Crystal Oscillator source
Posted: Sun Aug 17, 2025 11:24 am
Hello
I am an Electrical Engineer and I make a project with your ESP32
i have a few question regarding the differences between the Hardware Design Guidelines(HDG) and i would really like you to help me with that
First of all i would like to know what HDG should i follow given an ESP32?
should i look when it was bought and follow the last document back there? or follow the latest version?
Does the update at HDG influence other batches as well? (I mean Batches created before the update)
All of the questions are regarding XTAL_P pin - external Clock Source\Crystal
1) i saw a difference 2018 HDG v2.5 and 2021 HDG v3.2
in v3.2 you added 2 things:
a) the amplitude into XTAL_P can not exceed 1.1V
b) if an oscillator is used' its output should be connected to XTAL_P on the chip through a DC blocking capacitor (about 10pF)
Can you please tell me why you changed those(especially the amplitude limitation)?
What will be the consequences if I use a Crystal Oscillator at 3.3V?
i saw in the revision history relevant updates at: v2.4 and v3. but i dont know what changed and why
2) i saw a difference 2022 HDG and 2024 HDG
you changed the whole title from External Clock source to External Crystal Clock Source
Basically, you removed the option to put a crystal Oscillator in XTAL_P pin
I would like to know why?
can you please tell me what will be the consequences of putting a Crystal Oscillator at 3.3V at XTAL_P?
I saw in revision History updates at:
- v1 - the migrated from PDF to HTML format changes
- v1.7 - crystal section
a few years back my friend did a similar project and he put a 3.3V Crystal Oscillator at the XTAL_P pin.
can i use a Crystal Oscillator at 3.3V in XTAL_P pin? and what will be the consequences?
Lastly, I would like to know if I do use an Oscillator. What are the guidelines of the design? should i put the Crystal Oscillator close or far from the ESP32?
thanks in advance
I am an Electrical Engineer and I make a project with your ESP32
i have a few question regarding the differences between the Hardware Design Guidelines(HDG) and i would really like you to help me with that
First of all i would like to know what HDG should i follow given an ESP32?
should i look when it was bought and follow the last document back there? or follow the latest version?
Does the update at HDG influence other batches as well? (I mean Batches created before the update)
All of the questions are regarding XTAL_P pin - external Clock Source\Crystal
1) i saw a difference 2018 HDG v2.5 and 2021 HDG v3.2
in v3.2 you added 2 things:
a) the amplitude into XTAL_P can not exceed 1.1V
b) if an oscillator is used' its output should be connected to XTAL_P on the chip through a DC blocking capacitor (about 10pF)
Can you please tell me why you changed those(especially the amplitude limitation)?
What will be the consequences if I use a Crystal Oscillator at 3.3V?
i saw in the revision history relevant updates at: v2.4 and v3. but i dont know what changed and why
2) i saw a difference 2022 HDG and 2024 HDG
you changed the whole title from External Clock source to External Crystal Clock Source
Basically, you removed the option to put a crystal Oscillator in XTAL_P pin
I would like to know why?
can you please tell me what will be the consequences of putting a Crystal Oscillator at 3.3V at XTAL_P?
I saw in revision History updates at:
- v1 - the migrated from PDF to HTML format changes
- v1.7 - crystal section
a few years back my friend did a similar project and he put a 3.3V Crystal Oscillator at the XTAL_P pin.
can i use a Crystal Oscillator at 3.3V in XTAL_P pin? and what will be the consequences?
Lastly, I would like to know if I do use an Oscillator. What are the guidelines of the design? should i put the Crystal Oscillator close or far from the ESP32?
thanks in advance