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LP5569: Difference in power consumption when operating with external clock

Part Number: LP5569

Hi there,

When going through the LP5569 datasheet, I read at 8.5.2.3 that "Using an external clock enables synchronization of LED timing to the external clock signal and is also more power-efficient".

However, I couldn't understand how much more efficient it is to use external CLK, and some data (shown below) leads me to believe that internal CLK is equally or more efficient then external CLK.

I'd like to better understand the advantages of using external CLK in order to decide whether or not to use it in my custom pcbs. Is it more power efficient? If yes, in what case(s)?

Thanks in advance for your support,

Bruno  

  • Hi Bruno,

    Please refer to the 8.4 chapter on the datasheet of LP5569, which describe the various modes of operation. The table you marked shows IVIN under different operation modes and during standby/power-save mode there is no current in the LED OUTx pins, so no different between external clock running and internal oscillator. figure 8 also shows the different under power-save mode. 

    The advantage of external clock will be reflected in normal mode.

    Best Regard 

    Monet Xu

  • Hi, Monet.

    Could you explain more about the difference in power consumption?
    Would you have any estimation with the LED ON?

    We are trying to evaluate the advantages of the external clock, we couldn't figure out by the datasheet.

    Thanks!

  • Hi Mauricio,

    Sorry for late reply. Monet is out of office and I will help to answer your question. Here is some current consumption value I tested in EVM board. It includes consumption for on-board LDO so the value is larger than datasheet. The consumption would increase around 0.28mA with external clk signal.

    This 32kHz signal is the execution clock for engine codes. As we know there are some variation for internal oscillator frequency of different units, due to manufacture process. When there are multi LP5569 using internal engine to perform animation, they may have some difference after running long time due to the different execution clock. So with the same external clock source, they can display animation totally synchronized.

    Iin / mA no external CLK with external CLK
    EN on; Chip_en = 0 0.0279 0.302
    EN on; Chip_en = 1 0.269 0.542
    one channel PWM = 0xFF 17.589 17.861
    all channels PWM = 0xFF 215.57 215.84
  • Awesome, Wu. Thanks for the testing!

    In our application we intend to use 2 LP5569 to create patterns. As it is a battery powered device, the best approach (if the columns are not swapped) to use the internal clock of the first one as reference and synchronize the other one using the CLK pin. Is this approach correct?

    In the case of an external clock, would you have any recommendation? 

  • Hi Mauricio,

    Yes you can set the CLK pin as output in register 0x3D bit 3 of first IC.

  • Hi Hardy Wu, thanks a lot for helping

    So the conclusion is that using internal clock consumes less power than external clock. Is this right?

    Thanks!

  • Hi Bruno,

    Yes. Using internal clock could save some power, comparing with external clock.