Operational DMD temperature and landed duty cycle interact to affect DMD usable life, and this interaction can be exploited to reduce the impact that an asymmetrical landed duty cycle has on the DMD usable life. This is quantified in the de-rating curve shown in Figure 6-1. The importance of this curve is that:

• All points along this curve represent the same usable life.
• All points above this curve represent lower usable life (and the further away from the curve, the lower the usable life).
• All points below this curve represent higher usable life (and the further away from the curve, the higher the usable life).

In practice, this curve specifies the maximum operating DMD temperature at a given long-term average landed duty cycle.