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Problems with MC74HC4060ADxxG. We use it as a counter for watchdog application with an rc oscillator. The freq on pin 9 is about 555Hz, according data sheet the freq should be 404Hz. We have also noise on the Clock Output (OSC_OUT_2 Pin9 which causes that Q4(pin 7) switches to fast (Rs=24.9k on pin 11 Rct=8.25k on pin 10 Cct=100nF on pin 9). Are all values in the design correct or there are hints which can explain the noise? Thanks Florian

The oscillation frequency could be different than the calculated value due to a couple of reasons. First, the tolerances of the R and C components are contributed to the error, in addition to the MC74HC4060A.

This data sheet does not specify accuracy for the RC oscillator; however, the typical accuracy is +/-10%. The relatively large size of the capacitor or low frequency also is contributing to the error. The frequency equation matches the measured value closer at higher frequencies. One possible cause of the noise on the output could be instability of the supply voltage. We recommend adding 0.1uF decoupling capacitors as close to the IC as possible.
Answered by:
ON Semiconductor
2014-09-15 01:30:07.349