CD4060 oscillator, max resistor value

Hello Folks,

Got a design here that contains a few 4060 long timers with RC oscillators. Battery operated so consumption counts. Some datasheets state that the maximum value for any resistor in that area is 1M. Since Rs (feedback resistor) must be at least twice Rt (timing resistor) this leads to rather lowish timing resistor values. Since this is a logic gate oscillator that requirement causes quite some current at voltages around 10V.

Anyhow, the TI data*** does not seem to state that maximum:
http://focus.ti.com/lit/ds/symlink/cd4060b.pdf

.... while ON-Semi does state a 1M maximum:
http://www.onsemi.com/pub/Collateral/MC14060-D.PDF

What gives? Why do some specify that max value as low as 1M for really low leakage CMOS logic? A remnant from the olden days when this stuff was leaky at times?

I usually use my own oscillators around CD40106 but this time those are all used up and there ain't no space no more :-(

--
Regards, Joerg

http://www.analogconsultants.com
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