32.768kHz RTC Crystal recommendation

tc9201
Posts: 4
Joined: Mon Dec 03, 2018 3:59 am

32.768kHz RTC Crystal recommendation

Postby tc9201 » Mon Dec 03, 2018 4:20 am

Hi, wondering if someone could tell me the manufacturer/part number of the 32.768KHz RTC crystal used on the ESP-WROVER-KIT. Or manufacturer/part numbers for 32.768k crystals that Espressif recommends. I'm having the following issue with my prototype PCB.

I currently have a Qantek QTP7-32.768-12b20 xtal on my PCB connected to GPIOs 32,33 of an ESP32-DEVKITC-32. But I am not reliably getting the 32k clock (measuring this on GPIO25 ie buffered). I've tried various cap values for the 2 (pierce osc) caps, but can't seem to get a reliable 32k clock (when tried on a number of my PCBs). BTW, PCB traces are short, but I have the ESP32-DEVKITC connected to the PCB through a header socket - I'm sure this doesn't help but I do need to have this header socket, as least initially. Any help appreciated.
thanks
tc

username
Posts: 141
Joined: Thu May 03, 2018 1:18 pm

Re: 32.768kHz RTC Crystal recommendation

Postby username » Mon Dec 03, 2018 6:34 am

Just for trials did you remove the xtal from a ESP32-DEVKITC-32 and try it on yours to verify ?

tc9201
Posts: 4
Joined: Mon Dec 03, 2018 3:59 am

Re: 32.768kHz RTC Crystal recommendation

Postby tc9201 » Mon Dec 03, 2018 10:41 am

The ESP32-DEVKITC doesn't have the 32k xtal, so I assume you meant the ESP-WROVER-KIT... unfortunately, the xtal on the ESP-WROVER-KIT has a different footprint to what I have on my PCB, so it'll be difficult to solder onto my PCB. But I'm interested to see the datasheet on this Xtal as it may give me some clues to other xtals I can try, or maybe I'll just respin the PCB to take this xtal. Thanks

tc9201
Posts: 4
Joined: Mon Dec 03, 2018 3:59 am

Re: 32.768kHz RTC Crystal recommendation

Postby tc9201 » Mon Dec 03, 2018 10:44 am

Anyone from Espressif on this forum who can provide the part number for 32.768k xtal thats on the ESP-WROVER-KIT?

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loboris
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Joined: Wed Dec 21, 2016 7:40 pm

Re: 32.768kHz RTC Crystal recommendation

Postby loboris » Mon Dec 03, 2018 3:30 pm

I'm using this one with 12pF capacitors on my custom boards with ESP32-WROVER and never had any issue.

tc9201
Posts: 4
Joined: Mon Dec 03, 2018 3:59 am

Re: 32.768kHz RTC Crystal recommendation

Postby tc9201 » Tue Dec 04, 2018 2:12 am

Thanks Loboris, appreciate the help. I'll give this a go. But I'd still like to know the xtal used on the ESP-WROVER-KIT - Espressif???

kengster
Posts: 7
Joined: Fri Dec 06, 2019 8:32 pm

Re: 32.768kHz RTC Crystal recommendation

Postby kengster » Fri Dec 20, 2019 2:35 pm

Hi all, I am on the same situation. I would like to add an external crystal in order to use BLE modem sleep and save power, but I do not know which crystal is recommended, if there is any special brand.

Cheers.

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