Voltage monitor for car battery

[Andy Wood]

Are you sure you have the correct data sheet. Section 12.1, paragraph one in the data sheet titled PIC16F87/88 clearly states "The maximum recommended impedance for analog sources is 10K."

I do agree one needs to stay within the specifications if you do not want to see the magic smoke

Now there's a trap - the current datasheet from Microchip states 10k:

http://ww1.microchip.com/downloads/e...Doc/30487c.pdf


However, the (older) datasheet on the melabs site states 2.5k:

http://melabs.picbasic.com/devicedata/30487a.pdf


A good lesson - always ensure you have the latest datasheet!!!

Regards,

Andy

[mackrackit]

And to make sure you are not using old parts. MicroChip seems to make improvements every so often. With all of their products it is hard to keep up.

But I have to wonder, impedance being an AC term, does this apply more to an ADC source that is switching? Like an old load cell driver?

But as far as the original question on this thread, I think it has been answered and designed. Thanks to Adam.

[Pic_User]

Thanks goes to the Circuit Design Committee for the input and to passion1 for asking the all important question.
Great job nailing down the 2.5k 10k discrepancy, I replaced my old PIC16F88 sheet with the newer one.
-Adam-

[mackrackit]

Circuit Design Committee

I like that.