I am currently using a 74LV123A to generate a 29 mS pulse. R = 294K and C = 0.1uF. I recently determined that the pulse is varying too much in width because of the 5% (X7R) tolerance on the capacitor. In order to increase accuracy, I'd like to switch to a 1% capacitor (C0G). The board is already in production and the capacitor must be a SMT 0603 size part. The biggest stock capacitance I can get in C0G in an 0603 package is 0.01uF. To get the same pulse width, I'll need 10X the resistance or almost 3 Meg. Can anyone comment on how practical it will be to use that high a resistance and if it will result in better accuracy?
I dont know at what point the resistor will no longer have any effect. I suspect 3 meg is beyond that point.
Here is an appnote that may help. http://focus.ti.com/lit/an/scla014/scla014.pdf
Thanks for the opinion.
NXP's datasheet actually specs 1M as the max and I would imagine that it is probably a good rule of thumb to apply to the TI part as well. I don't think going with a 3M resistor will solve my problem, so I'll try other solutions.
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