DS3231 (RTC/Counter) Alternative? - Page 1
Forum section: electronics / projects

author: ANTALIFE
author_rank: Frequent Contributor
timestamp: August 18, 2019, 08:37:21 am
content: Hi AllI am trying to pick out an RTC/counter for my solar powered weather station. Since the unit will be solar powered (and use a super capacitor for energy storage) my main requirement is low power (<1uA). Secondary requirement is accuracy as all I need to do is see if ~7days have passed since recording one of the sensor values (SGP30 base value)I have been looking at some RTC's & counters and it seems that the DC3231 is quite popular, but since this part is 14 years old (came out in 2005) I was wondering if anyone had a recommendation for any newer/better parts?Cheers, AntonEDIT: Also here are the parts I have looked at so far (most are from Maxim):RTC's:DS3231 [2.3V to 5.5V, 840nA, Has backup battery connection, Integrated crystal, Very popular]DS1339 [1.8V to 5.5V, 400nA, Has backup battery connection, External crystal]MAX31342 [1.8V to 3.3V, 150nA, External crystal, Very new (2018)]Counters:DS1374C [2.97V to 5.5V, 400nA, Has backup battery connection, Integrated crystal]DS1372 [1.3V to 5.5V, 400nA, External crystal]DS1371 [1.7V to 5.5V, 800nA, External crystal]DS1672 [1.8V to 5.5V, 425nA, Has backup battery connection, External crystal]

author: iMo
author_rank: Super Contributor
timestamp: August 18, 2019, 12:26:54 pm
content: There is none better alternative, afaik.

author: Skashkash
author_rank: Regular Contributor
timestamp: August 18, 2019, 01:27:35 pm
content: Don't know if better, but cheaper and with a couple of extra features.NXP has some TCXO RTCs (500na +/- 3ppm)Like the PCF2127

author: Unixon
author_rank: Frequent Contributor
timestamp: August 18, 2019, 01:31:12 pm
content: Quote from: ANTALIFE on August 18, 2019, 08:37:21 amYou say this like it's something bad to be a 14 years old part. If DC3231is still in active production I see no problem here.My own issue with DC3231 is its huge package size. Is there anything smaller with nearly same precision?

author: ANTALIFE
author_rank: Frequent Contributor
timestamp: August 18, 2019, 10:52:08 pm
content: Quote from: Unixon on August 18, 2019, 01:31:12 pmI am quite new to RTC's but from my experience with OPAMPs/MOSFETs/MCU's/sensors... a lot changes in 14 years, and you are better off going for the newer parts

author: iMo
author_rank: Super Contributor
timestamp: August 19, 2019, 09:31:38 am
content: The DS3231 is not in production, afaik. There is the DS3231M (MEMS based) in the production with lower specs, however..

author: Marcus Bockting
author_rank: Newbie
timestamp: May 05, 2020, 06:31:25 pm
content: Hi,if that is still a topic you could look out for the RV-3028-C7.It has 1ppm and 40nA.I think this is the best alternative to the DS32xx.https://www.tindie.com/products/19912/Marcus

author: cdev
author_rank: Super Contributor
timestamp: May 05, 2020, 07:52:26 pm
content: I have a much older Dallas RTC in a small computer (a cobalt cube2) that I recently plugged in after it had been turned off since its external power supply failed, coincidentally, around 2005, 15 years ago.The RTC was still runningand when I figured in the three hours time difference it wasnt off by that much. (I forget exactly how much though) . The time servers etc. were not able to update the time since the net has changed a lot since then so I am certain that its still on the wrong time. It would be interesting to figure out the error. Not too shabby.You definitely should be able to improve on a 15 year old part. Have you thought of energy harvesting electricity somehow? You can probably get enough electricty to run some parts literally out of the air, as long as the various transmitters all around us keep running. And if they all stopped, you'd (we would all) likely have other bigger problems than some device failing.

author: DrG
author_rank: Super Contributor
timestamp: May 06, 2020, 12:14:51 am
content: https://ambiqmicro.com/static/rtc/files/AM18X5_Data_Sheet_DS0003V1p3.pdfhttps://www.emmicroelectronic.com/sites/default/files/products/datasheets/3028-FS_0.PDFNot sure those two are easily available in single quantities but they show up in a quick search. I would be inclined to use the MAX3134Bhttps://www.maximintegrated.com/en/products/analog/real-time-clocks/MAX31341B.html/tb_tab1which you already mentioned.

author: dmendesf
author_rank: Frequent Contributor
timestamp: May 06, 2020, 05:41:41 am
content: You must first decide if you want a TCXO-based RTC or not. The difference is night and day for performance as you can see in the graph, but power consumption is worse. If you want a TCXO-based RTC the only options I know about are DS3231/DS3234, PCF2127/PCF2129 and RV3028C7.

author: james_s
author_rank: Super Contributor
timestamp: May 06, 2020, 06:09:04 am
content: Quote from: ANTALIFE on August 18, 2019, 10:52:08 pmAn RTC is not a mosfet/mcu/sensor.Perhaps it's better to ask what do you find lacking in the DS3231 that you are hoping will be improved on a newer part?

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: May 12, 2020, 11:07:59 am
content: Isn't theMicro Crystal RV-8803-C7the gold standard in temperature-compensated RTCs? Tiny package, 250 nA, 100ths of seconds, etc. Problem is it's expensive, $1.50 in quantity.

author: james_s
author_rank: Super Contributor
timestamp: May 12, 2020, 05:27:41 pm
content: $1.50 is expensive?The DS3231 is 2-3 times that price in qty 1,000, you can buy them much cheaper from China and those parts have always worked perfectly fine for me but I don't know whether they're legit or not.