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Murata DC/DC (MEE1S0509DC) hot / frie...

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Chat Zone » Archive through 14 August, 2015 » Murata DC/DC (MEE1S0509DC) hot / fried « Previous Next »

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741
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Username: 741

Post Number: 688
Registered: 08-2005


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Posted on Thursday, 18 June, 2015 - 12:15 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

After some testing (trying to remove noise) I found that sometimes this DC-DC module got very hot.

The output-filter inductor was also hot, but there was no (deliberate) load! However, there must, presumably have been some external route for current to heat the inductor.

I suspected vero-board (burrs etc), then I wondered if the tantalum capacitor had shorted internally. I checked the tracks, replaced the capacitor.

Same thing. Now the DC/DC module has a bulge so is obviously dead.

As a post-mortem, I still cannot see any physical shorts.

It is likely that I may have sometimes, very briefly, shorted the output indavertently.
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cjay
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Username: cjay

Post Number: 221
Registered: 10-2013

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Posted on Thursday, 18 June, 2015 - 03:24 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I wonder if it actually has to have a load, it is after all a switch mode PSU and many of the simpler SMPS do not like being run without a load attached.
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gordon
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Post Number: 1075
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Posted on Thursday, 18 June, 2015 - 03:42 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

The data sheet recommends a minimum load of 10% of the maximum output current. I couldn't see whether the module is output short current protected, but they also recommend a fuse on the input so maybe not. Could have been some sort of short on the output, that caused the failure.

http://power.murata.com/data/power/ncl/kdc_mee1.pdf
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741
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Post Number: 689
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Posted on Thursday, 18 June, 2015 - 04:44 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Yes, I noticed the minimum load requirement, but it only warns Lower than 10% minimum loading will result in an increase in output voltage, which may rise to typically 1.25 times the specified output voltage if the output load falls to less than 5%.

Incidentally, I can only get this from Farnell with £20 min order or Mouser (£12 postage!) or Digikey (twice the unit cost of Farnell).

I need 5V in (for sure) 9 out (perhaps 12), 100mA or more (about 1W if 9V out), low profile. This is the only part I've found under 7.5m high and with a decent data sheet.
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chippie
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Post Number: 352
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Posted on Thursday, 18 June, 2015 - 05:01 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Wow! Must be the size of a house at 7.5m high......
eccentric millionaire financed by 'er indoors
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gordon
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Post Number: 1076
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Posted on Thursday, 18 June, 2015 - 05:12 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

RS have this one that might be suitable. I believe they have no minimum order/free delivery for online orders.

http://uk.rs-online.com/web/p/isolated-dc-dc-converters/6895047/
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741
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Post Number: 690
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Posted on Thursday, 18 June, 2015 - 07:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

"7.5m" Ah, er, yes major typo - or "full-brick" perhaps...

I must admit I don't really understand the difference between the NME0509DC and the MEE1S0509DC, except that I think the latter is a newer design.
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gordon
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Post Number: 1077
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Posted on Thursday, 18 June, 2015 - 07:24 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

There doesn't seem to be a great deal of difference between the devices. They mention a 1 second output short circuit rating for the NME device, so maybe a bit more rugged?
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741
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Post Number: 691
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Posted on Friday, 19 June, 2015 - 10:15 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

That's interesting, thanks for pointing it out.
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cjay
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Post Number: 222
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Posted on Friday, 19 June, 2015 - 11:28 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

NMx devices were Newport, Murata appear to have taken them over.

Do you definitely need the isolation or just the voltage?
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741
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Post Number: 692
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Posted on Monday, 22 June, 2015 - 11:21 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I need the isolation.

Incidentally, the most recent NME datasheet has deleted all reference to short-circuit tolerance.

(Even the old DS said Short-circuit protection 1 second...Supply voltage must be disconnected at the end of the short circuit duration). So it isn't very tolerant.

Looks like Murata found problems even at that?

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