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LM3488: 100% duty cycle buck

David Ellis
Prodigy 185 points
Part Number: LM3488
Other Parts Discussed in Thread: LM5085, LM5145

Is the LM3488 suitable to configure a 100% duty cyce buck?    Here are the following customer requirements:

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  1. "Need to step down from 12V and need to be able to have Vout = Vin (understand not possible due to RDS on and inductor resistance) but would like to have 100% duty cycle capable. 

  2. Nominal Vin is 12V +/- 10%.    Vout = Vin and digitally controlled down to anything lower (will use a digital POT as the feedback element).

  3. Regulation tolerance is not that important but would prefer a higher freq. of operation to keep inductor size reasonable. 

 Vin =  4V min  to 17V max

Vout = ~ Vin …..100% duty cycle capable

Iout =  5Amps

 a suggestion to an alternate controller would be appreciated if  LM3488 is not a good fit  "

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  • 0
    TI__Guru* 78110 points
    For buck you really need a high side driver. Our previous product line has 100% duty buck (LM5085) but is a converter having limited power not able to support your 5A. The buck controller to support min drop out is the LM5145. You may post under LM5145 and you will be guided to the Buck product line for appropriate support.