Difference between microcontrollers

ortegahernandes · Joined: 14 Feb 2020 Posts: 23

My question is not about programming.

What is the difference between automotive and industrial microcontrollers?

The question is to see if it is possible to replace a 24FV32KA304 PIC with a 24FJ256GA704.

The operation that this microcontroller does is a little critical, but at normal temperatures.

The replacement is due to the amount of RAM.

Sorry for the bad english, I'm using a translator.....

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

They give the reasons why a PIC is "recommended for automotive design" on this page:
https://www.microchip.com/design-centers/automotive-solutions/recommendations-for-automotive-designs

Also see this:
https://www.eevblog.com/forum/microcontrollers/can-i-use-industrial-grade-microcontroller-in-automotive-product/

Data sheets:

24F32KA304:
http://ww1.microchip.com/downloads/en/DeviceDoc/30009995e.pdf

2FJ256GA704/5:
http://ww1.microchip.com/downloads/en/DeviceDoc/PIC24FJ256GA705-Family-Data-Sheet-DS30010118D.pdf

Webpages for each PIC:
https://www.microchip.com/wwwproducts/en/PIC24FJ256GA704#additional-features

https://www.microchip.com/wwwproducts/en/en552758#additional-features

Ttelmah · Joined: 11 Mar 2010 Posts: 19505

Generally the first key difference is temperature rating.
The standard ratings in order are:
Commercial
Industrial
Automotive
Military

You can always use military rated parts for all four classes.
The ratings have changed at various times, but currently are:
Commercial 0C to 70C
Industrial -40C to 80C (this used to be only -25C to 80C).
Automotive -40C to 125C
Military -55C to 125C

Beware of just how hot things can get in a car. If you park a car in the
sun, bits inside can quite quickly get too hot to touch.
Separately, things like voltage regulators listed as 'automotive' are designed
to cope with the particular types of spike noise in this environment.

Though this PIC is rated 'industrial', it has the temperature rating required
for 'automotive'. This is obviously a decision by MicroChip to make
the products suitable for a wider market.

However, the key thing to look for is the words 'functional safety ready' in
the product paperwork. These are chips that meet the ISO26262
certification for automotive applications.
If you go to the parametric page, and select 'all products', and 'automotive
recommended'. :

<https://www.microchip.com/ParamChartSearch/chart.aspx?branchID=8181>

You will see that in general ones with much larger ROM sizes are not listed.
This is because as the ROM size grows it becomes increasingly difficult
to ensure reliability. The KA304, is the largest chip in the XLP range
meeting this requirement. If you need more RAM and ROM, you should
be looking at a chip like the PIC24FJ64GA004, which is at the bottom of
this list.

Now these are chips certified as usable in systems requiring safety.
Really you need to be using chips from this range.

However there are a lot more larger chips in the PIC33 family certified
like this:
<https://www.microchip.com/design-centers/16-bit/functional-safety>

Chips like the PIC33EP128GS704 for example might give you both
extra size and performance, and the safety certification.

The 24FJ256GA704 is not recommended in this way. It is your decision....

ortegahernandes · Joined: 14 Feb 2020 Posts: 23

Ttelmah ....................................

Thank you very much for the beautiful explanation.

The operating temperature will be 10 to 40 degrees, as it is an equipment that will be in the user's hand. So there’s no problem with the temperature.

The product already exists and the choice of 24F32KA304 was due to the low consumption as it is powered by batteries. But sometimes it needs to make a special dedication and it is necessary to reprogram it. That's why I had talked about the 24FJ256GA704, because it would serve pin to pin. The difference would be a More VSS.

However, you showed me one that will fit the PIC24FJ64GA004 much better. It will be much better than the 24FJ256GA704.

Again, very grateful for the explanation and the tip from PIC24FJ64GA004.

temtronic · Posted: Sat Feb 15, 2020 7:23 am

Since it's a battery powered device, consider a different battery. It's amazing the capacity some cells have today, though you need to read the spec sheets.
Also, read the PICs datasheet, application notes, etc. to see about power saving methods. It may be possible to save 5-10-25% of the power. Something as simple as getting rid of floating point math will save power. Changing pullups from 10K to 1M may also help. Use very low current LEDs. There's lots of ways to save a little here, a little there. It all helps !

ortegahernandes · Joined: 14 Feb 2020 Posts: 23

temtronic ..........................

Thank you for the tips.

The microcontroller that "Ttelmah" indicated (PIC24FJ64GA004), despite not being low power, his consumption is within what I need, in fact, even with a lot of slack.

according to data sheet, 650uA / MiPS

(Operating current: 650 uA / MIPS, typical at 2.0V)

I will use about 8 MIPS (16 MHz) which "theoretically" would give 5.2mA outside the peripherals.

The use of the microcontroller is not going to happen all the time, and two 2500mAh batteries are used, so in terms of consumption it is fine.

The PIC24FJ64GA004 will only be used when you need more RAM, otherwise we will continue with the 24F32KA304.

Grateful for the attention.

Hug.