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LMZ31530: Behaviour when output current greater than 30A but less than internal limit of 40A

Gavin Teague
Intellectual 275 points
Part Number: LMZ31530 
This part is rated for an output current from 0 to 30A. It has an internal current limit threshold of 40A (typical). We would like to find out the behaviour of this device between 30A and 40A.

1) In other words, how will the device behave if the current is greater than 30A but less than that required to trigger the internal current limit threshold of 40A?

2) If the device has significant cooling so that the junction temperature does not approach the thermal shutdown limit of 145C, is it safe to operate the device in this region (above 30A and below internal current limit of 40A)?

Thank you.
  • 0
    TI__Guru 50120 points

    Hi Gavin,

    Any current at or above the current limit threshold will trip overcurrent protection and result in a cycle-by-cycle overcurrent limiting control.(hiccup mode) that you can see on Figure 26/27. It is recommended to have the device run under the recommended maximum output current in Section 4.5 Electrical Characteristics. However, as far as application purposes, the device should still be switching and providing an output voltage assuming the combination of input/output voltage and load current doesn't push the device pass the 125degC junction temperature and result in thermal shutdown. Proper thermal control and PCB copper area design should be taken into account when running high currents. 

    Regards,

    Jimmy