Inaccurate DS1307

Looking at the Frequency Range table it looks like 45K. It does not say whether the values are typical or maximum specifications.

Also mentioned in the datasheet is a special crystal "specifically designed for the Dallas RTC". Did you get the standard crystal or the special one?

(* jcl *)

I forgot to add the crystals that I like to use with the Dallas/Maxim chips are the Citizen CFS series. These are specified for a maximum ESR of 35K (as long as you use a 3x8 or 2x6).

My board is at

(* jcl *)

www: twitter: blog:

Yeah, on re-reading the datasheet I see that it has an ESR of 35kOhm @32.768kHz..

I have no idea. I have the one linked in the original post, but there is no indication if it's specifically for the RTC or not. However, there are only a very limited range of crystals from that supplier, and I suspect that it's the general one. It's handy for me to use CPC (part of the Farnell group) as they have a warehouse outlet next door to where I work.

All the indications at the moment are that the second crystal is working just fine, it appears that the first one may just be faulty.

Crystals are, er, crystal (quartz crystal), and subject to damage from shock. If it got dropped on a tile or concrete floor, it could be damaged.

A specific crystal ground plane would be something for a custom PCB design.


I have SparFuns pre assembled and mine is of by 6 sec/day, will get a new crystal to see if this one is damaged. Else i will get a DS3231, both cheaper and has a temp compensation.