參數(shù)資料
型號: LP2952I-3.3
廠商: National Semiconductor Corporation
元件分類: 基準電壓源/電流源
英文描述: Adjustable Micropower Low-Dropout Voltage Regulators
中文描述: 可調微功率低壓差穩(wěn)壓器
文件頁數(shù): 13/22頁
文件大?。?/td> 1050K
代理商: LP2952I-3.3
Application Hints
(Continued)
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
R
(max). This is calculated
by using the formula:
T
R
(max) = T
J
(max) T
A
(max)
θ
(J–A)
= T
R
(max)/P(max)
where: T
(max)
is
the
maximum
temperature
T
A
(max) is the maximum ambient temperature
Using the calculated values for T
R
(max) and P(max), the
required value for junction-to-ambient thermal resistance,
θ
(J–A)
, can now be found:
The heatsink is made using the PC board copper. The heat
is conducted from the die, through the lead frame (inside the
part), and out the pins which are soldered to the PC board.
The pins used for heat conduction are given in
Table 1
.
allowable
junction
TABLE 1. Heat Conducting Pins
Part
Package
14-Pin DIP
Pins
3, 4, 5,
10, 11, 12
LP2952IN, LP2952AIN,
LP2952IN-3.3,
LP2952AIN-3.3
LP2953IN, LP2953AIN,
LP2953IN-3.3,
LP2953AIN-3.3
LP2952IM, LP2952AIM,
LP2952IM-3.3,
LP2952AIM-3.3,
LP2953IM, LP2953AIM,
LP2953IM-3.3,
LP2953AIM-3.3
16-Pin DIP
4, 5, 12, 13
16-Pin Surface
Mount
1, 8, 9, 16
Figure 2
shows copper patterns which may be used to
dissipate heat from the LP2952 and LP2953.
Table 2
shows
some values of junction-to-ambient thermal resistance (
θ
J–A
)
for values of L and W for 1 oz. copper.
TABLE 2. Thermal Resistance for Various Copper
Heatsink Patterns
Package
16-Pin DIP
L (in.)
1
2
3
4
6
1
2
3
1
2
3
6
4
2
H (in.)
0.5
1
1.5
0.19
0.19
0.5
1
1.5
0.5
1
1.5
0.19
0.19
0.19
θ
J–A
(C/W)
70
60
58
66
66
65
51
49
83
70
67
69
71
73
14-Pin DIP
Surface Mount
HEATSINK REQUIREMENTS (Military Temperature
Range Devices)
The
maximum
allowable
LP2953AMJ is limited by the maximum junction temperature
(+150C) and the two parameters that determine how quickly
heat flows away from the die:
the ambient temperature and
the junction-to-ambient thermal resistance of the part
.
power
dissipation
for
the
01112707
FIGURE 1. P
= (V
V
) I
L
+ (V
IN
) I
G
Current/Voltage Diagram
01112708
* For best results, use L = 2H
** 14-Pin DIP is similar, refer to
Table 1
for pins designated for
heatsinking.
FIGURE 2. Copper Heatsink Patterns
L
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PDF描述
LP2954A 5V and Adjustable Micropower Low-Dropout Voltage Regulators
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