Power Dissipation

Question

I am Using ADSP-21369,for the processor I wanted to calculate "Junction temperature @ ambient 25deg". In the datasheet "ADSP-21369 (Rev. H)" to find the Power dissipation its mentioned to refer "Engineer-to-Engineer Note EE-299", but nowhere I could find the Pd. Instead In appendix D, To calculate Tj, said to use total Power consumption of processor in the formula "Tj = Ttop + (PTOTAL x &psi;JT) 
 Please let me know the which formula to be followed to calculate TJ, Either Tj = TT + (PTOTAL x &psi;JT) or Tj= Ta + (&theta;JA &times; Pd) and Where I can find Pd for the ADSP-21369. 
 
 Regards 
 Ayyappan A

Divya.P · Accepted Answer

Hi Ayyappan, As per Application note EE-299, To determine the junction temperature of the device while on the application printed circuit board (PCB), use the following equation found in the THERMAL CHARACTERISTICS section of the data sheet: Tj = Ttop + (PTOTAL x &psi;JT) The THERMAL CHARACTERISTICS section of the data sheet also provides thermal resistance (&theta;JA) values for the 256-ball Super BGA, 208-lead MQFP and LQFP packages. Data sheet values for &theta;JA are provided for package comparison and PCB design considerations only and are not recommended for verifying TJ on an actual application PCB and you can use the PTOTAL value for PD. Regards, Divya.P)