74HC4060 chip in 32.768 khz oscillator
--------------------------------------------------------------------------------
A few months ago you guys helped me in an interfacing HC-TTL to CMOS question. I was looking for a good oscillator circuit for 32.768 khz and was going to use a 4069 and a 74HC4060 to divide it down to 1Hz.
I took you up on your advice to just use the 74HC4060 as the oscillator, and then divide the 2 hz output with a flip flop (tried a 74HC74 but that didn't work so I ended up using a 74LS74 with great results). I got a nice 1 Hz pulse.
I built up several versions of the circuit (used the circuit at
**broken link removed** but had to change the 10 pF to a 22 pF and the 22 pF to a 25 pF trimmer to get dead on frequency with the crystal that I had).
My question is this. I have built three versions now:
one with a DIP 74HC4060 and DIP 74LS74
one with a DIP 74HC4060 and a SOIC 74LS74
and now one with a SOIC 74HC4060 and a SOIC 74LS74
I can't get the one with a SOIC 74HC4060 to work correctly. I removed the 74LS74 and am now experimenting with just the oscillator in an attempt to get it to work. I have tried several times with different chips, board layouts, crystals, etc. thinking that I had a bad part and I just can't get it to oscillate correctly. It either oscillates in the several hundreds of kilohertz range, or in the 20-30 Mhz range as measured both with a scope and a frequency counter.
Any thoughts? I hate to give up on this one but I can't figure out why there was never any problem with the DIP version but the SOIC version of the chip won't work in this circuit.
Thanks!
Chris
--------------------------------------------------------------------------------
A few months ago you guys helped me in an interfacing HC-TTL to CMOS question. I was looking for a good oscillator circuit for 32.768 khz and was going to use a 4069 and a 74HC4060 to divide it down to 1Hz.
I took you up on your advice to just use the 74HC4060 as the oscillator, and then divide the 2 hz output with a flip flop (tried a 74HC74 but that didn't work so I ended up using a 74LS74 with great results). I got a nice 1 Hz pulse.
I built up several versions of the circuit (used the circuit at
**broken link removed** but had to change the 10 pF to a 22 pF and the 22 pF to a 25 pF trimmer to get dead on frequency with the crystal that I had).
My question is this. I have built three versions now:
one with a DIP 74HC4060 and DIP 74LS74
one with a DIP 74HC4060 and a SOIC 74LS74
and now one with a SOIC 74HC4060 and a SOIC 74LS74
I can't get the one with a SOIC 74HC4060 to work correctly. I removed the 74LS74 and am now experimenting with just the oscillator in an attempt to get it to work. I have tried several times with different chips, board layouts, crystals, etc. thinking that I had a bad part and I just can't get it to oscillate correctly. It either oscillates in the several hundreds of kilohertz range, or in the 20-30 Mhz range as measured both with a scope and a frequency counter.
Any thoughts? I hate to give up on this one but I can't figure out why there was never any problem with the DIP version but the SOIC version of the chip won't work in this circuit.
Thanks!
Chris