OMAP-L138 / AM1808 RTC SPLITPOWER?

Mike,

How are you measuring the RTC power consumption?  20uW is when RTC_CVDD is powered on and the other power rails are powered off.  If all the power rails are powered on, you should see power in the mW range.

--Christina

I am only appying power to the RTC_CVDD.  All other rails are off.  Can you tell me the difference between power draw when the RTC CTRL.SPLITPOWER is 0 vs 1?

-Mike

Mike,

The typical power difference between SPLITPOWER 0 vs 1 is unknkown.  The bit is permanently tied high on silicon revision 2.0 and beyond so we shouldn't have to worry too much about that.  Can you check to make sure that the normal CVDD 1.2V supply is actively driven or pulled to GND and is not left floating?

-Tommy

I think that with this test CVDD may be floating.  What impedence to ground is required?  

-Mike

I'm also using rev 1 silicon, so does this mean that I shouldn't bother trying to make power measurements?

Mike,

For proper power isolation, the CVDD supply needs to be biased to ground, not floating.  You can still take valid power measurements with silicon revision 1.x, but you just need to initialize the RTC first so that the SPLITPOWER bit is set.

-Tommy

OK.  I'm sort of back to my original problem.  It looks like the linux rtc driver in the SDK is setting the SPLITPOWER bit to 0 (the code does a read modify write, but the SPLITPOWER bit appears to be read only, and always reads back to zero on rev 1 silicon).  I will modify the kernel to ensure that the bit gets set.  Thanks.