Electronics > Projects, Designs, and Technical Stuff

Modern equivalent of 74HC4046 PLL?

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Miti:
I hope you're all doing well,

I'm looking for a PLL/VCO chip that can extract the pixel clock from the horizontal sync pulses. The pixel clock is 21MHz, the horizontal sync is around 15KHz.
I tried HC4046 and used this calculator for the passives:

https://www.changpuak.ch/electronics/calc_03.php

It is very jittery and it only reaches 21MHz with C1 out of specs, <40pF when it needs to be >40pF. I suspect 15KHz is a bit low and the VCO is pushed to the limits.
The divider is in an FPGA and that part works well.

Do you know any simple chip that can do that?

Thanks!

Karel:
Never use that chip, use the Nexperia 74HCT9046 instead. It's much more stable.

https://assets.nexperia.com/documents/data-sheet/74HCT9046A.pdf

jpb:
This application note might be relevant:
https://www.ti.com/lit/an/scaa088/scaa088.pdf
It is audio but at similar frequencies going from a few 10s of KHz to 10s of MHz.
The 4046 is only used for its phase detector while another chip is used for the PLL.

Kleinstein:
For slightly higher speed there is a 74LV4046.

Miti:
Thanks for your replies and I apologise for my slow response. I was busy with... life.

@ Karel
Yes, I read somewhere that 4046 is crap. I used TI HC404AM because it is specified at 3.3V but I guess I need 5V to make it work at 21MHz. Or at least get the least crappiness out of it.

@jpb
Nice and clean solution but it is quite expensive and it needs I2C and a pullable 21MHz crystal. Unfortunately Digikey doesn't carry any 21MHz crystal.

@Kleinstein
I'm trying to find a 3.3V device first.

Technically I only need a VCO that can do 21MHz, I can implement the phase and frequency comparator inside the FPGA.

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