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Locking problem in dsPIC33EV256GM104 processor.

 
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MCUprogrammer



Joined: 08 Sep 2020
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Locking problem in dsPIC33EV256GM104 processor.
PostPosted: Tue Jan 24, 2023 2:21 am     Reply with quote

Hi
Processor hangs due to noise. I put a 100nf capacitor on the VDD VSS pins. I put 100nf on the AVDD-AVSS pin. I put a tantalum 10uf capacitor on the VCAP pin. ICSP socket line length approx. 80mm with MCLR line. I threw a 10uf tantalum cap on this line. What are your suggestions?

I solder the processor to the adapter in the link.
https://robiz.net/05mmtqfp2

By the way, I put 1uf instead of 100nf on the supply voltage lines. It still didn't help.
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Ttelmah



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PostPosted: Tue Jan 24, 2023 2:58 am     Reply with quote

Understand that on capacitors, size is not necessarily better.
A 0.1uF ceramic capacitor, has better performance at frequencies over
1MHz, than a 100uF electrolytic. It is vital to be using the right
type of capacitor.
You talk about putting 'a' "100nf capacitor on the VDD VSS pins". Your
chip has three pairs of VDD and VSS pins. All need to be connected to
power, and each pair needs a 100nF capacitor close to them. Preferably
a ceramic. Now, unfortunately, your 'adapter' introduces significant
lead lengths to the capacitors. I normally try to get the capacitors within
5mm of the actual pins.
I've often suggested that people thinking about suppression, have a look
at something like a PC motherboard. If you look over these, you have
dozens of large capacitors around the actual supply connections, but then
right across the board, every few mm, there are small ceramic capacitors.
Usually several immediately around the processor, and then another
every couple of IC's across the board. Once you understand that
manufacturers do not waste money, you start to realise how essential
these are. These boards are also multi layer, with the ground being it's
own layer right across the board.
Probably the 'best' capacitor is polypropylene, but these are very
bulky. For high frequency blocking, ceramic is the best, and are small
for reasonable sizes. On polarized capacitors, polymer, then tantalum,
then aluminium. Tantalum capacitors can be considered slightly
dangerous, but the 'military' rated versions with solid electrolytes
are designed to avoid these problems, but are expensive. On ceramic,
the paraelectric versions (class 1), are 'better', but have lower permittivity
so are larger.
Choosing capacitors is a lot more complex than just choosing a 'value',
there are multiple parameters involved, and placement is often the most
important parameter.

I have deliberately ignored a lot of the more complex types, like vacuum
capacitors. You are unlikely to meet things like this.
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