The layout of the MOSFET is very important as it will be the main power switch and may therefore be required to dissipate a substantial amount of power. An incorrect layout may result in the MOSFET overheating and damage or destruction. The expected worst case power should be calculated before when selecting the TIMER capacitor. Using this data and power/thermal derating data from the datasheet, a safe maximum temperature should be designed for worst case conditions. Additional heatsinks should be used where necessary.