100

75

50

25

0

2

3

5

125

150

7

8

1

4

6

0.3

Natural Convection

50ft/min

250ft/min

300ft/min

100ft/min

150ft/min

200ft/min

CopperHeatsinkArea - cm

2

TPS70445, TPS70448

TPS70451, TPS70458

TPS70402

www.ti.com

SLVS307F – SEPTEMBER 2000 – REVISED APRIL 2010

The thermal pad is directly connected to the substrate of the IC, which for the TPS704xx series is a secondary

electrical connection to device ground. The heat-sink surface that is added to the PWP can be a ground plane or

left electrically isolated. In TO220-type surface-mount packages, the thermal connection is also the primary

electrical connection for a given terminal which is not always ground. The PWP package provides up to 24

independent leads that can be used as inputs and outputs (Note: leads 1, 12, 13, and 24 are internally

connected to the thermal pad and the IC substrate).

THERMAL RESISTANCE

vs COPPER HEATSINK AREA

Figure 34.

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