Ceramic capacitors for higher voltage switchers

Joerg
Guest

Sat Mar 06, 2010 1:18 am

Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything

Quote:

0.47uF/>100V in thru-hole seems outlandishly pricey.

--
Regards, Joerg

http://www.analogconsultants.com/

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Tim Williams
Guest

Sat Mar 06, 2010 7:58 am

"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...

Quote:

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

Well, take a guess at power dissipation and find the damping factor (X7R is
what, 1.5% or something?). If you're running hot, low power is probably a
good idea, like 1/8W or something. And use lots of copper (ha, like you
ever have the space).

Quote:

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive.

So stack them horizontally instead? :-)

Or if you're cramped for horizontal space, maybe you could make a capacitor
daughterboard so they're stacked horizontally, on a vertical board...

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Robert Baer
Guest

Sat Mar 06, 2010 10:55 am

Tim Williams wrote:

Quote:

"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...
Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

Well, take a guess at power dissipation and find the damping factor (X7R is
what, 1.5% or something?). If you're running hot, low power is probably a
good idea, like 1/8W or something. And use lots of copper (ha, like you
ever have the space).

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive.

So stack them horizontally instead? :-)

Or if you're cramped for horizontal space, maybe you could make a capacitor
daughterboard so they're stacked horizontally, on a vertical board...

Tim

Just solder the caps in so they are on edge (vertical); one may be

able to use 4 in parallel this way and use the same PCB board space.

Joerg
Guest

Sat Mar 06, 2010 4:04 pm

Tim Williams wrote:

Quote:

"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...
Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

Well, take a guess at power dissipation and find the damping factor (X7R is
what, 1.5% or something?). If you're running hot, low power is probably a
good idea, like 1/8W or something. And use lots of copper (ha, like you
ever have the space).

I wish they were physically a tad larger.

Quote:

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive.

So stack them horizontally instead? :-)

Or if you're cramped for horizontal space, maybe you could make a capacitor
daughterboard so they're stacked horizontally, on a vertical board...

The client won't like that :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg
Guest

Sat Mar 06, 2010 4:04 pm

Robert Baer wrote:

Quote:

Tim Williams wrote:
"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...
Anyone know what sort of ripple the FK22 series from TDK can take,
say a 0.47uF/250V? I need some ceramics as output caps of a SEPIC
that is variable up to almost 100V, with some gusto (>50 watts).
Can't use electrolytics because of a harsh environment.

Well, take a guess at power dissipation and find the damping factor
(X7R is what, 1.5% or something?). If you're running hot, low power
is probably a good idea, like 1/8W or something. And use lots of
copper (ha, like you ever have the space).

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive.

So stack them horizontally instead? :-)

Or if you're cramped for horizontal space, maybe you could make a
capacitor daughterboard so they're stacked horizontally, on a vertical
board...

Tim

Just solder the caps in so they are on edge (vertical); one may be
able to use 4 in parallel this way and use the same PCB board space.

Can't do that, it must remain machine-solderable.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Archimedes' Lever
Guest

Sat Mar 06, 2010 8:30 pm

On Sat, 06 Mar 2010 01:55:35 -0800, Robert Baer <robertbaer_at_localnet.com>
wrote:

Quote:

Can't use
electrolytics because of a harsh environment.

Use hermetically sealed military versions then.

The difference in performance is worth the difference in price.

Archimedes' Lever
Guest

Sat Mar 06, 2010 8:34 pm

On Sat, 06 Mar 2010 01:55:35 -0800, Robert Baer <robertbaer_at_localnet.com>
wrote:

Quote:

Just solder the caps in so they are on edge (vertical); one may be
able to use 4 in parallel this way and use the same PCB board space.

Pretty much very labor intensive assembly work. Not very good for any
automated process, so not good for anything that has intentions of large
volume production.

For short run, hand assembly though, no problem.

Vertical daughter cards are the way we did it in the HV lab.

50 Watts is a lot of loading for a ceramic cap bank to manage the
ripple of.

Joerg
Guest

Sat Mar 06, 2010 8:45 pm

Archimedes' Lever wrote:

Quote:

On Sat, 06 Mar 2010 01:55:35 -0800, Robert Baer <robertbaer_at_localnet.com
wrote:

Can't use
electrolytics because of a harsh environment.

Use hermetically sealed military versions then.

The difference in performance is worth the difference in price.

I know, and I do that. But it's often not easy to find some for higher
voltages with low enough ESR _and_ being available without huge leadtimes.

--
Regards, Joerg

http://www.analogconsultants.com/

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Use another domain or send PM.

mook johnson
Guest

Sun Mar 07, 2010 12:03 am

"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...

Quote:

Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything
0.47uF/>100V in thru-hole seems outlandishly pricey.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Haven't used these particular caps but I have run some X7R 250V surfamce
mount 2220 caps at 1A p-p ripple current at 10Khz. No
noticable heating at all.

A also run a 500V 2225 .47uF caps on the output of a 150V rail that can put
out 75W (300Khz ripple) with no noticable heating.

