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I'm going to make a PIC programmer, so currently I'm acquiring parts that I'll need. And here's the one part that I can't get:

C2 - 22uF / 16V tantalum or 47uf / 6.3V tantalum
This is a high speed capacitor and should be a tantalum type.

That's what it says in the tutorial.

So my question is: Can I replace this tantalum capacitor with \$22\mu F\$ / higher voltage or \$47\mu F/ 10V\$ or something like this? I'm confused because in tutorial they are using \$47\mu F/6.3V\$ as replacement ...

How do I know how many farads I need ?

Thanks

Adam Lawrence
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xx77aBs
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    The capacitance of a "filter" capacitor is usually fairly non critical. A factor of 2 in value is unlikely to be relevant. Capacitors in some cases can have tolerances of +100% / -50% (wet aluminium electrolytic) but may be +/-5% or 10% or 20% for Tantalum.

    Warning: NEVER use tantalum capacitors in a "high energy" circuit where voltage can EVER exceed the voltage rating of the capacitor. Even the shortest spike (sub microsecond) can puncture the oxide layer and "away it goes". Almost as much fun as a LiIon battery!.

     – Russell McMahon Jul 15 '11 at 14:36
  • Related: http://electronics.stackexchange.com/questions/9120/voltage-rating-and-tantalum-capacitors – Kellenjb Jul 15 '11 at 16:01
  • http://electronics.stackexchange.com/questions/15875/can-capacitors-be-replaced-with-higher-capacitance-ones – Kellenjb Jul 15 '11 at 16:04
  • http://electronics.stackexchange.com/questions/14248/can-i-swap-an-electrolytic-capacitor-with-one-with-a-higher-voltage – Kellenjb Jul 15 '11 at 16:04
  • http://electronics.stackexchange.com/questions/13091/high-voltage-capacitor-in-a-low-voltage-system/13093#13093">13091 – Kellenjb Jul 15 '11 at 16:05

1 Answers1

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I would guess that \$22\mu F\$ is the minimum capacitance that the application can use.

Part characteristics can differ as their voltage rating increases, so be careful not to go 'too' high. (Don't put a 100V capacitor where there once was a 16V part). I would wager that if you can get something between \$22 \mu F\$ and \$47 \mu F\$ in 25V, you'll be fine.

You may also be able to use multilayer ceramic capacitors in parallel to get \$ 22\mu F\$ - just don't use electrolytic. Electrolytic capacitors are not 'high speed' due to their intrinsic parasitic characteristics.

Adam Lawrence
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  • I have good news for you, even 100uF ceramics is not hard to get nowadays :-) So no longer need to parallel. Also, if one use ceramic instead of tantalum, it's generally safe use lower value (like 10uF), but one need to check datasheet. – BarsMonster Jul 15 '11 at 14:46
  • True, but soldering those huge-value ceramic capacitors is a problematic operation. Bad thermal management of the assembly process and board flex can easily break them, leaving you with a non-fusible heat source on your board (usually connected to a power supply rail) which can make a nice fire. Hand-soldering? Forgetaboutit... – Adam Lawrence Jul 15 '11 at 16:21
  • Cannot confirm your bad experience - I handsoldered like 50 of 22 & several 66 uF ceramic caps (1206 case, bigger for 66), and none of them was damaged. I solder at 250C. – BarsMonster Jul 15 '11 at 17:45
  • Consider yourself fortunate. – Adam Lawrence Jul 15 '11 at 18:22
  • Thank you for you answer. I'll look in my local store for capacitor between 22μF and 47μF and the closest to 16V. If I can't find it, I'll use ceramic ones ;) Just one question: are multilayer ceramic capacitors subgroup of ceramic ones, or are all ceramic capacitors multilayer ? – xx77aBs Jul 16 '11 at 12:23
  • MLCC is a blanket term - you need at least three layers (2 conductors and 1 dielectric) to make a capacitor. Higher capacitance values sandwich many of these structures together. – Adam Lawrence Jul 16 '11 at 16:12