Re: Wrong packaged diode

On Sun, 7 Feb 2010 03:17:45 -0800 (PST), djj08230 <(E-Mail Removed)>
wrote:

>Hello all,
>
>A board we produce has a battery that power a static RAM through a
>diode. This is a SMD package, maybe a SMA, but can't say for sure
>right now.
>
>We have had a few problems with the battery circuit, that I know have
>been solved changing the diode.
>
>I have seen only one of those myself, and it looks like the diode is
>packaged the other way round i.e. the package strip pointing to the
>anode instead of pointing to the cathode.
>
>Is this at all possible ? Am I doing something wrong ? Any similar
>experiences around ?
>As the board is produced in China, I would tend to think it is a
>counterfeit diode.
>
>Thank you in advance.
>
>Josep

More info needed. Many diodw packages can be obtained with alternate
pin-out or polarity, at a premium.

Some diodes have functional characteristics in the forward and reverse
direction, which might require their use in what looks like an
inverted mode.

RL

On Sun, 7 Feb 2010 23:36:33 -0800 (PST), djj08230 <(E-Mail Removed)>
wrote:

>On Feb 7, 9:48*pm, legg <l...@nospam.magma.ca> wrote:
>> On Sun, 7 Feb 2010 03:17:45 -0800 (PST), djj08230 <djj08...@gmail.com>
>> wrote:
>>
>>
>>
>>
>>
>> >Hello all,
>>
>> >A board we produce has a battery that power a static RAM through a
>> >diode. This is a SMD package, maybe a SMA, but can't say for sure
>> >right now.
>>
>> >We have had a few problems with the battery circuit, that I know have
>> >been solved changing the diode.
>>
>> >I have seen only one of those myself, and it looks like the diode is
>> >packaged the other way round i.e. the package strip pointing to the
>> >anode instead of pointing to the cathode.
>>
>> >Is this at all possible ? Am I doing something wrong ? Any similar
>> >experiences around ?
>> >As the board is produced in China, I would tend to think it is a
>> >counterfeit diode.
>>
>> >Thank you in advance.
>>
>> >Josep
>>
>> More info needed. Many diodw packages can be obtained with alternate
>> pin-out or polarity, at a premium.
>>
>> Some diodes have functional characteristics in the forward and reverse
>> direction, which might require their use in what looks like an
>> inverted mode.
>>
>> RL- Hide quoted text -
>>
>> - Show quoted text -
>
>Thank you.
>I've got the info now.(monday morning here)
>
>The diode is MURS105T3G from On Semiconductors in an SMB package.
>http://www.onsemi.com/pub_link/Colla...URS120T3-D.PDF
>
>Probably not the best bit, but to me, this is an odd behaviour.
>Testing the diode with a multimeter looks like the package is
>reversed. Do they hand-assembly these tiny diodes ? (!!!)
>
>
>Josep

There is no point in producing an 'axial' two-lead device with an
alternate pin-out. Alternate pinouts only occur if a mechanical
reversal is impractical or impossible to achieve as shipped.

Check part out-of-circuit. Forward voltage drop will be evident if
positive conventional current is forced into anode to return via
cathode. If cathode band (schematic symbol points to it) is
incorrectly impressed, you've got a load of rubbish.

RL