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LM5155-Q1: Does LM5155-Q1 need to use CS pin?

Soichi Nishimura
Expert 5215 points
Part Number: LM5155-Q1
Other Parts Discussed in Thread: LM5155

Hi team,

I have a question to CS pin of LM5155-Q1.

Does LM5155-Q1 need to use CS pin? If LM5155-Q1 doesn't need to use CS pin, how to terminate the CS pin of LM5155-Q1?

Regards,

Nishimura

  • 0
    TI__Mastermind 46905 points

    Nishimura

    experts supporting this device is out of office. they will reply you next week

  • 0 in reply to Jasper Li
    TI__Expert 5215 points

    Hi team,

    Could you support this question? 

    Regards,

    Nishimura

  • 0 in reply to Soichi Nishimura
    TI__Guru* 78270 points

    Hi Soichi,

    The LM5155 is the current mode PWM controller.  It relies on the CS signal to generate PWM, so the CS pin should always be used for current sensing.  I don't understand why you want to give up the CS pin.

    If you really have some special reason, then you may terminate the CS pin by a few kOhm resistor to GND. This will change the control mode to voltage mode.  The resistor will generate a ramp signal by the internal slope current source, but the resistor value should be also be limited to prevent trigger the peak current limit threshold.  Theoretically this should work but the control loop requires a Type-III compensation.  And note that, such configuration has never been fully tested by us, so there may be, and may not be, some unexpected behaviors, which we may not be able to support and resolve, because of the use of the part in non-recommended configuration.   

    Thanks,

    Youhao Xi,  Applications Engineering