Google AdMob plugin for Cordova, App is closing when we are clicking on the Add and press back button to return to the App

I am using Cordova frame work to build an app,I had used Google AdMob plugin for Cordova to show the Adds in my App, and My problem is when user click on any add and tries to come back to the App by clicking back button the App was closing and the user has to start it from the beginning, what i need to do to over come this issue , Thanks in Advance...