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Will high but narrow current spike damage microcontroller?

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eem2am

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Hi,

Will the current spike in the capacitor C1, below, eventually destroy the microcontroller.......?

............because it will be above the 25mA maximum output current of the microcontroller.?

,,,,Microcontroller 1 is sending bits to microcontroller 2 at 12KHz…..

Schematic:
https://i52.tinypic.com/15n0u9h.jpg







Microcontrollers are MC9S08AC60CFGE.
The micro’s are supplied by 5V.

Page 304 of the MC9S08AC60CFGE microcontroller datasheet states that the maximum instantaneous current allowable in a microcontroller pin is 25mA

Page 304 of MC9S08AC60CFGE microcontroller datasheet:
https://i51.tinypic.com/4rtj00.jpg


MICROCONTROLLER DATASHEET (Freescale MC9S08AC60CFGE):
https://cache.freescale.com/files/mic...f?fsrch=1&sr=5
 

I suppose that this is a digital signal transfer,
why don't you use 10 times bigger resistor and 10 time smaller capacitor to have the same result but within current limits (10mA from 5v) for the output?

Alex
 
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    eem2am

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The datasheet answers the question indirectly, because a load of 50 pF without series resistor is applied in the datasheet rise-time specification. It results in a peak current of 67 mA for the typical tr,10,90 of 3 ns.

So, as mentioned in your previous thread, the 25 mA number can't be a sufficient specification. Actually, no designer would think about peak current limits when connecting 50 or 100 pF to an output directly, The more interesting case would be with 500, 1000 or more pF.
 
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