37.9 Thermal Specifications

Table 37-9. Thermal Specifications
Symbol	Description	Typ.	Unit	Conditions
θ_JA	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)
T_JMAX	Maximum Junction Temperature			Refer to the Absolute Maximum Ratings section
Note: Power dissipation is calculated as 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.