Atmel 1200A question..

[mramos1]

I have an existing circuit and it just kills batteries to fast. It is a chip (AT90S1200A-12) running on the internal 1Mhz OSC.

I had a pic circuit that did the same and I wound up dropping it to 32.7Khz and rewriting all the timing loops.. PIC worked fine.

Just tired with the Atmel 1200 circuit , and I have a funning feeling Atmel will not run that slow. The caps are 15pf..

I have not dug out the scope yet. I re-enabled the internal OSC and put delays back and it runs fine.

The data sheets mention 12Mhz and internal 1Mhz.. Will I be re-doing it all over on a PIC??

 

[Nigel Goodwin]

Read the datasheet, PIC's operate from DC to their maximum frequency, perhaps AVR's do the same?.

Are you sure the consumption is purely down to the AVR?, it's not external circuitry causing the drain?.

What level of consumption are you talking about anyway?.

 

[mramos1]

I am running on 150ma watch batteries, it had to be real small. I get about 10 runs at 2 hours on it. Which is not the end of the world. But I had that
LDR circuit and you mentioned doing it.. I did it on the 12F509, fired right up..

I was real careful soldering the xtal as well, barly touched it with the iron..

I will get the scope out later and see if it there is 32Khz on the chip.

I know with some microcontrollers, they have a speed range and that is it.
I googled for Atmel 1200 and Khz and did not see anyone else doing it as well.

Thanks

 

[hjames]

The 1200 is pretty ancient - It's probably Atmel's equivalent to the 16F84... From it's data sheet, it says it can operate down to DC, but using a 32KHz crystal will probably require some tuning - and power limiting.

I stumbled across this appnote on tuning fork crystals, it has some sample 32KHz oscillators, with parts values, and the reasoning behind the choices.

**broken link removed**

 

[mramos1]

hjames: Thanks that gives me some ideas (the link). I will try 33pf, and a 20meg load across the xtal and see what happens.

Thank for finding that. Perfect.