CD74HC4060: Check Frequency/Time formula, tollerance vs temperature and other factors

V. Log

Part Number: CD74HC4060

Tool/software:

Hello everyone,

I am reviewing a control board circuit where the CD74HC4060 is used to enable and disable a part of the circuit after a fixed time.

With the following components:

Resistor: 78.7kΩ (RT0603BRD0778K7L)

Capacitor: 10nF (GRM2195C1H103FA01D)

Using the equation in the datasheet, I calculate a delay of approximately 14.2 seconds.

The reset pin is released via a 74HCT2G14 buffer, allowing the oscillator to start. Once pin 14 goes high, a MOSFET pulls down pin 11, stopping the oscillation.

However, when measuring the time between the reset deactivation and the output signal on pin 14, I observe around 14.8s, sometimes even up to 15s.

At low temperatures (-10°C to -25°C), the delay increases by an additional 200–300ms.

I have already estimated the impact of component tolerances and temperature coefficients (R and C), and the maximum I reach is around 14.5–14.6s.

So I’m wondering if I might be missing something—could temperature affect the internal oscillator of the 4060 more than expected? Are there any other consideration?

Also:

Does a pull-up/pull-down on pin 11 (OSC-IN) have any measurable effect on the oscillation frequency?

Are there any application notes or recommendations specific to this?

I cannot modify the design, but I can eventually adjust BOM values if necessary. I’m just trying to ensure my calculations are aligned with actual circuit behavior.

Thanks in advance for any insights.

3 months ago

0 Ian Graham 3 months ago

TI__Genius 9601 points

Hi,

Similar to our monostable multivibrator devices, we recommend real-life bench testing rather that relying solely on calculations. These devices are not made to be precise and have variance to them.

0 V. Log 3 months ago in reply to Ian Graham

Prodigy 10 points

Hi,

Yes, I fully agree that real-life testing is essential—and that’s exactly why I’m digging deeper into the observed discrepancies. My goal is to better understand the key contributors to the timing variance, so I can eventually fine-tune the RC values and stay on the safe side.

What I’m noticing is that the delay sometimes shifts even with small changes in power supply load. I found limited information in datasheets or application notes, but it’s clear that multiple factors are at play.

I’m not aiming for perfect precision—but I do need to know the expected range. In our application, exceeding a certain delay threshold is critical, so understanding the variance, and how to reduce it (especially in terms of repeatability across components), is quite important. A 1-second (on 14s) deviation feels quite significant for this context.

Any further insights or references would be really appreciated.

Thanks again!

0 Ian Graham 3 months ago in reply to V. Log

TI__Genius 9601 points

Hi,

Unfortunately, we don't have any specific information for the device or any guarantees of accuracy on the part of the timer.

Best,

Ian

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CD74HC4060: Check Frequency/Time formula, tollerance vs temperature and other factors