TPS786_15 Datasheet, PDF (19/37 Pages) Texas Instruments – TPS786 Ultralow-Noise, High-PSRR, Fast, RF, 1.5-A Low-Dropout Linear Regulators

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Power Dissipation (continued)
TPS786
SLVS389M – SEPTEMBER 2002 – REVISED SEPTEMBER 2015
NOTE
Both T_T and T_B can be measured on actual application boards using a thermo-gun (an
infrared thermometer).
For more information about measuring T_T and T_B, see the application note SBVA025, Using New Thermal
Metrics, available for download at www.ti.com.
By looking at Figure 33, the new thermal metrics (Ψ_JT and Ψ_JB) have very little dependency on board size. That
is, using Ψ_JT or Ψ_JB with Equation 6 is a good way to estimate T_J by simply measuring T_T or T_B, regardless of the
application board size.
35
30
DCQ
25
DRB ^YJB
KTT
20
15
10
5 ^{DCQ Y}JT
DRB Y_JT
KTT Y_JT
0
0 1 2 3 4 5 6 7 8 9 10
Board Copper Area (in²)
Figure 33. Ψ_JT and Ψ_JB vs Board Size
For a more detailed discussion of why TI does not recommend using θ_JC(top) to determine thermal characteristics,
see application report Using New Thermal Metrics, SBVA025, available for download at www.ti.com. For further
information, see application report IC Package Thermal Metrics, SPRA953, also available on the TI website.
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