Datasheet

0 3 6 9 12 15
75
85
95
105
115
125
MAX. AMBIENT TEMPERATURE (°C)
I
OUT
(A)
2 3 4 5 6 7 8 9 10
10
12
14
16
18
20
22
24
26
28
30
THERMAL RESISTANCE (
JA
)
BOARD AREA (in
2
)
LM21215A
www.ti.com SNOSB87B –MARCH 2011–REVISED MARCH 2013
Figure 37, shown below, provides a better approximation of the θ
JA
for a given PCB copper area. The PCB used
in this test consisted of 4 layers: 1oz. copper was used for the internal layers while the external layers were
plated to 2oz. copper weight. To provide an optimal thermal connection, a 3 x 4 array of 8 mil. vias under the
thermal pad were used, and an additional sixteen 8 mil. vias under the rest of the device were used to connect
the 4 layers.
Figure 37. Thermal Resistance vs PCB Area (4 Layer Board)
Figure 38 shows a plot of the maximum ambient temperature vs. output current for the typical application circuit
shown in Figure 40, assuming a θ
JA
value of 24 °C/W.
Figure 38. Maximum Ambient Temperature vs. Output Current (0 LFM)
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