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circuit
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Joined: 10/01/2016
Location: United Kingdom
Posts: 290

Posted: 02:23pm 16 Nov 2018

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Having now been totally successful with the 28 and 44 pin Micromites; 100 pin Micromite Plus, Armite H7 and with the latest Armite L4 on the bench, I have started constructing the Micromite Extreme and reached a problem; the crystal oscillator.

The Micromite eXtreme manual recommends an Epson SG8002DCPHB24MHz but I cannot locate this part. Can anyone point me to a suitable oscillator (preferably on the UK-RS website or Farnell) for this purpose?

I also note that the Epson SG8002DCPHB24MHz appears to be a 5 volt device. How is this reconciled with the PIC32MZ2048EFH144-250I/PL 3.3 volt chip?

I have used crystals+capacitors on many chips in the past but these crystal oscillators are confusing me somewhat. I gather that there are two pins on one side which I presume just connect to Vdd/Vss and of the other two, one is the OSC output and the other goes to ground. Do I need to feed 5V into the oscillator for a 3.3v chip?

Pointers in the right direction would be most appreciated.

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10572

Posted: 02:39pm 16 Nov 2018

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On the MMX144 backpack I either use a 5V oscillator fed with 5V and with a potential divider on the output or a 3.3V part. The PCB has pads for both. The problem is that there aren't any DIP 3.3V versions. However, a 7x5mm 3.3V oscillator of which there are many will fit on a SOIC-DIP adapter. Leave the output select pin unconnected.Edited by matherp 2018-11-18

circuit
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Joined: 10/01/2016
Location: United Kingdom
Posts: 290

Posted: 07:03pm 16 Nov 2018

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matherp said On the MMX144 backpack I either use a 5V oscillator fed with 5V and with a potential divider on the output or a 3.3V part. The PCB has pads for both. The problem is that there aren't any DIP 3.3V versions. However, a 7x5mm 3.3V oscillator of which there are many will fit on a SOIC-DIP adapter. Leave the output select pin unconnected.

Thank you, Peter, for your most rapid and helpful reply. I have not used these components before, so could you indicate if the following are suitable;
If I take the DIP route and go for 5V and a potential divider then I could use;
https://uk.rs-online.com/web/p/crystal-oscillators/4785783/

If I go for the 3.3 volt part then this would be suitable;
https://uk.rs-online.com/web/p/crystal-oscillators/4788760/
- it seems to be 7x5mm and therefore would mount on a SOIC-DIP as you propose.

Sorry to be a pain, but I am on quite a roll with successfully hand-soldering 44, 64 and 100 pin chips and as I move to your 144 pin Micromite eXtreme I do not want to mess up with this key component.

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10572

Posted: 07:31pm 16 Nov 2018

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Either of those should be fine, 3.3V version probably preferred.

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