What are Main Crystal requirements?

[Singe12]

Hi all,

There's several crystal types with different ESR and Load Capacitance. What you've provided to us, inside datasheet, is a Frequency range between 2 and 40 Mhz and Frequency Stability of +/-10ppm.

I want to ask:
- There's also particular requirements about ESR and Load Capacitance?
- If I choose a crystal with a frequency that isn't a multiple of 40/20/10, can I get anyway 40/80Mhz on peripherals and 160Mhz as CPU clock?

Thank you!

[ESP_igrr]

I will need to check about the ESR, but for the second question, yes, you will be able to get 80/160/240 MHz CPU frequency and 80 MHz APB frequency. Crystal frequency determines CPU/APB frequency before the application startup, i.e. while first and second stage bootloaders are running. When application starts up, it enables PLL and switches the clock source to that.

[ESP_igrr]

Got reply from hardware guys:

Generally, once the crystal could start up to a certain amplitude, it would meet our requirements.
So don't worry about the ESR or load cap.

[kostyan5]

Current data sheet and hardware design guide for ESP32 only mentions the frequency of the main crystal. Are there stability and accuracy requirements? We currently use 10ppm, but 40-50ppm are cheaper. Are those an option?