LTC4079 Linear Battery Charger

Hi,

I am using LTC4079 in the battery backup system of my design to charge Li-Ion batteries. The input and output voltages of LTC4079 are 24 V and 4.2 V, respectively. If there are fluctuations in the input voltage, let's say it drops down to 16V from 24 V, will it have any affect on the output voltage? Will the output voltage stay constant? 

Thank you 

Regards,

Paul

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  • +1
    •  Analog Employees 
    on Apr 4, 2019 6:01 PM over 1 year ago

    Hi Paul,

    It depends on how fast the input changes. If it is a very fast drop, there may be a momentary change in the output voltage, but it will likely be very small. You can remedy this with more output capacitance if necessary. I would advise that you proceed with your design as-is and test for this when you can. If there proves to be a noticeable change in the output voltage at that event, we can look into a solution together.

    Alternatively, you could test this out with an LTC4079 demo board sooner. However, my guess is that you will not have an issue here.

    Regards,

    Zack

  • Hi Zack,

    Thank you for a prompt response. What do you think if there are small fluctuations in input voltage, let's say +/- 0.5 V of 24 V? 

    Paul

  • 0
    •  Analog Employees 
    on Apr 4, 2019 8:15 PM over 1 year ago in reply to BrarP

    Hi Paul,

    Smaller fluctuations would mean smaller effect on the output. Still, the speed of the step will influence whether there is any change in the output.

    Adding cap on the input will slow the step speed whereas adding cap on the output will dampen changes in the regulation voltage up to a point. If you do observe any issue, you could experiment with both.

    Regards,

    Zack

Reply
  • 0
    •  Analog Employees 
    on Apr 4, 2019 8:15 PM over 1 year ago in reply to BrarP

    Hi Paul,

    Smaller fluctuations would mean smaller effect on the output. Still, the speed of the step will influence whether there is any change in the output.

    Adding cap on the input will slow the step speed whereas adding cap on the output will dampen changes in the regulation voltage up to a point. If you do observe any issue, you could experiment with both.

    Regards,

    Zack

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