RTC Current Consumption

Hi,

We have a spreadsheet to know how much RTC consumes the current. RTC power consumption is dependant to CPU speed. If CPU is idle, the normal range of RTC power consumption is 6 uA @1.3V.

Regards,

Hyun

Many Thanks. Useful information.

Can anyone clarify the power supplies on the RTC. Specifically, do we need to have BOTH Core (CV) and I/O (DV) running in order to have the RTC clocking the calendar forward? If we only run the core RTC supply and not I/O DVrtc supply, does the RTC not run, does it not do anything with Wakeup, etc? Can the RTC wake the system up if DVrtc is not being supplied?

Please clarify, if someone knows. Thanks,

Hi,

CVRTC (Core)  must be supplied even if you are not using RTC functiion.

DVRTC (IO) is required if you use teh Wake up pin or RTC CLKOUT.

Regards,

Hyun

Hyun,

OK, let me summarize my understanding and you can perhaps confirm or correct my underdstanding:

1. CVRTC must always be applied. This will power the RTC so that it can keep time, and NO other power is needed to simply keep track of time/date. So we can completely shut down the entire C5505 except for CVRTC, and we have a clock/calendar that will work continuously.

2. DVRTC is NOT required to keep time, and is only required if we want to use the wakeup or clock output features. But if all we want it timekeeping, we can shut down DVRTC.

3. If we do shut down DVRTC, there is NO WAY for the clock to wake up the CPU, but it will continue to keep time.

4. Current consumption, according to your spreadsheet, is 7uA if we only run the RTC with no I/O, and is 17uA + 7uA if we run the RTC with IO capability.

5. It seems as if we need to completely shut down all the other supplies if we want to minimize current draw. Simply placing the processor etc. in an Idle state will cause a lot more than 7uA to be drawn from the battery.

Is this correct?

hi,

1. CVRTC must always be applied. This will power the RTC so that it can keep time, and NO other power is needed to simply keep track of time/date. So we can completely shut down the entire C5505 except for CVRTC, and we have a clock/calendar that will work continuously.

--> Correct

2. DVRTC is NOT required to keep time, and is only required if we want to use the wakeup or clock output features. But if all we want it timekeeping, we can shut down DVRTC.

-->Correct

3. If we do shut down CPU, there is NO WAY for the clock to wake up the CPU, but it will continue to keep time.

--> Yes, there is a way to wake up the CPU. There is RTC Alram function to wake up CPU but not with external wake up pin.

   Note: Analog power should be supplied before wake up happens.

4. Current consumption, according to your spreadsheet, is 7uA if we only run the RTC with no I/O, and is 17uA + 7uA if we run the RTC with IO capability.

--> Yes. When you enable RTC CLKOUT (register control), it drains most curret of DVRTC. If you are not using RTC CLKOUT, DVRTC comsumes a lot less than CVRTC.

5. It seems as if we need to completely shut down all the other supplies if we want to minimize current draw. Simply placing the processor etc. in an Idle state will cause a lot more than 7uA to be drawn from the battery.

--> Correct. of course there will be a leakage curren if you supply power.

Regards,

Hyun

hi,

1. CVRTC must always be applied. This will power the RTC so that it can keep time, and NO other power is needed to simply keep track of time/date. So we can completely shut down the entire C5505 except for CVRTC, and we have a clock/calendar that will work continuously.

--> Correct

2. DVRTC is NOT required to keep time, and is only required if we want to use the wakeup or clock output features. But if all we want it timekeeping, we can shut down DVRTC.

-->Correct

3. If we do shut down CPU, there is NO WAY for the clock to wake up the CPU, but it will continue to keep time.

--> Yes, there is a way to wake up the CPU. There is RTC Alram function to wake up CPU but not with external wake up pin.

   Note: Analog power should be supplied before wake up happens.

4. Current consumption, according to your spreadsheet, is 7uA if we only run the RTC with no I/O, and is 17uA + 7uA if we run the RTC with IO capability.

--> Yes. When you enable RTC CLKOUT (register control), it drains most curret of DVRTC. If you are not using RTC CLKOUT, DVRTC comsumes a lot less than CVRTC.

5. It seems as if we need to completely shut down all the other supplies if we want to minimize current draw. Simply placing the processor etc. in an Idle state will cause a lot more than 7uA to be drawn from the battery.

--> Correct. of course there will be a leakage curren if you supply power.

Regards,

Hyun