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Helpful ReplyHot!PIC32MM QFN36 Exposed Pad

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Cosme_Fulanito
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2018/04/04 23:15:56 (permalink)
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PIC32MM QFN36 Exposed Pad

Hello there,
 
I'm making a board with the PIC32MM0064GPM036-I/M2, this is a QFN36 package with exposed pad. I can't find any reference on the datasheet to the connection of the exposed pad. The obvious solution is to connect it to ground. But I just find it odd that it's not specified. So I guess the question is; should I connect it to GND or leave it floating?
 
Regads,
Daniel
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Jim Nickerson
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 06:11:59 (permalink) ☄ Helpfulby bblessing 2018/04/05 08:53:02
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I wonder if your ohm meter might be used to determine if the exposed pad is connected to a ground pin ?
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Cosme_Fulanito
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 08:45:07 (permalink)
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That's a good idea, sadly I don't have samples of the device at hand. I'm further puzzled by the lack of replies. Is it too dumb of a question so people ignore it, or is it really so mysterious if the EP is connected to ground or not?
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Jim Nickerson
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 08:47:03 (permalink)
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Maybe you could ask Microchip Support
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Jim Nickerson
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 08:51:31 (permalink) ☄ Helpfulby Cosme_Fulanito 2018/04/05 09:20:54
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bblessing
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 08:54:26 (permalink) ☄ Helpfulby Cosme_Fulanito 2018/04/05 09:20:49
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JANickerson
I wonder if your ohm meter might be used to determine if the exposed pad is connected to a ground pin ?


I found the same problem with the PIC32MZ2064DAG176 chip, and the suggestion was to ohm it out. It turns out the exposed pad is connected to GND. Thus, get the free samples and follow Jim's advice.
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timijk
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 08:56:23 (permalink)
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AN2089 Package Application Note for QFN and DFN Package
 
http://ww1.microchip.com/...appnotes/00002089a.pdf
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Cosme_Fulanito
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 09:20:30 (permalink)
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Thanks for the replies. From what I gather here and the linked articles, it seems the pad is not electrically connect to the die but can be connected to GND for heat dissipation. I will do that. 
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Jim Nickerson
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 09:22:46 (permalink)
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I would suggest contacting Microchip Support / FAE for a definitive answer
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Cosme_Fulanito
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Re: PIC32MM QFN36 Exposed Pad 2018/04/05 09:29:25 (permalink)
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JANickerson
I would suggest contacting Microchip Support / FAE for a definitive answer


You are right, I will do that. I just think that it would be quite terrible if the EP was electrically connected and they didn't state it in the datasheet. But it's just an assumption. Like when I thought crystal oscillators worked in the PIC32MZ line, silly me. 
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Cosme_Fulanito
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Re: PIC32MM QFN36 Exposed Pad 2018/04/13 06:12:42 (permalink) ☄ Helpfulby Jim Nickerson 2018/04/13 06:17:15
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Hello again, I got a reply from Microchip's support so I'm posting it here for future readers.
 
Hello there, 

I'm making a board with the PIC32MM0064GPM036-I/M2, this is a QFN36 package with exposed pad. I can't find any reference on the datasheet to the connection of the exposed pad. Should the EP be left floating, can I connect it to ground, or must I connect it to ground? Regards
 
Hi Daniel,

You can connect the exposed pad to the ground or leave it floating unless otherwise specified in the datasheet. 
The exposed pad in QFN packages is used to increase maximum power dissipation of the packages. 
In most applications, the exposed pad is connected to ground.

Warm Regards, Andres
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acharnley
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Re: PIC32MM QFN36 Exposed Pad 2019/11/22 05:20:05 (permalink) ☄ Helpfulby Jim Nickerson 2019/11/22 07:23:00
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Just to revisit this, I had the same response from Microchip regarding the 64 pin version of this chip where they somewhat cryptically said the pad is floating internally so can be connected to ground but connecting to Vdd will destroy the device.  

Originally I made prototype with the pad grounded and consistently had a 3.4 ohm short between Vdd/Vss. Therefore the actual answer is no, the pad MUST be floating because it is connected to something internally and it's not ground (at least on the 64 pin version).
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