TPS706_15 Datasheet, PDF (17/31 Pages) Texas Instruments – TPS706 150-mA, 6.5-V, 1-μA IQ Voltage Regulators with Enable

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TPS706
SBVS245A – OCTOBER 2014 – REVISED MARCH 2015
Layout Guidelines (continued)
Estimating the junction temperature can be done by using the thermal metrics Ψ_JT and Ψ_JB, shown in the
Thermal Information. These metrics are a more accurate representation of the heat transfer characteristics of the
die and the package than R_θJA. The junction temperature can be estimated with Equation 2.
Y_JT:
T
J
=
T
T
+
Y_JT
·
P
D
Y_JB:
T
J
=
T
B
+
Y_JB
·
P
D
where:
• P_D is the power dissipation shown by Equation 1,
• T_T is the temperature at the center-top of the IC package,
• T_B is the PCB temperature measured 1 mm away from the IC package on the PCB surface.
(2)
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 Using New Thermal Metrics
(SBVA025), available for download at www.ti.com.
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