AN1902 Freescale Semiconductor / Motorola, AN1902 Datasheet - Page 26

• Manufacturer Part Number: AN1902
• Description: Quad Flat Pack No-Lead (QFN)
• Manufacturer: Freescale Semiconductor / Motorola

AN1902/D
26
mance of the QFN package when the board is adhered to a metal housing or heat sink
and a complete thermal analysis is done. These thermal resistances help bound the
thermal problem under distinct environments.
Table 9
generated using Silicon (Si) die. There is an inverse relationship between the body
size of the package and the thermal resistances. Large packages have lower R
values. The greater the body size, the larger the exposed pad, and the more PTH vias
will fit under the exposed pad. The low R
ble of dissipating 5 Watts when the bottom surface of the board is heat sunk and there
is a 45°C junction-to-heat sink temperature difference [13].
I/O
12
12
12
16
16
16
16
20
20
20
20
24
24
24
24
32
32
32
32
32
32
Freescale Semiconductor, Inc.
For More Information On This Product,
Body Size
mm x mm
has some thermal information for certain QFN packages. All of the data was
3 x 3
3 x 3
3 x 3
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
4 x 4
5 x 5
5 x 5
5 x 5
5 x 5
7 x 7
7 x 7
Table 9 Thermal Resistances for Various QFN Packages
Quad Flat Pack No-Lead (QFN)
Go to: www.freescale.com
Pitch
0.50
0.50
0.50
0.65
0.65
0.65
0.65
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.65
0.65
mm
2.25 x 2.25
2.25 x 2.25
2.25 x 2.25
2.25 x 2.25
mm x mm
Flag Size
1.2 x 1.2
1.2 x 1.2
1.2 x 1.2
2.0 x 2.0
2.0 x 2.0
2.0 x 2.0
2.0 x 2.0
2.1 x 2.1
2.1 x 2.1
2.1 x 2.1
2.1 x 2.1
3.1 x 3.1
3.1 x 3.1
3.1 x 3.1
3.1 x 3.1
4.7 x 4.7
4.7 x 4.7
0.56 x 0.56
0.56 x 0.56
0.95 x 0.95
0.56 x 0.56
1.05 x 1.05
0.56 x 0.56
1.35 x 1.35
1.85 x 1.85
0.56 x 0.56
2.16 x 2.16
mm x mm
Die Size
0.3 x 0.3
0.8 x 0.8
1.1 x 1.1
1.6 x 1.6
1.2 x 1.2
1.7 x 1.7
1.2 x 1.2
2.2 x 2.2
2.7 x 2.7
2.9 x 2.9
3.8 x 3.8
θJC
values indicate that this package is capa-
R
°C/W
θJA
277
230
213
196
173
168
157
179
154
150
140
178
150
147
139
154
108
116
111
96
90
1,2
R
θJMA
°C/W
152
102
85
79
56
52
46
78
53
50
44
79
50
48
43
71
34
32
32
30
27
1,3
R
°C/W
122
θJB
72
56
57
34
30
23
56
30
27
22
58
29
27
22
52
15
13
13
13
10
MOTOROLA
4
R
°C/W
θJMA
3.4
2.3
2.0
3.5
1.2
θJC
97
41
21
39
16
12
40
13
11
40
11
39
6
6
9
5
5