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LM27402: LM27402 how to disable or remove C+ and C1 if no used

Red Yen
Expert 4310 points
Part Number: LM27402

Hi Support team 

since LM27402 is voltage mode control which means the current sense is for protection only  

my question is that if C+ and C1 if no used , may I connect to GND directly? any side effect?

  • 0
    TI__Mastermind 21755 points

    Red,

    Based on the datasheet, current sensing is only for overcurrent and short circuit protection. It is recommended to use these pins to enable the protection features. Current limit is not internally set to any default value as such so if there is a surge of current during startup or during normal operation, the IC will not be protected against it.

    Based on the internal block diagram, a 10uA current source from VIN drives the CS- pin. As long as the CS+:CS- comparator does not trip, the overcurrent and short circuit protection feature should be disabled. A resistor (let's say 10kohm) on the CS- pin to GND while grounding CS+ that can keep the differential voltage from CS+ to CS- negative enough may work - make sure to not exceed the voltage rating on these pins as well as the differential voltage range as mentioned in datasheet on table 6.1. This suggestion is just based on the expected internal operation and a basic SPICE simulation - this has not been tested and verified across all corners of IC operation as not using CS pins is not recommended. You will need to thoroughly test on an evaluation board to ensure this operation works as intended for your application.

    On another note, why are you considering not using the current sense scheme? What is the VIN, VOUT and IOUT range that you intend to run your application at? Perhaps, a  different IC may work better for your needs. Let us know.

    Regards,

    Amod