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LM5169-Q1: current limit vs Rds on

Ernest Yong
Expert 4315 points
Part Number: LM5169-Q1
Other Parts Discussed in Thread: LM5168-Q1, LM34927, LM5169

Hi Team,

I have a customer who is interested in using LM5169-Q1 and were curious about the current limit.

From the data sheet, it mentions that the current limit is 0.7A while LM5168-Q1 is 0.35A, but both model have same high side or low side mosfet Rds on as shown in the screenshot below:

May I kindly check with you if the datasheet is correct? I think if we double the current, the resistance should become a quarter in order to make the same conduction loss. 

I compare with older model LM34927, that have same current limit : 0.7A, LM34927 high side and low side mosfet Rds on are around half LM5169-Q1 specifications, please see below:

Please help to verify about this.

Best Regards,

Ernest

  • +1
    TI__Guru 64365 points

    Hello

    The data sheet is correct. Both devices use the same FET sizes; only the current limit is changed.

    This allows the customer to select an inductor with a smaller current rating when using the lower current device.

    The FETs in the LM5169/8 family are designed for 120V operation.  Therefore, they will have a different Rdson compared

    to other devices of similar current rating and die size.

    Thanks