37.9 Thermal Specifications

Table 37-9. Thermal Specifications
Symbol Description Typ. Unit Conditions
θJA Thermal Resistance Junction to Ambient 50 °C/W 28-pin SPDIP package (SP)
47 °C/W 28-pin SSOP (SS)
36 °C/W 28-pin VQFN (STX)
57 °C/W 32-pin TQFP package (PT)
33 °C/W 32-pin VQFN package (RXB)
TJMAX Maximum Junction Temperature Refer to the Absolute Maximum Ratings section
Note:
  • Power dissipation is calculated as PDIS = VDD × {IDD - Σ IOH} + Σ {(VDD - VOH) × IOH} + Σ (VOI × IOL)
  • Internal Power Dissipation is calculated as PINTERNAL = IDD × VDD, where IDD is current to run the chip alone without driving any load on the output pins.
  • Derated Power is calculated as PDER = PDMAX (TJ-TA)/θJA, where TA = Ambient Temperature, TJ = Junction Temperature.