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TPS548A29EVM: Remote sense in TPS548A29EVM

Tim Peng
Prodigy 150 points
Part Number: TPS548A29EVM
Other Parts Discussed in Thread: TPS40400

Tool/software:

Hi Support 

According to TPS548A29EVM use guide(https://www.ti.com/lit/ug/slvubn8/slvubn8.pdf?ts=1757324720165&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FTPS548A29EVM)

it says to replace R8 and R11 with 100 ohm.  Could you help to explain what is the reason? and why 100 ohm? 

  • 0
    TI__Genius 15117 points

    Hi Tim, 

    When using remote sense, usually two small resistors of the same place are placed at the positive and negative sense points to ensure the small offset is the same between the two points. Also, in case that one of the sense lines is disconnected from the remote measuring point, the device may think that there is a drop and try to increase the voltage to overcompensate. This may damage the device, but having the 100 ohm resistor will at least limit the current to prevent damage. 

    Best,

    Ryan

  • 0 in reply to Ryan Chen
    Prodigy 150 points

    Hi Ryan, 

    When you mentioned "When using remote sense, usually two small resistors of the same place are placed at the positive and negative sense points to ensure the small offset is the same between the two points."  

    Do you know if there is any application note that explains those considerations? I don't understand what it means by " small offset". And I also wonder if I can use some other value like 0 ohm placed at the positive and negative sense points?   

    I also see some other recommendations found in "TPS40400 datasheet" , it says "Values between 10Ω to 50Ω are usually chosen.". It sounds like it is a rule of thumb. no exact way to calculate the value. 

  • +1 in reply to Tim Peng
    TI__Genius 15117 points

    Hi Tim, 

    Placing small values 10-100ohm is okay. Using 0 ohm is okay as well. The first thing is to make sure that both the positive and negative resistor value is the same. 

    Remote sensing for power supplies

    Using a value that is not 0 (10, 50, 100) is used as a fail-safe in case the remote sense is disconnected from the remote load while the device is on. This limits the current in case the device tries to overcompensate. 

    Best,

    Ryan

  • 0 in reply to Ryan Chen
    Prodigy 150 points

    Thanks for sharing your perspectives.