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參數(shù)資料
| 型號： | LP2956A |
| 廠商： | National Semiconductor Corporation |
| 文件頁數(shù)： | 10/16頁 |
| 文件大小： | 501K |
| 代理商： | LP2956A |
Application Hints
HEATSINK REQUIREMENTS
A heatsink may be required with the LP2956 depending on
the maximum power dissipation and maximum ambient tem-
perature of the application. Under all expected operating
conditions, the junction temperature must be within the
range specified under Absolute Maximum Ratings.
To determine if a heatsink is required, the maximum power
dissipated by the regulator, P(max), must be calculated. It is
important to remember that if the regulator is powered from
a transformer connected to the AC line, the
maximum
specified AC input voltage
must be used (since this pro-
duces the maximum DC input voltage to the regulator). Fig-
ure 1 shows the voltages and currents which are present in
the circuit. The formula for calculating the power dissipated
in the regulator is also shown in Figure 1 (the currents and
power due to external resistive dividers are not included, and
are typically negligible).
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)
where:
T
(max) is the maximum allowable junction tem-
perature
T
A
(max) is the maximum ambient temperature
Using the calculated values for T
(max) and P(max), the re-
quired value for junction-to-ambient thermal resistance,
θ
(J-A)
, can now be found:
θ
(J-A)
= T
R
(max)/P(max)
The heatsink for the LP2956 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
shown in Table 1
TABLE 1.
Part
Package
Pins
LP2956IN
LP2956AIN
LP2956IM
LP2956AIM
Figure 2 shows copper patterns which may be used to dissi-
pate heat from the LP2956:
16-Pin Plastic DIP
16-Pin Plastic DIP
16-Pin Surface Mt.
16-Pin Surface Mt.
4, 5, 12, 13
4, 5, 12, 13
1, 8, 9, 16
1, 8, 9, 16
Table 2 shows some typical values of junction-to-ambient
thermal resistance (
θ
J-A
) for values of L and W (1 oz. cop-
per).
TABLE 2.
Package
16-Pin
Plastic
DIP
L (In.)
1
H (In.)
0.5
θ
J-A
(C/W)
70
2
3
4
6
1
2
3
6
4
2
1
60
58
66
66
83
70
67
69
71
73
1.5
0.19
0.19
0.5
1
1.5
0.19
0.19
0.19
16-Pin
Surface
Mount
EXTERNAL CAPACITORS
A 2.2 μF (or greater) capacitor is required between the main
output pin and ground to assure stability. The auxiliary output
requires 10 μF to ground. Without these capacitors, the part
may oscillate. Most types of tantalum or aluminum electrolyt-
ics will work here. Film types will work, but are more expen-
sive. Many aluminum electrolytics contain electrolytes which
freeze at 30C, which requires the use of solid tantalums
below 25C. The important characteristic of the capacitors
is an ESR of 5
(or less) on the main regulator output and an
ESR of 1
(or less) on the auxiliary regulator output (the
DS011339-9
FIGURE 1. Current/Voltage Diagram
DS011339-10
*For best results, use L = 2H
FIGURE 2. Copper Heatsink Patterns
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP2956AIM | 制造商:Texas Instruments 功能描述: |
| LP2956AIM/NOPB | 功能描述:IC REG LDO ADJ .25A 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標(biāo)準(zhǔn)）:0.28V @ 150mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:150mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應(yīng)商設(shè)備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
| LP2956AIMX | 功能描述:IC REG LDO ADJ .25A 16-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標(biāo)準(zhǔn)）:0.28V @ 150mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:150mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應(yīng)商設(shè)備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
| LP2956AIMX/NOPB | 制造商:Texas Instruments 功能描述:LDO Regulator Pos 1.23V to 29V 0.25A/0.075A 16-Pin SOIC N T/R |
| LP2956AIN/NOPB | 功能描述:IC REG LDO ADJ .25A 16-DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:4V 輸入電壓:最高 16V 電壓 - 壓降（標(biāo)準(zhǔn)）:0.28V @ 150mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:150mA 電流 - 限制（最?。?- 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:5-VFBGA 供應(yīng)商設(shè)備封裝:5-uSMD 包裝:Digi-Reel® 其它名稱:LP2985AIBP-4.0DKR |
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