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ADP198 Reverse Current Blocking?

Question asked by Hasse on May 29, 2013
Latest reply on Feb 7, 2015 by Lionelwallace


I just received the first PCBs for a new small measuring device. I am using the ADP198ACBZ-R7 in a circuit identical to the one published in the ADP198 datasheet rev.E on page 15.  The voltage source V2 is in my case a 3V button cell. This simple circuit just does not work as one would expect. If the AC supply is first connected and then the button cell is inserted into it's holder, the circuit seems to function. When disconnecting the AC power, the button cell takes over the load seamlessly.  Fine so far. But when the AC power returns I have lots of current flowing backwards into my button cell !  The reverse current (between 80 - 160mA) will quickly destroy the cell. If (with AC on) I cut the trace between Vin and EN the reverse current stops. It now remains blocked even if I re-connect EN to Vin.  Then, when disconnecting the AC and re-connecting it the reverse current starts.  I have 3 PCBs that all behave the same way. Have Analog Devices tested this circuit? What can possibly be wrong?