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Author Topic: What is the point of a 3 legged tantalum capacitor?  (Read 5483 times)

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Offline alank2Topic starter

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What is the point of a 3 legged tantalum capacitor?
« on: July 07, 2018, 07:54:07 pm »
Like this:

http://www.vishay.com/docs/40044/299d.pdf

Why 3 legs if they are just shorted together internally?

To ensure proper polarization?
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Offline Gyro

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #1 on: July 07, 2018, 07:56:46 pm »
It prevents the danger of reversed insertion, yes.
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Online ahbushnell

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #2 on: July 07, 2018, 08:03:26 pm »
Quote from: alank2 on July 07, 2018, 07:54:07 pm
Like this:

http://www.vishay.com/docs/40044/299d.pdf

Why 3 legs if they are just shorted together internally?

To ensure proper polarization?
It says for reverse installation on the data sheet.

Sent from my SM-G930V using Tapatalk

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Offline alank2Topic starter

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #3 on: July 07, 2018, 09:04:31 pm »
Thanks guys!
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Offline texaspyro

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #4 on: July 08, 2018, 04:04:57 am »
My company used to supply boards to IBM and they required all tants to be 3-leg.
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Offline JS

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #5 on: July 08, 2018, 04:50:50 am »
Would the symmetrical design also reduce the series inductance, given a proper layout implementation?

JS
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Offline German_EE

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #6 on: July 08, 2018, 08:29:04 am »
1) Lower impedance connections to ground

2) Impossible (I hope) to insert the wrong way in a PCB

3) Mechanically more stable, no need to use any of the white goo
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Offline David_AVD

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #7 on: July 08, 2018, 10:38:39 am »
In a similar vein, I noticed some 9 pin SIL dual op-amps just last week.  They are the same as the 8 pin SIL version, but with an extra V+ pin at the pin 1 end.  This makes them symmetrical.
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Offline b_force

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #8 on: July 08, 2018, 01:34:51 pm »
There are similar constructions for certain ceramic capacitors as well.
Mostly to get the best ESR for high frequencies.
They aren't cheap though
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Offline precaud

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #9 on: July 08, 2018, 04:53:06 pm »
Quote from: alank2 on July 07, 2018, 07:54:07 pm
Why 3 legs if they are just shorted together internally?
To ensure proper polarization?

They're designed to stop you from being able to insert them into your LCR meter's radial component fixture.    ;D
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Offline alank2Topic starter

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #10 on: July 08, 2018, 07:38:10 pm »
Quote from: precaud on July 08, 2018, 04:53:06 pm
They're designed to stop you from being able to insert them into your LCR meter's radial component fixture.    ;D

Probably so you have to buy the special 3 legged capacitor LCR version!
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Offline station240

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #11 on: July 08, 2018, 08:40:19 pm »
Quote from: precaud on July 08, 2018, 04:53:06 pm
Quote from: alank2 on July 07, 2018, 07:54:07 pm
Why 3 legs if they are just shorted together internally?
To ensure proper polarization?

They're designed to stop you from being able to insert them into your LCR meter's radial component fixture.    ;D

My ESR meter has a set of leads with alligator clips on one end, and PCB pins on the other. How else do you measure huge inductors.
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Offline CopperCone

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #12 on: July 08, 2018, 10:19:03 pm »
you can save on drug testing your manufacturing personnel
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Offline SpencerTC

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Re: What is the point of a 3 legged tantalum capacitor?
« Reply #13 on: July 10, 2018, 12:45:51 pm »
Quote from: alank2 on July 08, 2018, 07:38:10 pm
Quote from: precaud on July 08, 2018, 04:53:06 pm
They're designed to stop you from being able to insert them into your LCR meter's radial component fixture.    ;D

Probably so you have to buy the special 3 legged capacitor LCR version!
At my company we are currently dealing with the "you have to buy our special test fixture" syndrome. So this gave me a nice laugh.
Thanks.
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