I am designing a product that will step down 12V to 5V in an automotive application. I am currently considering an MP1584 step down converter into an MIC29150 linear regulator. The MP1584 has a drop out of >2V which doesn't give me as much allowance as I would like for crank scenarios when the battery voltage drops. My preference is SOIC or DIP packages at present. Temp range -10 to 85 degC is fine.
Thanks in advance.
There are many consideration for a SMPS in an automotive application.
1) Operating temperature range
2) Drop-out voltage during engine cranking
3) Maximum input voltage in the likely event of load dump. (Is a 28V rated device enough?)
4) Is input path protected from reverse polarity if reversed jumper cables are connected.
5) EMI regulatory requirements such as CISPR 25 (and which level?) This may dictate switch frequency and EMI filter requirements.
Several of these subjects are covered in Ap note SNVA717 and the companion video. But This is still not everything you need, and does not cover EMI.
If you are using the linear regulator to "clean up" the HF residual noise of the SMPS; that approach usually doesn't work with budget performance LDOs). If the linear regulator is for an additional lower output voltage rail such as 3.3V then this is a different answer.
You might look at LM53603, LM43603, and LM46002 devices. But expect to add some EMI filtering with any SMPS device.
Alan Martin - Wide Vin Applications Wrangler
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