Replacement for DS1307 RTC?
JBWolf
Posts: 405
I am working on a battery powered project.
The DS1307 RTC is great for most projects... its easy to use, low power and low cost, however the 5v requirements are an inconvenience. Also the part has been discontinued.
Is there a low cost alternative to the DS1307 that runs on 3.3v and uses i2c?
Accuracy, low power consumption and cost are priorities.
I found the DS1338 however it costs almost 5x more
Comments
These both seem to support 3.3V:
https://www.parallax.com/product/p2-rtc-add-on-board/
https://www.parallax.com/product/ds3231-at24c32-real-time-clock-module/
The P2 board can be used with any uC and is the compact & better quality "Made in USA" option, vs the cheapo commodity board. Options for all occasions!
Or if you have access to only a smidgen of Parallax products like we in the UK, I'm a fan of the Mikroe Click modules.
Craig
One of the best, from my own exerience, is the RV-3028 from Micro Crystal AG.
Draws almost no power, is vey accurate and tiny. There is a dev board for it as well, if you are afraid of it's small size to work with, and other modules too, also very convenient.
The second close would be the RV-3032.
Both may not be super cheap but well worth the money spent.
ADI still shows the DS1307 as active ? - and clones from lcsc are low cost.
It seems to pivot VPF from VBAT, so a lower VBAT may allow 3v3 operation ?
They also show a DS1308, which has wider Vcc choices, still with NV SRAM if you need that ?
Addit : PCF85263 has VBAT and fine trim
Or the newer MAX31343 has TXCO performance.
Does it need battery handling ?, If not :
The 8563 series are low cost, an multi sourced.
The PCF85063 has an offset trim register, so can get more accuracy with a single point calibrate, as does the BU5873 - these use digital trim
The JXR260 has CL trim, and seems to have a standard pinout.
Excellent options!
The RV3032 is the smallest RTC I think I have ever seen, and price isnt bad either.
The PCF's are an excellent option as well and are very lost cost!
I like them both
Agree with the RV30xx's, - wish I'd seen those sooner.
The RV-3028 has single point calibrate, at 25'C only.
The RV-3032 has a full TCXO, with temperature sense, and it has an interesting 8192 Hz to 67.109 MHz in 8192 Hz steps CLKOUT option.
It says that is not temperature compensated, but it must be at least crystal disciplined ? You cannot get N * 8192 without a form of PLL, which means the xtal is involved ?
Has anyone used the RV-3032 clock out and checked jitter and averages ?
I purchased an eval board for the RV3032 & 3028 to give it a tryout.
Here is where you can find one:
https://www.digikey.com/en/products/detail/micro-crystal-ag/RV-3032-C7-EVALUATION-BOARD/16273063
https://www.digikey.com/en/products/detail/micro-crystal-ag/RV-3028-C7-EVALUATION-BOARD/10431075
No, I do not have the right tools to measure jitter.
@JBWolf, a small hint - make sure you review carefully and understand the datasheet in section where it says about password protection. I'd suggest, for development, store it in RAM (it won't survive the total power loss but it also won't make your chip locked if you forget what you set it to).