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參數(shù)資料
| 型號(hào)： | LP3985IBLX-2.5 |
| 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-Noise Ultra Low-Dropout CMOS Voltage Regulator |
| 中文描述： | 2.5 V FIXED POSITIVE LDO REGULATOR, 0.1 V DROPOUT, PBGA5 |
| 封裝： | 0.995 MM HEIGHT, MICRO, SMD-5 |
| 文件頁(yè)數(shù)： | 13/17頁(yè) |
| 文件大?。?/td> | 570K |
| 代理商： | LP3985IBLX-2.5 |
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Typical Performance Characteristics
Unless otherwise specified, C
IN
= C
OUT
= 1 μF Ceramic,
C
BYPASS
= 0.01 μF, V
IN
= V
OUT
+ 0.2V, T
A
= 25C, Enable pin is tied to V
IN
. (Continued)
Output Impedance (V
IN
= 4.2V)
Output Impedance (V
IN
= V
OUT
+ 0.2V)
10136465
10136466
Application Hints
EXTERNAL CAPACITORS
Like any low-dropout regulator, the LP3985 requires external
capacitors for regulator stability. The LP3985 is specifically
designed for portable applications requiring minimum board
space and smallest components. These capacitors must be
correctly selected for good performance.
INPUT CAPACITOR
An input capacitance of
)
1μF is required between the
LP3985 input pin and ground (the amount of the capacitance
may be increased without limit).
This capacitor must be located a distance of not more than
1cm from the input pin and returned to a clean analog
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 on the input capaci-
tor, but tolerance and temperature coefficient must be con-
sidered when selecting the capacitor to ensure the capaci-
tance will be
)
1μF over the entire operating temperature
range.
OUTPUT CAPACITOR
The LP3985 is designed specifically to work with very small
ceramic output capacitors. A ceramic capacitor (temperature
characteristics X7R, X5R, Z5U, or Y5V) in 1 to 22 μF range
with 5m
to 500m
ESR range is suitable in the LP3985
application circuit.
It may also be possible to use tantalum or film capacitors at
the output, but these are not as attractive for reasons of size
and cost (see next section Capacitor Characteristics).
The output capacitor must meet the requirement for mini-
mum amount of capacitance and also have an ESR (Equiva-
lent Series Resistance) value which is within a stable range
(5 m
to 500 m
).
NO-LOAD STABILITY
The LP3985 will remain stable and in regulation with no
external load. This is specially important in CMOS RAM
keep-alive applications.
CAPACITOR CHARACTERISTICS
The LP3985 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 range,
ceramic capacitors are the smallest, least expensive and
have the lowest ESR values (which makes them best for
eliminating high frequency noise). The ESR of a typical 1μF
ceramic capacitor is in the range of 20 m
to 40 m
, which
easily meets the ESR requirement for stability by the
LP3985.
The ceramic capacitor’s capacitance can vary with tempera-
ture. The capacitor type X7R, which operates over a tem-
perature range of -55C to +125C, will only vary the capaci-
tance to within
±
15%. Most large value ceramic capacitors
(
)
2.2μF) are manufactured with Z5U or Y5V temperature
characteristics. Their capacitance can drop by more than
50% as the temperature goes from 25C to 85C. Therefore,
X7R is recommended over Z5U and Y5V in applications
where the ambient temperature will change significantly
above or below 25C.
Tantalum capacitors are less desirable than ceramic for use
as output capacitors because they are more expensive when
comparing equivalent capacitance and voltage ratings in the
1μF to 4.7μF range.
Another important consideration is that tantalum capacitors
have higher ESR values than equivalent size ceramics. This
means that while it may be possible to find a tantalum
capacitor with an ESR value within the stable range, it would
have to be larger in capacitance (which means bigger and
more costly ) than a ceramic capacitor with the same ESR
value. It should also be noted that the ESR of a typical
tantalum will increase about 2:1 as the temperature goes
from 25C down to 40C, so some guard band must be
allowed.
NOISE BYPASS CAPACITOR
Connecting a 0.01μF capacitor between the C
pin
and ground significantly reduces noise on the regulator out-
put. This cap is connected directly to a high impedance node
L
www.national.com
13
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP3985IBLX-285 | 功能描述:IC REG LDO 2.85V .15A 5USMD RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:2,500 系列:- 穩(wěn)壓器拓?fù)浣Y(jié)構(gòu):正，固定式 輸出電壓:3.1V 輸入電壓:最高 5.5V 電壓 - 壓降（標(biāo)準(zhǔn)）:- 穩(wěn)壓器數(shù)量:1 電流 - 輸出:300mA 電流 - 限制（最小）:420mA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細(xì)型，TSOT-23-5 供應(yīng)商設(shè)備封裝:TSOT-23-5 包裝:帶卷 (TR) |
| LP3985IBLX-285/NOPB | 制造商:Texas Instruments 功能描述:LDO Regulator Pos 2.85V 0.15A 5-Pin uSMD T/R |
| LP3985IBLX-3.0 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Micropower, 150mA Low-Noise Ultra Low-Dropout CMOS Voltage Regulator |
| LP3985IBLX-3.1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Micropower, 150mA Low-Noise Ultra Low-Dropout CMOS Voltage Regulator |
| LP3985IBLX-3.2 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Micropower, 150mA Low-Noise Ultra Low-Dropout CMOS Voltage Regulator |
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