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LM5119: Current Sinking Capability

Stephen Serlenga
Prodigy 170 points
Part Number: LM5119
Other Parts Discussed in Thread: TPS40170

I am currently designing a project where I need to supply and control Peltier modules. These require up to 10A with at 34V.


The plan is to use an LM5119 in dual channel mode with a pseudo H-bridge configuration (one side of the Peltier connects to VOUT1, the other side to VOUT2). This means that one of the channels at any given time will need to sink current. The question is, can the device sink this load current, will it be damaged, or will it go into protection mode? I see that page 18 of the datasheet states "the capability to sink current from the output in certain conditions such as light load, overvoltage, or prebias start-up.", but what is defined as light load?

Many thanks for your help.

  • 0
    TI__Mastermind 24075 points

    Hello,

    The light load means the inductor valley current is below zero.

    I don't think LM5119 can sink a 10A current, because the RAMP pin voltage can not emulate a negative inductor current. The loop will not be stable.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Prodigy 170 points
    Thank you for your response.

    I assume the current sense amplifier (pins CS and CSG) are unidirectional and cannot 'measure' a negative current. If this is the case, will the ramp compensation loop still be unstable when there is still output voltage present (minimum of around 10V), on the channel that has negative current (so 'sensed' current is zero)?

    Alternatively, can you recommend any devices that would be suitable for this task (can sink and source the full load current, or minimum of 5A)?

    Kind regards,

    Stephen
  • 0 in reply to Stephen Serlenga
    TI__Mastermind 24075 points
    Hi Stephen,

    I don't think the current sense amplifier and loop of LM5119 was designed work at high negative current condition.

    Probably a voltage mode controller is a better option, because only Vout is used for loop control. TPS40170 is a high voltage single phase voltage mode controller. If you are interested in TPS40170, you can submit a new thread. Someone from other team will support.

    Thanks
    Qian
  • 0 in reply to Qian Chen
    Prodigy 170 points
    Thanks for the advise.