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5v 1.5A regulator(Mouser # 511-LD29150DT50R) — Parallax Forums

5v 1.5A regulator(Mouser # 511-LD29150DT50R)

hmlittle59hmlittle59 Posts: 404
edited 2009-04-03 20:03 in General Discussion
Hello all,

I was looking at the spec. sheet for STMicroelectronics Part LD29150DT50R and the Application circuit they show has a 0.33 uf on Input and a 10uf on Output. The sheet does not say if its ( electrolytic / ceramic / or Tantalum) and the 10 uf has a polarity indicator. How is one suppose to know what type of parts to order and footprint size(CC1310). I want SMT parts for my design. I know that Wall Warts sometimes are not always the same voltage output even though they may say so.

1) How do I know if it ceramic/tantalum?

2) What determines the foot print size of the CAP?

3) I have 4.7 uf Tantalum on hand will they work in place of the 10 uf for now?

I've seen lots of discussion on the forum about Voltage Regulators but I can't find these answers. Every vendor seems to have different requirements based on their design.

thank to all

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I HAVE LEARN SO MUCH...BUT STILL KNOW SO LITTLE!!!

hmlittle59

Comments

  • LeonLeon Posts: 7,620
    edited 2009-03-31 22:46
    I'd use ceramic chip capacitors on the input and output, as they don't specify the type, and a 10 uF ceramic is cheaper and smaller than a tantalum. I've used ordinary Al electrolytics with similar LDOs. It might be OK with a 4.7 uF on the output, but I'd swap it for the correct value ASAP.

    Leon

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-03-31 22:52
    On this particular part it probably doesn’t matter if you use ceramic, electrolytic or tantalum on the output since the datasheet doesn’t specify. Usually the input capacitor is ceramic. But, in the future if you get a datasheet that does have a recommendation, always follow it. Almost every regulator I use specifies tantalum capacitors on the output for ESR and stability reasons. Often they will list an equivalent Aluminum Electrolytic that can be used instead, and this may have a different value. On many modern LDO regulators the capacitor values and type are somewhat critical for stability. It looks like this part you chose is one of the exceptions. Take care.

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  • hmlittle59hmlittle59 Posts: 404
    edited 2009-03-31 23:19
    Thank for the Quick replies.


    new parts to be ordered

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    I HAVE LEARN SO MUCH...BUT STILL KNOW SO LITTLE!!!

    hmlittle59
  • Carl HayesCarl Hayes Posts: 841
    edited 2009-04-02 01:07
    Tantalum capacitors are electrolytic capacitors, one of several types.· Compared with aluminum electrolytics, tantalum electrolytics:

    (1)· Cost more;

    (2)· Are more reliable;

    (3)· Have less leakage;

    (4)· Are less tolerant of continuous AC flowing through;

    (5)· Have a little greater equivalent series resistance; and

    (6)· Can stand higher temperatures.

    For a filter on a power supply, I'd use an aluminum electrolytic just about always if buying new.

    Electrolytic capacitors have very wide tolerances.· The tolerance ranges for 10 and 4.7 uf electrolytics are not much different; about 90% of either value will fall in the tolerance range of the other value.· Your 4.7 should work just fine, and if the cost of replacing it isn't a problem, I'd use it unhesitatingly.· If buying new ones for this app, I'd order aluminum, but your tantalums are already on hand.· Use'em.

    And, to be kind to an old man, change that I HAVE LEARN SO MUCH to I HAVE LEARNED SO MUCH.· Please?

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    · -- Carl, nn5i@arrl.net

    Post Edited (Carl Hayes) : 4/2/2009 1:17:03 AM GMT
  • Nick McClickNick McClick Posts: 1,003
    edited 2009-04-02 02:21
    Correct me if I'm wrong, but aren't electrolytics less tolerant of cold temps?

    Slightly OT, but what about Ceramic vs. electrolytic for DC-to-AC / Audio out?

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  • Carl HayesCarl Hayes Posts: 841
    edited 2009-04-02 15:15
    Nick McClick said...
    Correct me if I'm wrong, but aren't electrolytics less tolerant of cold temps?

    Slightly OT, but what about Ceramic vs. electrolytic for DC-to-AC / Audio out?

    Less tolerant than what?· And which kind of electrolytics?· And how cold?

    But yes, most ceramic or mica or mylar or polystyrene capacitors, for example, will work better in liquid nitrogen than an aluminum or tantalum electrolytic (or paper) capacitor will.

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    · -- Carl, nn5i@arrl.net
  • Nick McClickNick McClick Posts: 1,003
    edited 2009-04-03 20:03
    found an interesting application guide (pdf).

    The typical temperature range for aluminum electrolytic capacitors is –40 °C to 85 °C or 105 °C. Capacitance varies about +5% –40% over the range with the capacitance loss all at cold temperatures.

    Ceramic capacitors are available in three classes according to dielectric constant and temperature performance. Class 1 (NPO, COG) is suitable for low capacitance, tight tolerance applications in the range of 1 pF to a few mF. Class 2 (X7R) has 20 to 70 times as much capacitance per case size, but capacitance typically varies about ± 10% over its –55 to 125 °C temperature range. The maximum change is +15 % to –25%.

    So yeah, probably not a concern

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