hi 

      I would like to use RTC component of PSOC3 to implement the time and date.... i am using CY8CKIT-030,in which a 32.768KHZ ECO already exists..............now i am using USB connector to power on my kit....but, after completion of my design i am planning to use 9V/12V power adaptor to give power supply to my kit.....

 From a few  documents i red that there are four different power modes are available (ACTIVE, ALTERNATE ACTIVE, SLEEP and HIBERNATE) but, all the four power modes requires a continuous power supply and depending on the mode the amount of power consumption may vary......

If i give powersupply  from AC 220V, mains supply (with the help of 9V/12V DC adaptor)....i could give it whenever i am in need to utilize the device......i could'nt give the power continuously (many of the interrupts may expect from Indian electricity board)........then how my RTC clock internally run, and how it will give the correct time when i turned it On after some time.....

do i need to use additional battery back up for RTC?

previously, when i was working with PSOC1, i did the same..... i interfaced DS1307, to which i have given 3.3v  backup power from LI cell......and i have drawn 5V DC supply from 220 AC (with the help of regulators) and utilized these 5V supply to run the entire designed system..

can any one help me how to run  RTC continuously, even after the system turned off.

When you use the PSOC-internal RTC for keeping time, you need to ensure that the PSoC runs continously. You can do this by adding a backup battery - but then you should make sure the PSoC runs in sleep mode to ensure long battery life.

Another option is to use an external RTC, and back this up with a battery (or maybe only a large capacitor). For example the PCF2129A from NXP draw only 650nA in backup mode, and is internally temperature-compensated. It should last several weeks from a 1000µF capacitor. This might be a better option since it is more accurate, and doesnÄt need power management in the PSoC.

Use a super capacitor -

http://en.wikipedia.org/wiki/Electric_double-layer_capacitor

http://en.wikipedia.org/wiki/Electric_double-layer_capacitor

Regards, Dana.

Obviously two capacitors are better than one (broad smile)

Bob

Application info -

http://www.edn.com/file/18347-268379.pdf

Regards, Dana.

http://www.cypress.com/?id=4&rID=51941 -> Refer to this KB article. If you want to calculate the value of Capacitor you want to use to run RTC even when the power supply if OFF, you need to know the following parameters:

1. What is the duration of time for which main power supply will be OFF?

2. What is the power consumption of the device during active & during sleep modes?

3. How much time does it take for you to detect the failure of main supply and move onto low power mode?

4. Based on the above points, you can calculate the average current you need to provide the device for continuous operation. Also find out the peak current required. Calculate the value of Capacitor which can provide this peak current and has the enough amount of energy stored in it.

But be aware that when using a super cap, its leakage current might be higher that the current needed by the RTC (several microamps are not uncommon for larger caps). Also, there caps often have a rather high impedance and can be used only with small currents (I have one at home which is rated only for 10 microamps and has an internal resistance of 1k).

There are super caps with mOhm ESR, and low uA self discharge.

Some reference material -

http://www.glyn.co.nz/downloads/documents/Maxwell/ultracap_product_guide.pdf

A calculator

http://www.maximintegrated.com/design/tools/calculators/product-design/supercap.cfm

So in short Q = CV, I = C * dV/dT, use this equation to get a size of C needed. I is sum

of PSOC sleep and capacitor self discharge. Hot values generally worst case. dT is how long

you want cap to sustain PSOC in sleep. C is a f(V) and a f(T), so use min value in your

calculations as worst case on the bacvkup side. Max value for when you are charging C.

dV is fully charged - PSOC min operating V in sleep.

The other issue is calculating how long it will take in your circuit to charge the super cap.

Panasonic, NEC-Tokin, Cooper, Maxwell vendors.

Regards, Dana.

Oh, I know that they exist. It's just something you need to check beforehand.

But OTOH, it might be simpler to just connect a CR2032 or so to the battery input of the RTC - no hassle with charging and it will last several years.