#294 CD4060 Crystal Oscillator

Exploring the behaviour of the CD4060 ripple counter driven by a crystal oscillator.

Build

Notes

The CD4060 datasheet describes a crystal oscillator configuration for self-driving the ripple counter. The use of a crystal provides very precise (but fixed) frequency control.

CD4060_crystal_oscillator

See the LEAP#293 CD4060/RCOscillator project a similar circuit that is RC controlled, thus allows variable frequency control.

In this test I’m using a 32.768kHz crystal. The resulting oscillation looks like this (tapped at the net marked CH2 in the schematic):

scope-oscillator

Ripple Counter

The CD4060 is a 14 stage ripple counter constructed of RS flip-flop units - see the functional diagram from the datasheet:

CD4060_functional

The input signal passes 4 stages before the first output is tapped (Q4). Thus the first (Q4) output signal divides the input frequency by a factor of 2^4

Stage 11 (Q11) of the ripple counter is also not exposed on a pin.

The lack of Q0-3 and Q11 is I think just pin economics so it all fits it in a DIP16 package.

The performance is summarised in the following table and the logic analyzer (LA) capture. While 32.768kHz may sound like an odd crystal frequency, the table below gives away its purpose: the ripple counter divides this frequency into lots of familiar powers of 2! Also note how under crystal control, the actual frequency (as measured with an oscilloscope) is exactly equal to the theoretical frequency.

Signal	LA	Frequency (theory)	Frequency (actual)	Note
CH2		32768Hz	32768Hz	f-input
Q4	07	2048Hz	2048Hz	f-input/2^4
Q5	06	1024Hz	1024Hz	f-input/2^5
Q6	05	512Hz	512Hz	f-input/2^6
Q7	04	256Hz	256Hz	f-input/2^7
Q8	03	128Hz	128Hz	f-input/2^8
Q9	02	64Hz	64Hz	f-input/2^9
Q10	01	32Hz	32Hz	f-input/2^10
Q12	00	8Hz	8Hz	f-input/2^12
Q13		4Hz	4Hz	f-input/2^13
Q14		2Hz	2Hz	f-input/2^14

Construction

Breadboard

Schematic