Datasheet

0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9 10
ψ
JB
(RGW)
ψ
JB
(RGT)
ψ
JT
(RGW)ψ
JT
(RGT)
Board Copper Area (inch
2
)
ψ
JT
and ψ
JB
(°C/W)
G801
T onPCB
B
T on ofICtop
T
1mm
(a)ExampleRGW(QFN)PackageMeasurement
TPS7A7100
SBVS189E –MARCH 2012–REVISED SEPTEMBER 2013 www.ti.com
Figure 42. Measuring Points for T
T
and T
B
By looking at Figure 43, 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 3 is a good way to estimate T
J
by simply measuring T
T
or T
B
, regardless of the
application board size.
Figure 43. 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,
refer to Application Report SBVA025, Using New Thermal Metrics, available for download at www.ti.com. For
further information, refer to Application Report SPRA953, IC Package Thermal Metrics, also available on the TI
website.
20 Submit Documentation Feedback Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: TPS7A7100