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參數(shù)資料
| 型號： | LP3873ESX-3.3 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | 3A Fast Ultra Low Dropout Linear Regulators |
| 中文描述： | 3.3 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PSSO5 |
| 封裝： | TO-263, 5 PIN |
| 文件頁數(shù)： | 14/16頁 |
| 文件大?。?/td> | 365K |
| 代理商： | LP3873ESX-3.3 |
Application Hints
(Continued)
SHUTDOWN OPERATION
A CMOS Logic level signal at the shutdown ( SD) pin will
turn-off the regulator. Pin SD must be actively terminated
through a 10k
pull-up resistor for a proper operation. If this
pin is driven from a source that actively pulls high and low
(such as a CMOS rail to rail comparator), the pull-up resistor
is not required. This pin must be tied to Vin if not used.
DROPOUT VOLTAGE
The dropout voltage of a regulator is defined as the minimum
input-to-output differential required to stay within 2% of the
nominal output voltage. For CMOS LDOs, the dropout volt-
age is the product of the load current and the Rds(on) of the
internal MOSFET.
REVERSE CURRENT PATH
The internal MOSFET in LP3873 and LP3876 has an inher-
ent parasitic diode. During normal operation, the input volt-
age is higher than the output voltage and the parasitic diode
is reverse biased. However, if the output is pulled above the
input in an application, then current flows from the output to
the input as the parasitic diode gets forward biased. The
output can be pulled above the input as long as the current
in the parasitic diode is limited to 200mA continuous and 1A
peak.
POWER DISSIPATION/HEATSINKING
LP3873 and LP3876 can deliver a continuous current of 3A
over the full operating temperature range. A heatsink may be
required depending on the maximum power dissipation and
maximum ambient temperature of the application. Under all
possible conditions, the junction temperature must be within
the range specified under operating conditions. The total
power dissipation of the device is given by:
P
D
= (V
IN
V
OUT
)I
OUT
+ (V
IN
)I
GND
where I
is the operating ground current of the device
(specified under Electrical Characteristics).
The maximum allowable temperature rise (T
Rmax
) depends
on the maximum ambient temperature (T
cation, and the maximum allowable junction temperature
(T
Jmax
):
T
Rmax
= T
Jmax
T
Amax
The maximum allowable value for junction to ambient Ther-
mal Resistance,
θ
JA
, can be calculated using the formula:
θ
JA
= T
Rmax
/ P
D
LP3873 and LP3876 are available in TO-220 and TO-263
packages. The thermal resistance depends on amount of
copper area or heat sink, and on air flow. If the maximum
allowable value of
θ
JA
calculated above is
≥
60 C/W for
TO-220 package and
≥
60 C/W for TO-263 package no
heatsink is needed since the package can dissipate enough
heat to satisfy these requirements. If the value for allowable
θ
JA
falls below these limits, a heat sink is required.
HEATSINKING TO-220 PACKAGE
The thermal resistance of a TO220 package can be reduced
by attaching it to a heat sink or a copper plane on a PC
board. If a copper plane is to be used, the values of
θ
JA
will
be same as shown in next section for TO263 package.
The heatsink to be used in the application should have a
heatsink to ambient thermal resistance,
θ
HA
≤ θ
JA
θ
CH
θ
JC
.
In this equation,
θ
is the thermal resistance from the case
to the surface of the heat sink and
θ
is the thermal resis-
tance from the junction to the surface of the case.
θ
JC
is
about 3C/W for a TO220 package. The value for
θ
CH
de-
pends on method of attachment, insulator, etc.
θ
varies
between 1.5C/W to 2.5C/W. If the exact value is unknown,
2C/W can be assumed.
HEATSINKING TO-263 PACKAGE
The TO-263 package uses the copper plane on the PCB as
a heatsink. The tab of these packages are soldered to the
copper plane for heat sinking.
Figure 3
shows a curve for the
θ
JA
of TO-263 package for different copper area sizes, using
a typical PCB with 1 ounce copper and no solder mask over
the copper area for heat sinking.
As shown in the figure, increasing the copper area beyond 1
square inch produces very little improvement. The minimum
value for
θ
JA
for the TO-263 package mounted to a PCB is
32C/W.
Figure 4
shows the maximum allowable power dissipation
for TO-263 packages for different ambient temperatures,
assuming
θ
is 35C/W and the maximum junction tempera-
ture is 125C.
20060532
FIGURE 3.
θ
JA
vs Copper (1 Ounce) Area for TO-263
package
20060533
FIGURE 4. Maximum power dissipation vs ambient
temperature for TO-263 package
L
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14
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP3873ESX-5.0 | 功能描述:低壓差穩(wěn)壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| LP3873ESX-5.0/NOPB | 功能描述:低壓差穩(wěn)壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| LP3873ET-1.8 | 制造商:Texas Instruments 功能描述:V REG LDO 3A 1.8V 3873 TO-220-5 |
| LP3873ET-1.8/LB02 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LP3873ET-1.8/NOPB | 功能描述:IC REG LDO 1.8V 3A TO220-5 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?fù)浣Y(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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