ECG 497/498

Homework #1

Print this page, write in your answers (showing some work), and hand in Fri, Sept. 17.

1) Estimate the temperature rise above ambient for the following 5V regulator (with out a heatsink in still air). The load current is 100mA and the input voltage is 15V (Hint: use the Thermal Resistance Junction-Air). You may neglect the regulators quiescent current when calculating the power dissipation.

http://www.fairchildsemi.com/ds/KA%2FKA7805E.pdf

2) Estimate the temperature rise above ambient (same input and load) if the following heat sink was attached the regulator (still no airflow, Hint: use the Thermal Resistance Junction-Case + Thermal Resistance of the Heatsink).

http://www.aavidthermalloy.com/bin/stdisp.pl?Pnum=6030b-tt

3) Estimate the temperature rise if a fan was blowing 300ft/min of air across the heatsink (every thing else is the same, Hint: use the graph to find the new value for the Thermal Resistance of the heat sink).