ncv8508b ON Semiconductor, ncv8508b Datasheet - Page 11

• Manufacturer Part Number: ncv8508b
• Description: Ncv8508b 5.0 V, 250 Ma Ldo With Watchdog And Reset
• Manufacturer: ON Semiconductor

NOTE:
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:
Table 1. SOIC 8−Lead EP Thermal RC Network Models
The Cauer networks generally have physical significance and may be divided between nodes to separate thermal behavior
10
10
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
Bold face items in the Cauer network above, represent the package without the external thermal system. The Bold face items in
the Foster network are computed by the square root of time constant R(t) = 225 * sqrt(time(sec)). The constant is derived based
on the active area of the device with silicon and epoxy at the interface of the heat generation.
2.7E−06
1.1E−05
3.2E−05
1.3E−04
1.8E−03
7.9E−03
2.5E−02
1.4E−01
4.1E−01
1.6E+00
54 mm
21.431
40.130
23.392
24.381
0.474
1.086
5.883
1.944
4.655
3.011
C’s
R’s
2
Cauer Network
717 mm
2.7E−06
1.1E−05
3.2E−05
1.3E−04
1.8E−03
8.3E−03
3.1E−02
5.1E−01
2.1E+00
6.3E+01
15.678
18.454
0.474
1.086
3.010
5.874
1.911
4.264
9.238
3.581
C’s
R’s
2
R(t) +
http://onsemi.com
i + 1
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
W−s/C
S
Units
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
n
R i 1−e −t tau i
11
4.00E+00
1.16E+01
5.58E+01
1.00E−06
1.00E−05
1.00E−04
9.39E−04
3.13E−03
3.30E−02
6.00E−01
54 mm
15.000
11.494
34.982
50.566
0.282
0.610
1.929
5.825
2.700
3.000
Tau
R’s
2
Foster Network
1.00E−06
1.00E−05
1.00E−04
9.39E−04
3.13E−03
3.30E−02
6.00E−01
4.00E+00
4.83E+01
2.37E+02
717 mm
15.000
20.473
0.282
0.610
1.929
5.825
2.700
3.000
7.797
5.953
Tau
R’s
2
Cu Area
units
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
C/W
sec
sec
sec
sec
sec
sec
sec
sec
sec
sec