Automotive temp MCU

Its also marketing. Selling a board for 125C operation and using chips clearly marked for 85C that control power to the rest of the board can be hard to explain. I'd rather let my customers have confidence in the chips that I pick rather than asking them to have confidence in me (an unknown to many of them).

Take a look at the Zilog eZ8 family ?

If you like the AVRs, imagine adding a register Frame pointer, and some efficent direct memory opcodes, and you are close to a Z8

eZ8's come in extended temp (-40'C to 105'C), which is a gain on your "sleep above 85'C" - they start at SSOP20, and go up to 80 pins.

System wise, I'd design in as much thermal inertia as possible, get power-paranoid to reduce the self-heating, and record/log the actual temperatures, as well as do a memory checksum and train (sic) the customers they need to replace your modules after so many LogT * Hours product.

-jg

Motorola are very good for automotive temperature parts. Visit

I don't think you'll find much for under $3 though. A reprogrammable HC05 of HC11 will cost you significantly more than that.

I think a PIC may be your best bet. They work reliably at 125 ambient and fit your price requirement.

Andy

I think you may need to look at a more recent price list (or maybe just a more recent part). Newark's single-piece price for a

The QT4 gives you a much nicer core and more Flash (4k vs. 1k)and RAM (128 bytes vs. 64 bytes) than a PIC12F675, but the I/O is not quite a flexible. Digikey's price for the PIC in the extended temperature range is $2.30 for 1, $1.48 for 25. I can't give you Newark's price because they don't carry the right temperature grade. And so it goes...

Regards,

-=Dave

Thanks for the info. I have looked at the Motorola stuff. As you say, they have good parts, but they are not in the price ball park. I may revisit them just one more time. I seem to remember looking at some of their larger 8 bit parts before and found that their ADCs could not work with an external reference and don't have an internal one. It uses the Vdd level as the ADC reference. I tried to discuss this with them and the problems it can create since most Vdd sources are not better than about +-3% once you add in the tolerance of the set resistors. But they seemed to think this was not an issue. So what is the point of having a

Thanks for the info Dave, but this chip only comes in 8 pin packages. I need at least 20 pins and am more comfortable with 28 (20+ IOs). The Motorola site lists the 1k price as about a buck, but then a lot of 8 pin MCUs are a buck.

MC68HC908JL3 - LQFP48 -

I'm baffled by all the postings I've seen on this thread. In one of them it was said that the application was instru- mentation for a locomotive, but there's an obsession with finding the physically smallest MCU possible; given the size of most railroad locomotives, it's hard to imagine size being particularly critical.

It was not stated as to whether test instrumentation or permanent, operational instrumentation was meant, but if the former, it's hard to imagine a slight difference in price of an MCU being much of a factor; if the latter, given the multi-million dollar price of locomotives, a dollar or two difference in the price of an MCU is negligible.

Another posting said something about wanting to monitor Vdd. This would seem to be a matter of trying to measure a voltage with the voltage being measured, regardless of how one goes about doing it. It's also hard to imagine a need to monitor Vdd (except for operating/fail) in any event.

Sounds like a batter-powered instrument of some kind, maybe specialized data logger.

Best regards, Spehro Pefhany

This board is for multiple applications. The locomotive app was one that illustrates the need for high temperatures.

Again, this board is to be sold for multiple apps. A dollar may not make a big different in the end cost, but if selling 10,000 units over the next few years, a buck parts savings will provide an additional $10,000 in profits. Certainly it is worth a thorough examination of the available parts.

Since when is Vdd used as a reference for measuring *anything*? That was my point. Some of the chips use Vdd as the refernce for the on chip ADC. With most Vdds being 2 or 3% accurate, this seriously degrades the performance of the ADC. Most boards these days have multiple power supplies on board. This board will have five DCDC converters and will have two separate 5 volt sections.

I find that most engineers want to rework the problem that is being solved. I have minimized the solution to either one chip or two. Now I am just trying to find the best choice to suit that decision. In any case, this chip must meet automotive temps.

I have been told that the Cypress PSOC chips will be available in automotive temp range shortly. If I can confirm that, this may be a $2, one chip solution. Smallest size (QFN), lowest cost and fewest chips; I see that as worth a few days of searching.

"Spehro Pefhany

Yes, many of the apps for this board are remotely located, running off batteries. The board shuts down and only has to power the RTC in this section of the board. When needed, it wakes up and runs the DSP application and returns to slumber. Some customers only need to run a couple of times a day for a few seconds. So the power of the sleep circuit can still be significant if it is too high.

I used to be a Z8 fan, but the brain-damaged implementation of a UART was = a serious impediment. Did that get fixed on the way to the eZ8?

The Super8 was a much better device, but they shot that one out from under = us a few years ago, and with almost no advance notice. That left me little = confidence in Zilog as a supplier.

serious impediment. > Did that get fixed on the way to the eZ8?

The eZ8 UART looks at the top end of uC uarts - it has TX Shift and TX hold empty, as well as CTS hardware flow control, and parity/address recognize/BRG/Break , and IRDA pulse modes too..

a few years ago, > and with almost no advance notice. That left me little confidence in Zilog as a supplier.

Technically, one might have expected the FLASH devices to choose the Super8, but I guess commercial reality hit, and they decided to just do OTP -> FLASH on a family that has some market coverage.

-jg

I think that you can get some Atmel Flash 8051s (at least the T89C51CC01 CAN version) in full Automotive temp but I do not have the full list. Check with your local Atmel FAE.

I sent an email to Dan Ujvari, but I have not received a reply. Of the

Since this chestnut is a common one, I did see Atmel have posted new data on their ATAM893-J

This has both wide Vcc (1.8-6.5V) and Wide Temp (-40'C..+125'C) and good low power operations of 32Khz clock engine (< 1uA). Would make a good extremes system power sequencer / wdog / general health monitor...

-jg

The AT89C51CC01 is also coming in Automotive temp.

This is of interest to me. I looked at this data sheet and could not find any significant differences to the ATAM893-V. Both are wide temp and the rest seems to be the same except for notes about how the -J version has a 5% faster clock (on the average) compared to the ROM parts and the -J version the lack of selectable high drive outputs on the -J version, again compared to the ROM versions, not the -V.

Anyone see a significant difference between the -J and the -V versions? Did I miss something big?