ISL78841ASxH VDD maximum rating

Question

Hello, 
 
 The datasheet for this device under the absolute maximum ratings states: 
 Supply Voltage VDD Without BEAM ...(GND-0.3V) to +30.0V 
 Supply Voltage VDD Under Beam .....(GND-0.3V) to 14.7V 
 
 What does "BEAM" mean? 
 
 Thanks 
 hmee

Cindy H · Answer

The term "without beam" refers to an environment without heavy ions versus "under beam" which refers to a an environment under heavy ions. We determine this during SEE and specifically SEL (Single Event Latch-up) and SEB (Single Event Burnout) testing. 
 The maximum operational voltage when not under beam is typically a safe voltage below the voltage breakdown of the device. 
 The maximum operational voltage when under beam is the safe voltage in a heavy ion environment so that SEL and SEB will not occur. 
 The maximum operating voltage under beam is always less than when not under a heavy ion environment. We make this distinction to allow for de-rating decisions made by system designers. 
 Best regards, Cindy, Renesas Online Apps Engineer