38.4.6 Thermal Characteristics

Table 38-9. Thermal Characteristics
Symbol	Description	Typ.	Units	Conditions
θ_JA	Thermal Resistance Junction to Ambient (Thermal simulation, no airflow)	57.096	°C/W	28-pin SPDIP package (SP)
		45.996	°C/W	28-pin SOIC package (SO)
		54.496	°C/W	28-pin SSOP package (SS)
		36.548	°C/W	28-pin VQFN package (STX)
		33.61	°C/W	32-pin VQFN package (RXB)
		53.221	°C/W	32-pin TQFP package (PT)
Note: Power dissipation is calculated like this: P_DIS = V_DD × {I_DD - Σ I_OH} + Σ {(V_DD - V_OH) × I_OH} + Σ (V_OI × I_OL) Internal Power Dissipation is calculated as: P_INTERNAL = I_DD × V_DD, where I_DD is current to run the chip alone without driving any load on the output pins. Derated Power is calculated as: P_DER = PD_MAX (T_J-T_A)/θ_JA, where T_A = Ambient Temperature, T_J = Junction Temperature.