0
\$\begingroup\$

I am selecting a 3.3V output switching regulator (to power the MCU, LEDs, and some ICs) for a project and I am noticing that even after specifying a specific list of parameters that I am looking for in the component, there is a wide range in cost. I am seeing pricing ranging from as low as $0.30 and up to like $8; and everything in between. I don't want to go with the "cheapest" option since the switching regulator is an important component...but I also don't think I need a $3 regulator.

Some things that I think impact the price are package size and the number of external components required, but even still, from what datasheets I have gone through, I cannot fully confirm my hypothesis as to what impacts price. Obviously big name brand components are not the cheapest. Maybe efficiency and ripple impact the price as well? I don't have time to go through EVERY datasheet though and come up with the answer and unfortunately some of these parameters are not listed when just doing the component searches on digikey or mouser.

If anyone with a lot of experience with different switching regulators could shed some light on this, that would be awesome!

Here are some examples...

On the cheaper side, this Diodes Inc regulator is $0.45 https://www.mouser.com/datasheet/2/115/AP65211A-1143084.pdf

This TI regulator is $1.68 http://www.ti.com/lit/ds/symlink/tps54202h.pdf

Update:

The capability of synchronizing seems to play a big factor. Switching frequency and package size seem to be the main other driving factors.

\$\endgroup\$
4
  • 3
    \$\begingroup\$ Pop in the specs, prices and links for two that you've identified as being suitable but differing substantially in price. Someone will give the low-down. \$\endgroup\$
    – Transistor
    Commented Sep 12, 2018 at 19:38
  • 3
    \$\begingroup\$ Switching freq will impact inductor and capacitor size, I'm not sure but it could be that generally faster switching ICs are more expensive. So very roughly if PCB space is at a premium it would make sense to go for ICs which allow smaller components. \$\endgroup\$
    – Wesley Lee
    Commented Sep 12, 2018 at 19:39
  • 3
    \$\begingroup\$ Just to add: (a) All external IC pins cost money. More pins, more cost. (b) Boutique parts (unique to one manufacturer and newer) are often higher cost without necessarily adding value for your application. (c) Frequency of operation -- there is a "sweet spot" here so it's not so simple as "higher is better." At some point, other difficulties add other increasing costs. (d) Don't buy function you don't need. \$\endgroup\$
    – jonk
    Commented Sep 12, 2018 at 19:54
  • \$\begingroup\$ Ok I actually was missing the "synchronous" parameter. That appears to be a big difference maker. As well as switching frequency. A follow up question: if I am stepping down the supply voltage to 9V and 3.3V on the board, would it be ok to use the same variable switching regulator for both, just configured differently? Or is it not recommended to use switching regulators with the same switching frequency? \$\endgroup\$
    – zme
    Commented Sep 12, 2018 at 19:59

2 Answers 2

Reset to default
2
\$\begingroup\$

And why wouldn't you go with the cheapest part that meets all the requirements. If you think there's a reason, it's probably because you missed a requirement. Availability, for example.

Don't forget to include the external parts, some older regulators are very cheap but operate at lower frequency and/or have low efficiency (eg. MC34063). Some have been cloned or second sourced and are inexpensive for that reason. Others are used in huge volume and are inexpensive compared to "boutique" parts aimed at niche markets.

As far as your followup question about using the same part number in multiple places, that's usually a good thing, however be careful you have allowed enough margin on, say, the input voltage. If your circuit is to be used in an automotive application, your requirements for handling input transients will be quite severe, and protective devices only take you so far.

If you're working with a 12V regulated wall wart, you can probably be okay with an 18V rated device.

\$\endgroup\$
4
  • \$\begingroup\$ Non-automotive project. Supply can be 12-28V DC. I already us TI TPS54231DR to get the 9V output in another project so I am re-using the design. Further research said "using 2 switchers of same freq can amplify the noise/emissions of each other, so consider different freqs to spread the noise across the spectrum." But I'd rather re-use the same part if possible. What is your opinion on this? And one more question, would both regulators use the 12-28V as the input? or can the 3.3V output reg use the 9V as the input (to reduce the size of the 12-28V power plane)? \$\endgroup\$
    – zme
    Commented Sep 12, 2018 at 21:02
  • 1
    \$\begingroup\$ Do you care about noise? You can get beat frequencies that might affect something sensitive at lower frequencies but maybe you've got nothing low level like that. It will likely be more efficient to step both down from the input voltage. The efficiency will vary with input voltage and chip so you have to do the sums, but usually that's true. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Sep 12, 2018 at 21:28
  • \$\begingroup\$ Interesting! The board is simple; ARM MCU @100MHz, 8 relays(9v), 10+ analog inputs (using 8 bit precision), RS485 (3.3Vcc), & Eth PHY. Are those "low level" or "sensitive" to beat freqs? Maybe the analog inputs are? link -- at the end it says to use inductors that have a few ohms of resistance at the switching frequency to stop the beats. If I wanted to avoid beat frequencies entirely, how many KHz of switch freq separation would be required? is 100 or 200KHz enough? \$\endgroup\$
    – zme
    Commented Sep 12, 2018 at 23:19
  • \$\begingroup\$ I better asked my questions here....link \$\endgroup\$
    – zme
    Commented Sep 13, 2018 at 1:55
0
\$\begingroup\$

Unless I had a specific need, I would usually go with the least expensive option I can get easily - usually these parts are inexpensive because they are very common / have been around for a while.

When you need something very specific, like high efficiency, low quiescent current you will tend to pay more as these parts are produced in smaller numbers (eg Linear Tech parts)

The other thing to consider is the cost of the supporting parts (inductors etc) in terms of piece price and design time / real estate - there are parts that offer great design simplicity, but as a cost - eg TI SimpleSwitcher parts

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.