Recall, do I that the RTC/SRAM backup battery should have a resistor in series. Two questions on this that apply to both the Domino and the Panda II. I ask because I need to squeeze as much life as possible out of the backup batteries.
First what size resistor? I’m using a 15K and measuring a 70 microamp current draw on the Domino, but a 130 microamp current draw on the Panda II.
Second question is are these typical current draws for battery backup on a FEZ? I think the LPC2388 and LPC2387 data sheets imply that the RTC needs about 20 microamps. I don’t see a spec for the SRAM.
As always, thanks for any insights you can provide.
In answer to my own question I contacted NXP since it didn’t look like the TINYCLR Forum was generating a lot of results. If anyone has a similar problem or need to know the is an errata on the LPC 2388 regarding current draw on VBat. You can access it at:
[url]http://ics.nxp.com/support/documents/microcontrollers/pdf/errata.lpc2388.pdf[/url]
There is also a work around. I can answer questions about how I solved it if needed.