topic Re: MC9S12DG128 Cold start-up problem in S12 / MagniV Microcontrollers

MC9S12DG128

LAR — Mon, 11 Dec 2006 22:55:08 GMT

Hi,

I use to use the MC9S12DG128BCPV on a board that must operate at -32C, which it did, no problem.

Now that the leaded BCPV is no longer available, I have switched to the Pb free CPVE version. My first two boards now both fail at -32C and it appears that the micro is not running.

I still have more tests to do to confirm this, but are there any known issues with the Pb free CPVE version at extreme cold temperatures? It's operating spec is -40C.

Thanks for any help.

Re: MC9S12DG128

Alban — Tue, 12 Dec 2006 05:52:34 GMT

Hello,

Every single device is being tested before leaving the factory.

That's why I'm wondering if you changed anything else in the production flow ?

- Comformance coating,

- humidity,

- oscillator components,

- PCB

- solder material,

- soldering temperature ...

Alban.

Re: MC9S12DG128 Cold start-up problem

LAR — Tue, 12 Dec 2006 16:24:17 GMT

Hi,

Thanks for the reply.

Nothing has changed and we have been building these boards for the last two years. We've fitted the new Pb free part to an old board and that is now the same.

The lowest temp that is powers up ok is -17C. Below this temp, you have switch on, then off, then back on again for the micro to run.

Today, I will be monitoring clocks, etc and de-bugging the code.

Thanks.

Re: MC9S12DG128 Cold start-up problem

LAR — Tue, 12 Dec 2006 19:00:55 GMT

Does anyone know why the 'B' was dropped from the MC9S12DG128B part number?

Re: MC9S12DG128 Cold start-up problem

Alban — Tue, 12 Dec 2006 21:21:27 GMT

Hi LAR,

This is a new question that could be a new thread. Being lazy today, I'll leave it here

The B is linked to the Flash Generation.

B parts were improved in term of endurance and retention and the B was dropped.

B = older Flash.
no B = newer Flash

I would not recommend the use of B parts for new Designs.

Cheers,

Alban.

Re: MC9S12DG128 Cold start-up problem

Alban — Tue, 12 Dec 2006 21:30:46 GMT

Interesting info: switch off and on again...

It sounds like a vulgar IT Technical Support Helpline where you support them

I thought that Lead Free was requiring a different soldering temperature, because of the absence of lead.

Are my thoughts wrong ?

Have you tried parts from a different batch (code below MCU part number) ?

May be something is wrong with your batch, but I doubt it as the device is used quite widely and I have to say I would have heard from it...

So let's investigate the Application:

It seems the failure can easily be repeated, that is great.

When you lose the MCU, it would be interesting to follow the RESET, VDDs, and CLOCK lines.

May be when the board is getting cold, the power supply characteristics affect the MCU.

Do you have schematics (or part of it) you could disclose ?

Same for the PCB layout ?

So we can check the MCU environment.

If you've got any objection or other element, feel free to express !

Same for other Community Members, feel welcome to share your experience !!!

Cheers,

Alban,

Re: MC9S12DG128 Cold start-up problem

LAR — Tue, 12 Dec 2006 23:57:07 GMT

Oops, sorry.

Thanks for info about the B.

Does that mean for new designs (and older existing designs), we would need to amend the code to write to the newer flash?

Appologies, but I am a hardware engineer, not a software engineer. Is the flash written to during normal operation or is it where the programming code is stored?

Why do you not recommend the B for new designs?

We have found that the B version is the only version that works.

Thanks,

LAR

Re: MC9S12DG128 Cold start-up problem

Alban — Wed, 13 Dec 2006 00:12:02 GMT

Hello LAR,

As far as I know, there is no change for the user.

No code to update at all, nor hardware.

The Flash can be programmed in both cases. For instance, if the software wants to keep some data even during a loss of power, it will store it in Flash. Same for logging data.

I don't recommend the 'B' because the 'without-B' is better. The 'B' does work though.

Are you saying the temperature problem only occurs with Non-B versions ?

Cheers,

Alban.

Re: MC9S12DG128 Cold start-up problem

LAR — Wed, 13 Dec 2006 00:16:20 GMT

Hi,

Pb free components are sodered at higher temperatures, due to the higher melting point of Pb free solder, but because we are military, we are still using lead solder on Pb free components. We are having to use Pb free components in places, due to discontinued Pb components.

We are buying 40 parts from Farnell, which may be a different batch number??? There are also 200 off arriving on the 18/12/06 that we could try. In the meantime, we are trying to understand why we are now seeing failures since we switched to the newer flash version.

We know it's not a board layout problem, because we have this micro on three different boards. Two of the boards that have the new flash have the cold start problem. The other board still has the old flash, however, I am being told by the PCB manufacturer today that 18/126 have also failed during functional test at 20C. They believe it is a flash problem and getting more old flash micro's to replace them.

We are currently monitoring the reset, supply and clocks and will let you know what we find. I can tell you that the micro is run from a 5V supply and the clk is buffered by a gate to the EXTAL input that is powered from a 2.4V zener. This is to meet to max XTAL input of 2.5V. Never had a problem with this in the past with the old flash micro, but could it be a tolerance issue with the new micro's?

