2.1.4.1 Introduction

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The temperature variable in the SoC Products Group Designer software refers to the junction temperature, not the ambient, case, or board temperatures. This is an important distinction because dynamic and static power consumption will cause the chip's junction temperature to be higher than the ambient, case, or board temperatures. EQ 1 through EQ 3 give the relationship between thermal resistance, temperature gradient, and power.

Figure 2-3. EQ 1

Figure 2-4. EQ 2

Figure 2-5. EQ 3

where

θ_JA = Junction-to-air thermal resistance
θ_JB = Junction-to-board thermal resistance
θ_JC = Junction-to-case thermal resistance
T_J = Junction temperature
T_A = Ambient temperature
T_B = Board temperature (measured 1.0 mm away from the package edge)
T_C = Case temperature
P = Total power dissipated by the device

Table 2-6. Package Thermal Resistance
Product	θ_JA			θ_JC	θ_JB	Units
Product	Still Air	1.0 m/s	2.5 m/s	θ_JC	θ_JB	Units
A2F060¹-FG256	36.9	31.1	29.4	TBD	23.7	°C/W
A2F500-FG256	26.2	20.6	18.9	TBD	13.2	°C/W
A2F500-FG484	21.9	18.6	16.4	7.5	11	°C/W

Note:

Device A2F060 is discontinued.