    Hi Koshi,

    Just like I said above, the datasheet means that you can configure the MC bit during chip_en bit is 0 to avoid unexpected MC data change during high speed data.

    It means the LED control setting of LP5860 can only be changed while the chip is enabled, but please distinguish between "the LED control setting of LP5860 is changed" and "the internal register map is changed".

    For example, if you configure the PWM or some other register in mode2 and mode3. it will not immediately be effect on output. So, the register map is configure successfully but the LED setting is not changed yet.

    BR, Jared