Author Topic: DS3231 (RTC/Counter) Alternative?  (Read 4607 times)

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Offline ANTALIFETopic starter

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DS3231 (RTC/Counter) Alternative?
« on: August 18, 2019, 08:37:21 am »
Hi All

I 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, Anton


EDIT: 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]
« Last Edit: August 18, 2019, 09:29:39 am by ANTALIFE »
 

Offline iMo

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #1 on: August 18, 2019, 12:26:54 pm »
There is none better alternative, afaik.
Readers discretion is advised..
 

Offline Skashkash

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #2 on: August 18, 2019, 01:27:35 pm »
Don't know if better, but cheaper and with a couple of extra features.

NXP has some TCXO RTCs  (500na +/- 3ppm)

Like the  PCF2127

 

Offline Unixon

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #3 on: August 18, 2019, 01:31:12 pm »
DC3231 is quite popular, but since this part is 14 years old (came out in 2005)
You 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?
 

Offline ANTALIFETopic starter

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #4 on: August 18, 2019, 10:52:08 pm »
DC3231 is quite popular, but since this part is 14 years old (came out in 2005)
You 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?

I 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

Offline iMo

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #5 on: August 19, 2019, 09:31:38 am »
The DS3231 is not in production, afaik. There is the DS3231M (MEMS based) in the production with lower specs, however..
Readers discretion is advised..
 

Offline Marcus Bockting

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #6 on: May 05, 2020, 06:31:25 pm »
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
 
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Offline cdev

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #7 on: May 05, 2020, 07:52:26 pm »
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 running and 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.
« Last Edit: May 05, 2020, 07:59:06 pm by cdev »
"What the large print giveth, the small print taketh away."
 
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Offline DrG

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #8 on: May 06, 2020, 12:14:51 am »
https://ambiqmicro.com/static/rtc/files/AM18X5_Data_Sheet_DS0003V1p3.pdf

https://www.emmicroelectronic.com/sites/default/files/products/datasheets/3028-FS_0.PDF

Not sure those two are easily available in single quantities but they show up in a quick search. I would be inclined to use the MAX3134B https://www.maximintegrated.com/en/products/analog/real-time-clocks/MAX31341B.html/tb_tab1 which you already mentioned.
- Invest in science - it pays big dividends. -
 
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Offline dmendesf

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #9 on: May 06, 2020, 05:41:41 am »
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.
 
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Offline james_s

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #10 on: May 06, 2020, 06:09:04 am »
I 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

An 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?
 

Offline I wanted a rude username

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #11 on: May 12, 2020, 11:07:59 am »
Isn't the Micro Crystal RV-8803-C7 the gold standard in temperature-compensated RTCs? Tiny package, 250 nA, 100ths of seconds, etc. Problem is it's expensive, $1.50 in quantity.
 

Offline james_s

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Re: DS3231 (RTC/Counter) Alternative?
« Reply #12 on: May 12, 2020, 05:27:41 pm »
$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.
 


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