Thrifty 2-Hz Clock

Published:2011/8/12 1:13:00 Author:Amy From:SeekIC

P.C. Hogenkamp

CMOS circuits are known for their low current consumption. This is particularly important for battery-powered circuits. Unfortunately, oscillators often require quite a bit of current. We therefore pro­pose this oscillator circuit that has a very low current consumption (about 3 nA).

The circuit is powered from a type LM334Z current source. The current has been set with R4 to about 3μA. This is sufficient to power IC1 and the oscillator circuit around XI. The oscillator gener­ates, with the aid of a cheap watch crys­tal and a few surrounding parts, a signal that is subsequently applied to the divider in the 4060 and results in a frequency of 2 Hz at pin 3 (output Q13).

The level of the output pulses is a lot lower than the nominal 5-V power sup­ply voltage (IC1 is after all powered from a current source with very low cur­rent). That is why the signal on pin 3 of IC1 is amplified and inverted by Tl. IC3a finally turns it into a proper square wave with acceptably steep edges.

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