Thanks,

LAR.

Re: MC9S12DG128 Cold start-up problem

LAR — Wed, 13 Dec 2006 00:20:26 GMT

Hi,

Thanks for the quick reply's.

Yes, only with the non B versions. The B versions are ok for cold starts.

Cheers,

LAR

Re: MC9S12DG128 Cold start-up problem

Alban — Wed, 13 Dec 2006 00:33:34 GMT

Well LAR,

It is probably best you have this issue followed closely by Freescale.

Submitting a Service Request will allow your problem to be reviewed confidentially.

May be the problem is lying in the initial Flash programming. It seems strange that a power cycle would solve anything in this case though.

This is such a very high failure rate that something is definitely wrong somewhere !

Alban.

Re: MC9S12DG128 Cold start-up problem

LAR — Wed, 13 Dec 2006 00:46:29 GMT

Thanks,

I submitted a service request earlier today, so I am awaiting a reply.

LAR.

Re: MC9S12DG128 Cold start-up problem

SteveRussell — Wed, 13 Dec 2006 04:40:27 GMT

A possible problem area is crystal oscillator start-up. I believe that there is folklore that low temperature startup is a symptom of not having the right component values in the oscillator circuit.

If the crystal start-up was marginal with the old part, some of the parameter variations in the new part may be enough to prevent low temperature start-up.

Have you reviewed the oscillator component values or tried changing them a little in the more drive direction?

Of course, you will have to retest high temp operation if you change them.

Re: MC9S12DG128 Cold start-up problem

rocco — Wed, 13 Dec 2006 06:32:43 GMT

Hi, LAR and Alban:

Alban wrote:
. . . It seems strange that a power cycle would solve anything in this case though.

It is actually normal behavior in a low-temperature situation. With the first power-up the die is cold, but it doesn't take but a few seconds of self-heating for the die up to reach a working temperature. The second power cycle just gives it a fresh chance to start-up.

Re: MC9S12DG128 Cold start-up problem

bigmac — Wed, 13 Dec 2006 14:31:16 GMT

Hello LAR,

Since you are using an external oscillator and buffer for the clock, I wonder if the problem could be in these components? It might be that the newer MCU type is more critical for clock amplitude, and perhaps also risetime, than the older part.

If the oscillator is sluggish to start at very low temperatures, this may account for what you are observing. This could be easily tested by delaying the release of MCU reset for an additional period - enough for the clock oscillator output to become stable, perhaps with a degree of self-heating of the oscillator also required.

Regards,

Mac

Message Edited by bigmac on 2006-12-1304:34 PM

Re: MC9S12DG128 Cold start-up problem

Lundin — Wed, 13 Dec 2006 15:51:56 GMT

As a sidenote, it is not only the flash that has been changed. 'B' versions (mask 0L85D and 1L85D) are filled to the brim with silicon bugs. There are erratas for pretty much every peripheral. You probably don't want to use 'B' if you are using things like SCI, SPI, flash security etc etc.

Re: MC9S12DG128 Cold start-up problem

LAR — Wed, 13 Dec 2006 20:59:54 GMT

Hi,

Thanks for all of the reply's.

We are investing the theory of the clock not being stable/correct amplitude at start-up for cold start-ups (thanks bigmac). The existing clock circuit has worked fine for the last couple of years and on various different boards with the same design, but using the 'B' version only. Maybe this new non-'B' version is more susceptable to a 'poorer' clock at cold temperature start-up's?

There appears to be a function to monitor the clock and switch to either the internal low frequency clock or do a reset. We are looking at modifying the code to keep resseting until a stable clock is achieved (saves changing any hardrware).

In the meantime, we are checking the operation of the clock circuit. The clock is a 16MHz oscillator (XO91100UIT-16MHZ from Euro-quartz). We buffer this using a single gate that is powered from a 2.4V zener diode to meet that max XTAL input of 2.5V. Also checking zener voltage at extreme temperatures.

Still awaiting a response from Freescale tech support!

Message Edited by LAR on 2006-12-1301:05 PM

Re: MC9S12DG128 Cold start-up problem

Lundin — Thu, 14 Dec 2006 15:57:43 GMT

To get a reset when the oscillator isn't working, simply disable the self-clock mode, bit SCME in register PLLCTL (it is enabled out of reset).

Re: MC9S12DG128 Cold start-up problem

LAR — Thu, 14 Dec 2006 16:33:19 GMT

Hi,

Thanks for the info, but how can you clear that bit in the code if the oscillator is not running and thus presumably no instructions are being executed?

Re: MC9S12DG128 Cold start-up problem

Alban — Thu, 14 Dec 2006 18:20:30 GMT

Hello LAR,

There is a stand alone clock inside the MCU.
It is called Self Clock Mode (SCM) and with the Clock Monitor (CM), you can get a Reset if the external oscillator is lost for a reason or another.
It is taking a reset vector called Clock Monitor Reset.

Alban,