Richard Parker

Reset failure when battery backed

Discussion created by Richard Parker on Jan 5, 2012
Latest reply on Jan 8, 2012 by TomE

We are using a MCF52259 micro ccontroller with a rechargable battery connected to the VSTBY pin to maintain the Real Time Clock when the system is powered down.


With the battery connected, when the unit is turned on the system fails to start (RSTO is held low). In this fault condition if the battery supply is disconnected even temporarily the system will start running normally. The battery voltage to the VSTBY pin is currently 3.1V - well within the specified operating range of 1.8 - 3.5V.


If the unit is powered up with the battery supply disconnected (VSTBY connected to VCC) the system works correctly.


I have searched the forums and the processor User Manual and nothing sheds any light on this issue.