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TPS54560B: Evaluation for LiFePO4 Battery-Powered Laser System

Alessandro Maio
Prodigy 10 points
Part Number: TPS54560B
Other Parts Discussed in Thread: TPS54540B-Q1, , LM65645

Tool/software:

Hi Team,

I’m currently using the TPS54540B-Q1 in a well-established laser power management project that requires approximately 4A output current. The input voltage is a stable 36V supplied by a standard wall-powered supply.

Due to customer requirements, I’m now considering a redesign using the TPS54560B to enable the system to tolerate a maximum input voltage of around 59V. The updated design would power the same laser box, but this time using a 48V LiFePO4 battery instead of the previous wall-plugged supply.

Here’s the battery voltage profile:

State Voltage
100% (charging) -> 58.4V
100% (rest) -> 54.4V
90% -> 53.6V
80% -> 53.1V
70% -> 52.8V
60% -> 52.3V
50% -> 52.2V
40% -> 52.0V
30% -> 51.5V
20% -> 51.2V
10% -> 48.0V

Given that the battery voltage ranges from 58.4V down to 48V, I’d like to ask if you foresee any major issues using the TPS54560B with this variable input. In your opinion, is the TPS54560B output reliable across this voltage range?

Thanks in advance,
Best Regards,
Alessandro

  • 0
    TI__Genius 13916 points

    Hello Alessandro

    it's not recommended to use a 60V converter for 59V input. There isn't enough margin for reliable operation. I would recommend using 75V or 80V to provide a sufficient margin.  

    If your 59V rail is well-regulated and you don't anticipate any voltage transients, a 65V converter with a 70V absolute maximum rating could be considered.

    For potential alternatives, you can take a look at LM65645, LM70840 

    Thank you

    Regards

    Onkar Bhakare

  • 0 in reply to Onkar Bhakare
    Prodigy 10 points

    Thank you for the prompt reply, Onkar, and many thanks for your suggestions regarding alternative components. I have a couple more questions, if possible:

    -How should I calculate the margin to ensure correct operation? Is it strictly related to the input voltage (Vin), or should I also consider the output voltage I need to achieve? For example, in my case, the system is configured to deliver approximately 28V output. Given this setup, would a 60V input still be acceptable?
    (Just to be 100% clear: for the TPS54560B, the Vin will be a maximum of 58.4V, while the output will be set around 29V.)

    -Could you please clarify what you meant by: "If your 59V rail is well-regulated and you don't anticipate any voltage transients"? What I need is to ensure reliable operation while the battery voltage naturally drops during discharge.

    -If I were to switch to another product such as the LM65645, would it handle the battery voltage drop without significant issues?

    Thanks again for your support.

    Best regards,
    Alessandro

  • 0 in reply to Alessandro Maio
    TI__Genius 13916 points

    Hello Alessandro,

    I was mentioning about the margin between your 58.4V input and the TPS54560B’s absolute maximum rating, it’s approximately 5V.

    The inductance of the wiring harness and PCB traces between the supply input and the device, combined with the input capacitance, can create LC oscillations during transients. These oscillations can briefly exceed the absolute maximum rating at the device input pin, even if the steady-state voltage remains within the specified limit. These possess risk from reliability point of view.

    With 59V input, 28V output is quite possible, and there isn't big concern from output voltage point of view. However, margin between input voltage and abs max of the device is quite low

    Regards

    Onkar Bhakare