TPS75515 Datasheet, PDF (17/23 Pages) Texas Instruments – FAST-TRANSIENT RESPONSE 5-A LOW-DROPOUT VOLTAGE REGULATORS

TPS75515, TPS75518, TPS75525, TPS75533 WITH POWER GOOD AND
TPS75501 FAST-TRANSIENT RESPONSE 5-A LOW-DROPOUT
VOLTAGE REGULATORS
SLVS293D – NOVEMBER 2000 – REVISED MAY 2002
THERMAL INFORMATION
TO–263 power dissipation
The TO–263 package provides an effective means of managing power dissipation in surface mount
applications. The TO–263 package dimensions are provided in the Mechanical Data section at the end of the
data sheet. The addition of a copper plane directly underneath the TO–263 package enhances the thermal
performance of the package.
To illustrate, the TPS75525 in a TO–263 package was chosen. For this example, the average input voltage is
3.3 V, the output voltage is 2.5 V, the average output current is 3 A, the ambient temperature 55°C, the air flow
is 150 LFM, and the operating environment is the same as documented below. Neglecting the quiescent current,
the maximum average power is:
P_Dmax + (3.3 – 2.5) V x 3 A + 2.4 W
(7)
Substituting T_Jmax for T_J into equation 4 gives equation 8:
R_θJAmax + (125 – 55)°Cń2.4 W + 29°CńW
(8)
From Figure 25, R_θJA vs Copper Heatsink Area, the ground plane needs to be 2 cm² for the part to dissipate
2.4 W. The model operating environment used in the computer model to construct Figure 25 consisted of a
standard JEDEC High-K board (2S2P) with a 1 oz. internal copper plane and ground plane. The package is
soldered to a 2 oz. copper pad. The pad is tied through thermal vias to the 1 oz. ground plane. Figure 26 shows
the side view of the operating environment used in the computer model.
THERMAL RESISTANCE
vs
COPPER HEATSINK AREA
40
No Air Flow
35
150 LFM
30
250 LFM
25
20
15
0
0.01
0.1
1
10
100
Copper Heatsink Area – cm2
Figure 25
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