CC1310: CC1310 can't sleep during orphan state

Hi,

  I  have a problem ,I use cc1310 at 15.4 stack (simplelink cc1310 1.40 SDK)

 When the sensor disconnect its coordinator,it becomes orphan state,but its current is 3.5mA at least duaring orphan scanning ,it can't sleep to reduce the consumption,why?

Thanks!