RCM6750 Backup battery drain

Question

Hello,

I know this topic has been covered before but here's another twist to the story: When powered down the current draw on the battery is about 42uA - which closely matches the 50uA specified in the documentation. However, when power is applied the draw goes up to 5mA draining the battery in a matter of a few days.
I went through all the procedures found on related bulletin boards or FAQs to lower the current draw and tried brand new RCMs to no avail.
As expected, the current draw from the battery is 0A without the controller installed.

Thanks for any hints or ideas!
Martin

Answer 1

Can you provide details on how you've interfaced the RCM6750 to your carrier board? If you connect a battery to the VBAT pin of an RCM6700 Minicore Development board, do you see a similar draw?

Comments

Thanks for the idea Tom! I'll give it a try and will let you know the result.

Answer 2

Hello Martin,

Two suggestions.

The first version of the 6000 processor had a much higher current draw. Check to see if the processor version is A or B.

Second, this might be a sequencing issue between applying the battery and the power connector. The RCM6700 user manual in "Appendix G: Power Supply" covers the sequencing of how the battery and mains power should be applied.

Comments

One more suggestion.  Please check that the power supply voltage has not dropped. This can cause significant drain on the battery if the power supply voltage is not maintained.