A cheap RTC with integrated crystal

[ali_asadzadeh]

Hi
There are many solutions out there,But I need something with these capabilities
A RTC chip with integrated crystal in it and should  have a serial interface like I2C or SPI,have a small package and should be under 0.6USD at 1K QTY. also having internal RAM would be nice too

I fall in love with M41T62 from ST,the only problem is it's price. Do we have cheaper alternatives? where is china in this market?

[lm3baker]

I don't know of cheap ones with a built-in crystal (this seems to come with a price premium), but most of the ones with crystals are $1.50+
I did spot the NXP PCF2129 at 1.42/ 2000qty from digikey, and also found DS3231 from maxim, but being maxim it costs an arm and a leg ($5 per 1000 or so). [ edit: Maxim has quite a few see https://para.maximintegrated.com/en/results.mvp?fam=rtc ] Microchip and Rohm don't appear to have the built-in osc type RTC.

As for the Chinese options, a quick search gives me the JYRTC-1 http://www.jingyuan.com/UploadDrivers/201371155141119.pdf, website http://www.jingyuan.com/Showpro.asp?id=68&biaoming=product5, info in English http://tongfangguoxin.manufacturer.globalsources.com/si/6008849732923/pdtl/Crystal-oscillator/1132629984/Real-Time-Clock-Module.htm but I don't have a price on that.

I have used in the past some very cheap, low power (<<500nA) devices from NXP in the past (runs for months off the 3.3V 1F cap ), but they need crystals.
As an aside, it looks like RTCCs have improved a little bit over the last few years (lower currents, SRAM/NVRAM persistent storages).

[Pjotr]

All depends on accuracy. The integrated ones have a premium here, but at a price. If accuracy is not a major issue, a separate crystal stays cheapest. Epson has also some integrated ones.

[Fungus]

A RTC chip with integrated crystal in it and should  have a serial interface like I2C or SPI,have a small package and should be under 0.6USD at 1K QTY. also having internal RAM would be nice too

Yep, embedding a crystal into a chip is expensive.

Why does it have to be internal though? Crystals are cheap/small.

[rdl]

The ones with internal crystals can be temperature compensated and factory adjusted for accuracy. Using an external crystal it takes a bit of effort to get better than +/- a couple of minutes a month. Something like a DS3231 is specified for +/- a couple of ppm as supplied, which is just a few seconds per month.





edit: removed extra word

[ali_asadzadeh]

Thanks for your help. embedded crystals bring accuracy, The question is why these chips are priced higher than a MCU with lots of capabilities including a RTC!, Maybe chines friends have something cool for us.