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參數(shù)資料
| 型號(hào)： | LP3856ET-1.8 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | 3A Fast Response Ultra Low Dropout Linear Regulators |
| 中文描述： | 1.8 V FIXED POSITIVE LDO REGULATOR, 0.6 V DROPOUT, PSFM5 |
| 封裝： | TO-220, 5 PIN |
| 文件頁(yè)數(shù)： | 14/18頁(yè) |
| 文件大小： | 417K |
| 代理商： | LP3856ET-1.8 |
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Application Hints
(Continued)
remote load will provide regulation at the remote load, as
shown in
Figure 4
. If the sense option pin is not required, the
sense pin must be connected to the V
OUT
pin.
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 LP3853 and LP3856 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
LP3853 and LP3856 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
LP3853 and LP3856 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.
20030908
FIGURE 4. Improving remote load regulation using LP3856
L
www.national.com
14
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP3856ET-2.5 | 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(dòng)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 |
| LP3856ET-2.5/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(dòng)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 |
| LP3856ET-3.3 | 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(dòng)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 |
| LP3856ET-3.3/NOPB | 功能描述:低壓差穩(wěn)壓器 - LDO 3A Low Dropout Reg 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(dòng)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 |
| LP3856ET-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(dòng)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 |
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