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3.3V LDO Regulator / Power Supply Topology Advice — Parallax Forums

3.3V LDO Regulator / Power Supply Topology Advice

bradharperbradharper Posts: 64
edited 2011-08-04 08:02 in General Discussion
I'm looking to add a 5V rail to my project and will need to then step down from 5V-->3.3V for the propeller and peripherals.

I'm currently considering the NCP4589. Any thoughts for/against this choice or any other recommendations I should consider?

My power supply topology would be as follows:
6-15Vin --> LMZ12001 Switching Reg configured for 5V@500mA --> NCP4589 @ 3.3V --> Propeller etc.

My goal is for the switcher to manage the majority of the regulation as efficiently as possible and take the hit on the 5-3.3V drop.

Is this a solid approach?

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2011-08-03 20:44
    Much depends on what you are using that 5v for. If you are considering a mouse and keyboard, 500ma may not be enough. If you are just driving a few low power components, you will likely be okay. There are many, many regulators out there in the world. Picking a popular, readily available one might be best. I've no idea if the LMZ12001 or the NCP4589 are now in that league. Too many PDFs to read.
  • bradharperbradharper Posts: 64
    edited 2011-08-04 04:48
    The 5V supply is for an audio amp (LM4990 that the S2 uses) and that switcher can be configured for any output current up to 1A. What would you recommend as a popular 3.3V LDO?
  • max72max72 Posts: 1,155
    edited 2011-08-04 05:29
    Are you looking for a surface mount or a TH solution?
    Anyway check carefully the capacitors requirement and current rating. Probably current rating is not a big issue, but the capacitors are chip dependent, so datasheet handy...

    Check the boards available from parallax or gadget gangster. They have both types, and with a high current rating.
    For instance the propeller platform uses LD1086 or LD29150 depending on the mounting option.
    Parallax sells this one:
    http://www.parallax.com/Store/Components/IntegratedCircuits/VoltageRegulator/tabid/615/CategoryID/80/List/0/SortField/0/Level/a/ProductID/473/Default.aspx

    An SMD I used the TC1262, it is small and friendly (it requires small capacitors).

    Massimo
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2011-08-04 06:21
    While LDO is a good thing, so is reverse polarity protection and thermal overload protection.

    I believe the regulator on the Parallax Demo Board provides all three. You might take a look at the LM2939IMP-3.3. That may be just the surface mount version, but check the PDF for packages.
  • bradharperbradharper Posts: 64
    edited 2011-08-04 06:47
    I need SMD, and the smaller the better - I have very little space to work with. The LD1086 and TC1262 both look like candidates. I'll spend some time with these datasheets...

    Thanks for the info.
  • bradharperbradharper Posts: 64
    edited 2011-08-04 06:48
    Loopy Byteloose wrote: »
    While LDO is a good thing, so is reverse polarity protection and thermal overload protection.

    I believe the regulator on the Parallax Demo Board provides all three. You might take a look at the LM2939IMP-3.3. That may be just the surface mount version, but check the PDF for packages.

    Will do. The google hits on that one are interesting...
  • max72max72 Posts: 1,155
    edited 2011-08-04 07:06
    I haven't tested it, but the MCP1703T is very tiny (SOT-23A), 250mA.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2011-08-04 08:02
    The faster you clock and the more cogs you clock, the more milliamps you need. 250ma is a bit tight unless you are very clear on your purpose.
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