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Which one is better? DS3231SN have accuracy ±2ppm and the other one have ±5ppm.What is actually meant by the accuracy and what are the other differences.? What type of internal oscillators are used by both? Which one is better to use for a alarm function and reduced board space. I have written the program for DS3231SN and is work for DS3231MZ?

Pleas help me

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I have no idea about what you mean with "better".

ppm means "parts per million". If it says +/-5ppm for accuracy then it means that chip can shift 5 seconds (up or down) in 1 million seconds. In other words, the chip has a 5us (microseconds) accuracy.

Practically thinking, in 1 seconds, the chip can count between 0.999995 and 1.000005 seconds.

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  • \$\begingroup\$ Yeah thank you. Better means which is more accurate. From your information i can say that MZ is more accurate. I want to know one more thing about the oscillators used in both? \$\endgroup\$ – vishnu m c Apr 7 '17 at 5:02
  • \$\begingroup\$ @vishnumc The DS3231MZ (+/-5ppm is definitely NOT more accurate than the DS3231SN (+/-3.5ppm). The 'MZ uses a much cheaper and less accurate MEMs oscillator compared to the 32 kHz crystal used in the 'SN. The electronics appear identical in both versions \$\endgroup\$ – Jack Creasey Apr 7 '17 at 5:50
  • \$\begingroup\$ @vishnumc No! DS3231S is more accurate (±3ppm) than DS3231M (±5ppm)! I don't know anything about your application and needs, though. Maybe DS3231M can be acceptable for you since it's cheaper than S one. \$\endgroup\$ – Rohat Kılıç Apr 7 '17 at 5:52
  • \$\begingroup\$ can you please say about how much the IC DS3231SN can count? \$\endgroup\$ – vishnu m c Apr 7 '17 at 5:57
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There are two different datasheets.

  • DS3231S# ..... 0°C to +70°C SO16
  • DS3231SN# . -40°C to +85°C SO16

.

  • DS3231MZ+ ...-45°C to +85°C SO8
  • DS3231MZ/V+ -45°C to +85°C SO8
  • DS3231M+ .... -45°C to +85°C SO16

When rated for below freezing, it means the package moisture seal is better but resonator drift will be greater at extreme temps. Therefore the same chip with 3.5ppm in the commercial range may be 5ppm in the military range ( or Winnipeg temp range ;) with the same quality

SO8 means Small Outline 8 pin. This the basic difference. There may be more if you read the spec. ..your job...

Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

Added

For context one month has 2,592,000 seconds so 3 ppm error translates to a clock error of 3parts/million *2.59million seconds/month = 7.77 seconds error per month or a frequency error of the same ratio.

Since the clock error versus Temperature is parabolic around room temp error increases in either temperature extreme.

But there are two error components to any resonator error.

  • Tolerance at Room Temp in ppm and Stability vs wide temp range. in ppm both are added to obtain expected worst case error. Room Temp tolerance can be tuned by trimmer caps.

    Chip functions

I expect but have not read specs that all chips have the same basic code functions, but you must verify.

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I found that DS3231M reads its internal temperature sensor once a second, while DS3231SN does it once ... about a minute. The step between neighboring temperature readings is 0,25 deg. by Celsius in both cases.

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