LMR36506-Q1: GPN selection for FSW=400k, Vout=5V

Daniel Wang (auto)

Part Number: LMR36506-Q1

Tool/software:

Hello team,

Customer is going to use LMR36506-Q1, but there is not a corresponding GPN for FSW=400k, Vout=5V work condition, pls check below screenshot, so which one should be used for the case?

Thanks!

9 months ago

0 Richard Fu22 9 months ago

TI__Mastermind 29375 points

Hi Daniel,

You will want to use the LMR36506RS3QRPERQ1, with the feedback resistors added to get the 5V and RT resistor for the 400kHz.

Thanks,

Richard

0 Daniel Wang (auto) 9 months ago in reply to Richard Fu22

TI__Expert 3010 points

Hello Richard,

Thanks for your reply, but I have some concerns:

LMR36506RS3QRPERQ1 is a 3.3V fixed variant, which means there is only VOUT/BIAS, but no FB function in pin8, and there is a resistor divider inside already, an additional resistor divider externally will cause inaccurate voltage. Is it right?

Customer could accept sourcing new inductor for 2.2M frequency, so if there is no exact variant for FSW=400k, Vout=5V, pls help explain it, thanks!

0 Daniel Wang (auto) 9 months ago in reply to Daniel Wang (auto)

TI__Expert 3010 points

Additionally, for 3.3V fixed variant, if external resistor is in series to achieve 5V output, I need to know internal resistors value, but I cannot find in datasheet.

Thanks.

0 Richard Fu22 9 months ago in reply to Daniel Wang (auto)

TI__Mastermind 29375 points

Hi Daniel,

Sorry for the mixup, I was confusing it with the non-q100 grade version of the device, which supports 5V output and adjustable frequency.

If customer is looking for Q100-grade device for 5V fixed output and 400kHz frequency, you are right- there is none. The closest is the LMR36506MSCQRPERQ1 (adjustable output, fixed 2p2MHz)

Thanks,

Richard

0 Daniel Wang (auto) 9 months ago in reply to Richard Fu22

TI__Expert 3010 points

Hi Richard,

Understood and thanks!

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LMR36506-Q1: GPN selection for FSW=400k, Vout=5V