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參數(shù)資料
| 型號(hào)： | LP3963 |
| 文件頁數(shù)： | 15/22頁 |
| 文件大?。?/td> | 479K |
| 代理商： | LP3963 |
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
output voltage. The LP3961/LP3964 use an internal MOS-
FET with an Rds(on) of 240m
(typically). For CMOS LDOs,
the dropout voltage is the product of the load current and the
Rds(on) of the internal MOSFET.
Reverse Current Path
The internal MOSFET in LP3961and LP3964 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.
Maximum Output Current Capability
LP3961 and LP3964 can deliver a continuous current of
800mA over the full operating temperature range. A heatsink
may be required depending on the maximum power dissipa-
tion 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
GND
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
J-
max
):
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
LP3961 and LP3964 are available in TO-220, TO-263, and
SOT-223 packages. The thermal resistance depends on
amount of copper area or heat sink, and on air flow. If the
maximum allowable value of
θ
calculated above is
≥
60
C/W for TO-220 package,
≥
60 C/W for TO-263 package,
and
≥
140 C/W for SOT-223 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 Packages
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
junction to the surface of the heat sink and
θ
is the thermal
resistance 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
between 1.5C/W to 2.5C/W. If the exact value is unknown,
2C/W can be assumed.
10112908
FIGURE 2. Improving remote load regulation using LP3964
L
www.national.com
15
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LP3963_03 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3A Fast Ultra Low Dropout Linear Regulators |
| LP3963_06 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3A Fast Ultra Low Dropout Linear Regulators |
| LP3963-1.8 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3A Fast Ultra Low Dropout Linear Regulators |
| LP3963ES-1.8 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3A Fast Ultra Low Dropout Linear Regulators |
| LP3963ES-1.8/NOPB | 功能描述:IC REG LDO 1.8V 3A TO-263-5 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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