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I'm designing a power supply that I would like to have a USB power output for charging/powering USB devices.

In an effort to reduce risk and design time, I'm looking at mounting a DC/DC converter on my PCB. I'd like to be able to supply >= 2A to support fast charging applications and for future-proofing.

The cheapest converters that fit the bill seem to be point-of-load modules (e.g. http://uk.rs-online.com/web/p/non-isolated-dc-dc-converters/6894703/).

I understand that these are meant for powering known loads (FPGAs, DSPs etc.) internal to the design.

Are these modules suitable for powering "unknown" loads down a cable?

You may assume that I have taken care of the other considerations with regard to meeting USB charging specs etc. I'm only concerned at this stage with the suitability of these modules for supplying power.

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Yes, that module should be fine for powering USB. Volts are volts and amps are amps. Things to think about:

  • Many small power supply modules have a minimum load, below which they may become unstable. The one you linked doesn't, but there is a note in the datasheet that noise may be worse at low loads, so if you can spare some current you might want to add a resistor across the outputs.
  • This particular module has a decent amount of ripple even at higher loads, so a filtering capacitor might be a good idea - I can't remember what the USB spec requires in terms of ripple.
  • A capacitor on the input might also be required, depending where you're powering it from.
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  • \$\begingroup\$ Sounds reasonable to me. Do you know why point-of-load is explicitly mentioned then? It seems odd, that's all. It is just an "industry convention" thing now that multiple voltages are common? \$\endgroup\$
    – jfowkes
    Apr 19 '16 at 16:29
  • \$\begingroup\$ I always assumed that it was just a marketing thing. They are designed and optimised for that use. Some of them have minimum loads or restrictions on load capacitance which would make them poor general purpose supplies. \$\endgroup\$
    – Jack B
    Apr 20 '16 at 13:01
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Yes they will work with any load within the output specs.

This module provides 5V at 3A, so it can power like 6 standard USB devices (up to 500mA) or a fast-charging (5V 1A) with a good headroom for future super-fast chargers :)

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