High capacitance from small packages for analog decoupling?

Petter · 19th September 2005, 11:33 AM

I am currently building a project where I have trouble finding room for all the capacitors I require. I am most worried about the analog section where the datasheet suggests I need 10-50uF in places. The vendor's evaluation module uses high quality through-hole Electrolytics, but due to the geometry of my layout I need to use SMD.

High capacitance from small packages is what I need. I have found film devices which offer up to 1uF in SMD1210. However stacking 10 such units is not desirable

so my current plan is to stack say:

1. Silver Mica SMD1210 device
2. two film SMD1210 devices on top
3. one AVC TacMicrochip device on top of that again for the bulk capacitance. http://www.avxcorp.com/docs/catalogs/taclp.pdf

The AVX device seems to offer very high capacitance, low volume, low leakage and reasonable impedances and 15uF in 10V (I operate at 5V analog). What I am not so sure about is the dielectric loss.

In the past, Tantalum capacitors seemed to be shunned by users due to their failure modes (short) and often catastrophic failures. What I have yet to find is a consideration of how well these units perform in audio. These units seem ideal for my needs - your comments on this matter would be greatly appreciated.

Petter

Petter · 20th September 2005, 03:09 PM

From elsewhere someone recommended Panasonic SP (Specialty Polymer). These seem like fine units but are rather large at SMD 7343 (7.3mm by 4.3mm). I have found film devices I could use beneath such units but with limited capacitance of a few uF.

I would still be pleased for other suggestions.

JensRasmussen · 21st September 2005, 11:08 AM

Try the murata GRM32ER60J107ME20

Ceramic, 100uF, 6.3V, X5R, 1210
ESR=1mOhm, ESL=2nH, fres=400Khz

TDK makes a similar devise, but I can not remember the product number.

I hope this helps you

\Jens

JensRasmussen · 21st September 2005, 12:50 PM

More info here:

http://ur-group.co.uk/artesyn/cd/pdf...n_pth12050.pdf

\Jens

Loial · 21st September 2005, 01:35 PM

Why not use SMD electrolytics?

Petter · 23rd September 2005, 02:25 PM

I am using ceramics on the digital side, but am worried about them for the analog side, particularly the low capacitance units.

SMD electrolytics work, but I was looking for something even smaller + they seem harder to handsolder.

Petter

Loial · 23rd September 2005, 05:38 PM

I agree small SMD electrolytics are a real pain in the *** to solder ( and desolder is eaven more tricky... )

I just remembered that I've got a bunch of 6,8 uF 50V ceramic caps ( actually two caps in one ), measuring approx. 5*7*5 mm.
Really easy to solder, I attached an image of it.
Petter - I could send you a few if you'd like, for some coffe-money

5-10 pcs? Where in scandinavia do you live?

By the way... with "small packages" - how small do you mean?

Petter · 25th September 2005, 08:43 AM

How small:

SMD1206 or 1210 would be really good for me but if really large film units can be found, larger is OK. The only problem is that the 1210 units I plan to use are 1uF and the largest "normal" SMD sticks I have seen (in film) have been only a couple of uF thus not really worth the effort as stacking 5 of the small ones is probably just as good as using the big ones + don't cause the same layout issues give that things are getting so tight.

Petter

19th September 2005, 11:33 AM	#1
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	High capacitance from small packages for analog decoupling? I am currently building a project where I have trouble finding room for all the capacitors I require. I am most worried about the analog section where the datasheet suggests I need 10-50uF in places. The vendor's evaluation module uses high quality through-hole Electrolytics, but due to the geometry of my layout I need to use SMD. High capacitance from small packages is what I need. I have found film devices which offer up to 1uF in SMD1210. However stacking 10 such units is not desirable so my current plan is to stack say: 1. Silver Mica SMD1210 device 2. two film SMD1210 devices on top 3. one AVC TacMicrochip device on top of that again for the bulk capacitance. http://www.avxcorp.com/docs/catalogs/taclp.pdf The AVX device seems to offer very high capacitance, low volume, low leakage and reasonable impedances and 15uF in 10V (I operate at 5V analog). What I am not so sure about is the dielectric loss. In the past, Tantalum capacitors seemed to be shunned by users due to their failure modes (short) and often catastrophic failures. What I have yet to find is a consideration of how well these units perform in audio. These units seem ideal for my needs - your comments on this matter would be greatly appreciated. Petter

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20th September 2005, 03:09 PM	#2
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	From elsewhere someone recommended Panasonic SP (Specialty Polymer). These seem like fine units but are rather large at SMD 7343 (7.3mm by 4.3mm). I have found film devices I could use beneath such units but with limited capacitance of a few uF. I would still be pleased for other suggestions.

21st September 2005, 11:08 AM	#3
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	Try the murata GRM32ER60J107ME20 Ceramic, 100uF, 6.3V, X5R, 1210 ESR=1mOhm, ESL=2nH, fres=400Khz TDK makes a similar devise, but I can not remember the product number. I hope this helps you \Jens

21st September 2005, 12:50 PM	#4
JensRasmussen diyAudio Member Join Date: Jul 2002 Location: Denmark - Jutland	More info here: http://ur-group.co.uk/artesyn/cd/pdf...n_pth12050.pdf \Jens

21st September 2005, 01:35 PM	#5
Loial diyAudio Member Join Date: Nov 2004 Location: Gävle	Why not use SMD electrolytics?

23rd September 2005, 02:25 PM	#6
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	I am using ceramics on the digital side, but am worried about them for the analog side, particularly the low capacitance units. SMD electrolytics work, but I was looking for something even smaller + they seem harder to handsolder. Petter

23rd September 2005, 05:38 PM	#7
Loial diyAudio Member Join Date: Nov 2004 Location: Gävle	I agree small SMD electrolytics are a real pain in the *** to solder ( and desolder is eaven more tricky... ) I just remembered that I've got a bunch of 6,8 uF 50V ceramic caps ( actually two caps in one ), measuring approx. 575 mm. Really easy to solder, I attached an image of it. Petter - I could send you a few if you'd like, for some coffe-money 5-10 pcs? Where in scandinavia do you live? By the way... with "small packages" - how small do you mean?

25th September 2005, 08:43 AM	#8
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	How small: SMD1206 or 1210 would be really good for me but if really large film units can be found, larger is OK. The only problem is that the 1210 units I plan to use are 1uF and the largest "normal" SMD sticks I have seen (in film) have been only a couple of uF thus not really worth the effort as stacking 5 of the small ones is probably just as good as using the big ones + don't cause the same layout issues give that things are getting so tight. Petter

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