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LM5060: LM5060: Protect overcurrent protection function from short circuit.

Nobbi1707
Prodigy 100 points
Part Number: LM5060
Other Parts Discussed in Thread: LM5069

Hello,

we want to use the LM5060 to switch off the motor power when the current flow to the motor exceed a defined current (let us say 23 A) for a defined time (let us say 2ms).

In the Forum I have seen a problem from another user, that the LM5060 has problems with short circuits on output side.

In my application we must also calculate with schort circuits on output side and we must switch off the output in a safe way imidialtely.

I want to protect the VIN input with a diode from input voltage to the VIN input and a capacitor from VIN input to GND. This shall hold energie to let the LM5060 operate to switch of the MOSFET.

In the data sheet i can not see that the LM5060 will operate when the VIN voltage is less than the SENSE input voltage and the output voltage.

I would assume that this will work, but i want to ask if some experience exists if this will work.

Would be happy abou a fast response.

  • 0
    TI__Guru** 105361 points

    Hi,

    Thanks for reaching out.

    As mentioned in Section "8.1.5 Overcurrent Fault" of the datasheet, LM5060 does not provide short circuit protection. I suggest to use LM5069 for this application. Please let me know if you have followup questions.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Prodigy 100 points

    Hello,

    thanks for the fast response.

    That is correct that the component is not specified for short circuit protection, but a short circuit is also above the current limitation. The only point is that the short circuit will cut also the power for the LM5060 and the LM5060 will stop working.

    Your suggestion with the alternative component is ok but this will increase the circuit with a big current measurement resistor which have additional power dissipation which needs cooling. But in our application we have to reduce product volume which request to reduce the power dissipation and components which are not necessary. I see the possibility with the LM5060 where the current measurement resistor ist the R_on of the MOSFET. Sure, the mesasurement is not so precise, but possible. We have find possibly a solution to help the LM5060 to withstand the short circuit till the MOSFET switches off. I want to know if there is any restriction which will fail my solution to withstand the short circuit. Or is there a better way except to increase the volume and power dissipation.

    Would be great to get an answer soon.

    Best regards

    Norbert

  • 0 in reply to Nobbi1707
    TI__Guru** 105361 points

    Hi Norbert,

    LM5060 response is in the order of 10us for short circuit event. If there isn't enough impedance in the path to limit the fast rising short circuit current, the input bus voltage can collapse. The huge current can also stress the external MOSFET.

    It is acceptable for systems having large input inductance which can limit the di/dt of short circuit current or systems having metal fuse is series which could open up to protect the MOSFET from getting damaged.

    Best Regards, Rakesh