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參數(shù)資料
| 型號(hào)： | LP5951MF-2.0 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Micropower, 150mA Low-Dropout CMOS Voltage Regulator |
| 中文描述： | 2 V FIXED POSITIVE LDO REGULATOR, 0.35 V DROPOUT, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁(yè)數(shù)： | 8/10頁(yè) |
| 文件大小： | 608K |
| 代理商： | LP5951MF-2.0 |
Application Hints
POWER DISSIPATION AND DEVICE OPERATION
The permissible power dissipation for any package is a
measure of the capability of the device to pass heat from the
power source, the junctions of the IC, to the ultimate heat
sink, the ambient environment. Thus the power dissipation is
dependent on the ambient temperature and the thermal
resistance across the various interfaces between the die and
ambient air.
As stated in (Note 5) in the electrical specification section,
the allowable power dissipation for the device in a given
package can be calculated using the equation:
P
D
= (T
J(MAX)
- T
A
) /
θ
JA
With a
θ
JA
= 220C/W, the device in the SOT23-5 package
returns a value of 454 mW with a maximum junction tem-
perature of 125C at T
A
of 25C.
The actual power dissipation across the device can be esti-
mated by the following equation:
P
D
≈
(V
IN
- V
OUT
) * I
OUT
This establishes the relationship between the power dissipa-
tion allowed due to thermal consideration, the voltage drop
across the device, and the continuous current capability of
the device. These two equations should be used to deter-
mine the optimum operating conditions for the device in the
application.
EXTERNAL CAPACITORS
As is common with most regulators, the LP5951 requires
external capacitors to ensure stable operation. The LP5951
is specifically designed for portable applications requiring
minimum board space and the smallest size components.
These capacitors must be correctly selected for good perfor-
mance.
INPUT CAPACITOR
An input capacitor is required for stability. It is recommended
that a 1.0μF capacitor be connected between the LP5951
input pin and ground (this capacitance value may be in-
creased without limit).
This capacitor must be located a distance of not more than 1
cm from the input pin and returned to a clean analogue
ground.Any good quality ceramic, tantalum, or film capacitor
may be used at the input.
Important:
Tantalum capacitors can suffer catastrophic fail-
ures due to surge current when connected to a low-
impedance source of power (like a battery or a very large
capacitor). If a tantalum capacitor is used at the input, it must
be guaranteed by the manufacturer to have a surge current
rating sufficient for the application.
There are no requirements for the ESR (Equivalent Series
Resistance) on the input capacitor, but tolerance and tem-
perature coefficient must be considered when selecting the
capacitor to ensure the capacitance will remain
≥
0.7μF over
the entire operating temperature range.
OUTPUT CAPACITOR
The LP5951 is designed specifically to work with very small
ceramic output capacitors. The following ceramic capacitors
(dielectric types X7R, Z5U, or Y5V) are suitable as C
OUT
in
the LP5951 application circuit:
-V
OUT
<
2.8V: 1.0μF
-V
OUT
≥
2.8V: 1.5μF
C
can be increased up to 47μF, the ESR should be
between 3 m
to 500 m
.
This capacitor must be located a distance of not more than
1cm from the V
OUT
pin and returned to a clean analogue
ground.
It is also possible to use tantalum or film capacitors at the
device output, V
, but these are not as attractive for
reasons of size and cost (see the section Capacitor Charac-
teristics).
CAPACITOR CHARACTERISTICS
The LP5951 is designed to work with ceramic capacitors on
the output to take advantage of the benefits they offer. For
capacitance values in the range of 1μF to 4.7μF, ceramic
capacitors are the smallest, least expensive and have the
lowest ESR values, thus making them best for eliminating
high frequency noise. The ESR of a typical 1μF ceramic
capacitor is in the range of 3m
to 40m
, which easily
meets the ESR requirement for stability for the LP5951.
For both input and output capacitors, careful interpretation of
the capacitor specification is required to ensure correct de-
vice operation. The capacitor value can change greatly, de-
pending on the operating conditions and capacitor type.
In particular, the output capacitor selection should take ac-
count of all the capacitor parameters, to ensure that the
specification is met within the application. The capacitance
can vary with DC bias conditions as well as temperature and
frequency of operation. Capacitor values will also show
some decrease over time due to aging. The capacitor pa-
rameters are also dependant on the particular case size,
with smaller sizes giving poorer performance figures in gen-
eral. As an example,
Figure 1
shows a typical graph com-
paring different capacitor case sizes in a Capacitance vs. DC
Bias plot. As shown in the graph, increasing the DC Bias
condition can result in the capacitance value falling below
the minimum value given in the recommended capacitor
specifications table (0.7/1.1μF in this case). Note that the
graph shows the capacitance out of spec for the 0402 case
size capacitor at higher bias voltages. It is therefore recom-
mended that the capacitor manufacturers’ specifications for
the nominal value capacitor are consulted for all conditions,
as some capacitor sizes (e.g. 0402) may not be suitable in
the actual application.
L
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP5951MF-3.0 | 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 |
| LP5951MF-3.0/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(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 |
| LP5951MF-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 |
| LP5951MF-3.3/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 |
| LP5951MFX-1.3 | 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 |
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