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Author Topic: Quick question -- what is this extra device in a 1W white LED package?  (Read 818 times)

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Offline dmacfarland

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Hey guys, I was just looking at this generic 1W white LED and noticed a separate device outside of the white die area (lower right in my photo). After some research, I've seen a similar arrangement in Cree LEDs but no mention of what it is in the datasheets.

All three bonding wires you can see coming from the right are on the same terminal and so are at the same potential. The other terminal is blurred out on the left side.

I'm sure it's something obvious but I can't think of what it would be.
 

Offline Audioguru

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #1 on: January 05, 2017, 02:40:05 AM »
It is the mounting base connection. Maybe to allow you to prevent damage from static electricity.
 

Offline GreggD

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #2 on: January 05, 2017, 03:25:56 AM »
It is a zener diode for ESD.
 
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Offline dmacfarland

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #3 on: January 05, 2017, 03:29:20 AM »
It is a zener diode for ESD.

Thanks, that is what it seemed like to me in my rudimentary testing, but I wasn't sure and didn't want to push it too far.
 

Offline edavid

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #4 on: January 05, 2017, 03:34:22 AM »
It is a zener diode for ESD.

Does that mean these LEDs conduct in the reverse direction?  Or is there also a blocking diode?
 

Offline GreggD

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #5 on: January 05, 2017, 04:51:28 AM »
No blocking diode. Short wavelength leds (blue) are very sensitive to esd. So this zener is across the led, zeners just above the leds normal voltage and clamps at about 0.6v when reverse voltage is applied.
 
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Offline dmacfarland

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Re: Quick question -- what is this extra device in a 1W white LED package?
« Reply #6 on: January 05, 2017, 04:57:58 AM »
No blocking diode. Short wavelength leds (blue) are very sensitive to esd. So this zener is across the led, zeners just above the leds normal voltage and clamps at about 0.6v when reverse voltage is applied.

I was measuring 0.75v, but I was being very ginger with it. In any case, that's pretty much exactly what it looked it :)
 


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