You really have to hog some current on the ceramics to heat them up.

That said I did have some x7r .1uF cap with teh yellow epoxy turn red when a
5A audio amp IC started oscillating into it. It was in an RC damper on the
output. Scratched my head for a while trying to figure out why that cap
got hot. I had thought before that ceramic caps were nearly ideal. Smile

Joerg
Guest

Sun Mar 07, 2010 12:38 am

mook johnson wrote:

Quote:

"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...
Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything
0.47uF/>100V in thru-hole seems outlandishly pricey.
--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Haven't used these particular caps but I have run some X7R 250V surfamce
mount 2220 caps at 1A p-p ripple current at 10Khz. No
noticable heating at all.

A also run a 500V 2225 .47uF caps on the output of a 150V rail that can put
out 75W (300Khz ripple) with no noticable heating.

I can't use these large SMT sizes in this case because of thermal stress
issues, cracks, and all that.

Quote:

You really have to hog some current on the ceramics to heat them up.

That said I did have some x7r .1uF cap with teh yellow epoxy turn red when a
5A audio amp IC started oscillating into it. It was in an RC damper on the
output. Scratched my head for a while trying to figure out why that cap
got hot. I had thought before that ceramic caps were nearly ideal. :)

That's one reason why I asked. I've managed to turn capacitor ceramic
into bubbly green glass. But that was several MHz and several amps
through just one. The usual, had only one, did a quick experiment, "Come
on, hang on another 10 secs" ... *PHOOMP*

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg
Guest

Sun Mar 07, 2010 1:51 am

miso_at_sushi.com wrote:

Quote:

On Mar 5, 4:18 pm, Joerg <inva...@invalid.invalid> wrote:
Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything
0.47uF/>100V in thru-hole seems outlandishly pricey.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Rock | Joerg | Hard Place
Wink

The designs that get chucked over onto my desk are nearly always like
that :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

miso@sushi.com
Guest

Sun Mar 07, 2010 2:03 am

On Mar 5, 4:18 pm, Joerg <inva...@invalid.invalid> wrote:

Quote:

Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything
>0.47uF/>100V in thru-hole seems outlandishly pricey.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Rock | Joerg | Hard Place
Wink

Michael A. Terrell
Guest

Sun Mar 07, 2010 4:33 am

Joerg wrote:

Quote:

That's one reason why I asked. I've managed to turn capacitor ceramic
into bubbly green glass. But that was several MHz and several amps
through just one. The usual, had only one, did a quick experiment, "Come
on, hang on another 10 secs" ... *PHOOMP*

You have been reported to the 'Society For The Prevention Of Cruelty
To Components'.

--
Greed is the root of all eBay.

legg
Guest

Sun Mar 07, 2010 6:08 am

On Fri, 05 Mar 2010 16:18:52 -0800, Joerg <invalid_at_invalid.invalid>
wrote:

Quote:

Gents,

Anyone know what sort of ripple the FK22 series from TDK can take, say a
0.47uF/250V? I need some ceramics as output caps of a SEPIC that is
variable up to almost 100V, with some gusto (>50 watts). Can't use
electrolytics because of a harsh environment.

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive. Anything
0.47uF/>100V in thru-hole seems outlandishly pricey.

You can get capacitor characteristics from TDK.

http://www.tdk.co.jp/ccv/index.asp

The resistance, reactance and voltage/temperature dependencies are
illustrated graphically.

A 0.1uF 100V X7R part in 1206/3216 body size, 3216X7R2A104M, exhibits
an internal series resistance of 30mOhms, over the range of common
power conversion frequencies.

RL

Robert Baer
Guest

Sun Mar 07, 2010 10:21 am

Joerg wrote:

Quote:

Robert Baer wrote:
Tim Williams wrote:
"Joerg" <invalid_at_invalid.invalid> wrote in message
news:7vdlbmFeo1U1_at_mid.individual.net...
Anyone know what sort of ripple the FK22 series from TDK can take,
say a 0.47uF/250V? I need some ceramics as output caps of a SEPIC
that is variable up to almost 100V, with some gusto (>50 watts).
Can't use electrolytics because of a harsh environment.

Well, take a guess at power dissipation and find the damping factor
(X7R is what, 1.5% or something?). If you're running hot, low power
is probably a good idea, like 1/8W or something. And use lots of
copper (ha, like you ever have the space).

http://www.tdk.co.jp/tefe02/e4942_fk.pdf

Stacked SMTs are great but boutiquish and expensive.

So stack them horizontally instead? :-)

Or if you're cramped for horizontal space, maybe you could make a
capacitor daughterboard so they're stacked horizontally, on a
vertical board...

Tim

Just solder the caps in so they are on edge (vertical); one may be
able to use 4 in parallel this way and use the same PCB board space.

Can't do that, it must remain machine-solderable.

I bet pick-and-place can do it..by using a small dot of adhesive to

hold a cap that is placed, another dot nearby for nest cap, etc (all
dots could be placed first and then the caps).
Solder paste mask can be same as if one cap laid down in conventional
form.
"Never" say "never".