#246 CMOS Oscillators
Testing a 4-pin CMOS oscillator component.
4-pin CMOS oscillators - like the SaRonix NCH060C I’m testing here - contain all the circuitry necessary to produce an oscillation when voltage is applied.
Internal details are hard to find, but I’m guessing NCH060C is a combination of crystal resonator with CMOS inverter gate and buffer.
Some oscillators feature “tri-state” control on one pad (the NCH060C does not have this feature). This effectively inhibits the clock output, and may be used for testing or for master circuit control.
Typical behaviour is as follows:
|Tri-state pin state||Output|
|no connect or a logic high||Enabled (clocking)|
|logic low||Disabled (no clocking)|
|1||tristate (n/a on the NHC)|
According to my oscilloscope, the NCH060C (20MHz) is running at 19.9996MHz - marginal difference that may be as much to do with my scope as the component itself. The signal appears to not be a perfect square wave (but I may be reaching the limits of my scope).
The MCO-1510A is a 1MHz CMOS oscillator.
|1||n/a (tristate on other models)|
Produces quite a clean square wave at 1MHz and 50% duty cycle.
Credits and References
- SaRonix NCH060C - the only good information I’ve been able to find about this particular oscillator
- MCO-1510A datasheet
- Oscillator FAQ - useful guide although for another product range
- Designing Crystal Oscillators with Modern CMOS Gates
- ..as mentioned on my blog