NCV4276B
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14
Table 7. D
2
PAK 5-LEAD THERMAL RC NETWORK MODELS
Drain Copper Area (1 oz thick) 241 mm
2
788 mm
2
241 mm
2
788 mm
2
(SPICE Deck Format) Cauer Network Foster Network
241 mm
2
653 mm
2
Units Ta u Ta u Units
C_C1 Junction GND 1.00E−06 1.00E−06 W−s/C 1.361E−08 1.361E−08 sec
C_C2 node1 GND 1.00E−05 1.00E−05 W−s/C 7.411E−07 7.411E−07 sec
C_C3 node2 GND 6.00E−05 6.00E−05 W−s/C 1.005E−05 1.007E−05 sec
C_C4 node3 GND 1.00E−04 1.00E−04 W−s/C 3.460E−05 3.480E−05 sec
C_C5 node4 GND 2.82E−04 2.87E−04 W−s/C 7.868E−04 8.107E−04 sec
C_C6 node5 GND 5.58E−03 5.95E−03 W−s/C 7.431E−03 7.830E−03 sec
C_C7 node6 GND 4.25E−01 4.61E−01 W−s/C 2.786E+00 2.012E+00 sec
C_C8 node7 GND 9.22E−01 2.05 W−s/C 2.014E+01 2.601E+01 sec
C_C9 node8 GND 1.73 4.88 W−s/C 1.134E+02 1.218E+02 sec
C_C10 node9 GND 7.12 1.31 W−s/C sec
241 mm
2
653 mm
2
R’s R’s
R_R1 Junction node1 0.015 0.0150 C/W 0.0123 0.0123 C/W
R_R2 node1 node2 0.08 0.0800 C/W 0.0585 0.0585 C/W
R_R3 node2 node3 0.4 0.4000 C/W 0.0257 0.0260 C/W
R_R4 node3 node4 0.2 0.2000 C/W 0.3413 0.3438 C/W
R_R5 node4 node5 1.85638 1.8839 C/W 1.77 1.81 C/W
R_R6 node5 node6 1.23672 1.2272 C/W 1.54 1.52 C/W
R_R7 node6 node7 9.81541 5.3383 C/W 4.13 3.46 C/W
R_R8 node7 node8 33.1868 18.9591 C/W 6.27 5.03 C/W
R_R9 node8 node9 27.0263 13.3369 C/W 60.80 29.30 C/W
R_R10 node9 GND 1.13944 0.1191 C/W C/W
NOTE: Bold face items represent the package without the external thermal system.
The Cauer networks generally have physical
significance and may be divided between nodes to separate
thermal behavior due to one portion of the network from
another. The Foster networks, though when sorted by time
constant (as above) bear a rough correlation with the Cauer
networks, are really only convenient mathematical models.
Cauer networks can be easily implemented using circuit
simulating tools, whereas Foster networks may be more
easily implemented using mathematical tools (for instance,
in a spreadsheet program), according to the following
formula:
(eq. 6)
R(t) +
n
S
i + 1
R
i
ǒ
1−e
−tńtau
i
Ǔ
