Are you sure this is not just a scoping issue? Are you using controller-as syntax? If I remember correctly, a lot of the ui-boostrap directives create an isolate scope, so if you're trying to reference a scope variable for your config object to pass in to the AmCharts directive, the $scope variable in the view could be referencing that isolate scope from the ui-boostrap tab instead of the parent scope you think you're referencing. This is more than likely your problem.
Are you sure this is not just a scoping issue? Are you using controller-as syntax? If I remember correctly, a lot of the ui-boostrap directives create an isolate scope, so if you're trying to reference a scope variable for your config object to pass in to the AmCharts directive, the $scope variable in the view could be referencing that isolate scope from the ui-boostrap tab instead of the parent scope you think you're referencing. This is more than likely your problem.
If it isnt, create a fiddle please.