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Being newbie to electronics, I'm unsure which SMD component to choose. I'm trying to build a step down voltage circuit using AMS 1117 (5 v to 3.3 v).

I want to know the SMD capacitor component (bypass caps) that I need to put across voltage regulator (AMS 1117). I know my voltage regulator's component ID : REG1117-3.3.

I think 10uF and 100uF would suffice across AMS 1117 voltage regulator. Can someone please suggest which to use?

EDIT 1: I want to power an ESP 12E using this.

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    \$\begingroup\$ You have a couple of choices here. Use the values suggested by the manufacturer there is usually an application note or section in the data sheet for this type of device. Or learn the principles that drive the value of the capacitors and in the process learn how to determine the capacitor values. Hint: most people look at the datasheet. \$\endgroup\$
    – RoyC
    Commented Oct 8, 2018 at 9:51
  • \$\begingroup\$ @RoyC : I'm trying. It looks like 100uF and 10uF for CAP1206 should suffice. I'm also inclined towards CAP100RP. How to find out the differences or datasheets of the two? \$\endgroup\$
    – Ouroboros
    Commented Oct 8, 2018 at 9:56
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    \$\begingroup\$ I would be wary of using ceramics in this case: the datasheet states "The circuit design used in the AMS1117 series requires the use of an output capacitor as part of the device frequency compensation. The addition of 22μF solid tantalum on the output will ensure stability for all operating conditions". Specifying a tantalum device usually means that there is a minimum output ESR required (older tantalums are in the order of a couple of ohms). Ceramics have ESRs in the order of milliohms at these sizes. \$\endgroup\$
    – Peter Smith
    Commented Oct 8, 2018 at 11:16

2 Answers 2

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The datasheet has no information about load impedance or max capacitive load. I'd just go with what the manufacturer recommends:

enter image description here http://www.ams-semitech.com/attachments/File/AMS1117_20120314.pdf

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It all depend of how much current you gonna draw and how much ripple is acceptable for your application.

Larger is the capacitor, lowest is the ripple, but be careful as some regulators cannot drive large capacitive loads, although 100uF on this particular device should work fine.

The datasheet shows a 22uF capacitor at the ouput on the "typical application" section and usually it's good to follow this.

For SMD components more specifically and the types,

You can use any cap size in SMD as long as the rated voltage and rated capacity suits your need.

Some caps are better at filtering, like Ceramic capacitor will have faster response and longer lifetime than electrolytic. It is quite common, especially in buck conversion, to see a ceramic capacitor before an electrolytic capacitor. The ceramic will take out most of the ripple while the electrolytic will act as bulk cap, this enhance lifetime.

There are different types of ceramic capacitors, like X5R, X7R some of which will be better at filtering due faster response, lower serial resistance.

Although in your case, you probably don't need to worry about it and a simple off the shelve cap will work.

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  • \$\begingroup\$ I understand. I've created circuit where 10uF and 100uF works well. But I did it using non SMD components. I'm thinking of CAP1206, do you think it suits my needs? \$\endgroup\$
    – Ouroboros
    Commented Oct 8, 2018 at 10:00
  • \$\begingroup\$ I edited the answer to add more details. Any size will work as long as you can solder it. \$\endgroup\$
    – Damien
    Commented Oct 8, 2018 at 10:05
  • \$\begingroup\$ in contrast to what Damien states in his answer, you CAN'T just use any size capacitor for a voltage regulator, take a look at this site, especially figure 2. \$\endgroup\$
    – David
    Commented Feb 28, 2020 at 8:16

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