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參數(shù)資料
| 型號： | LP2992ILDX-1.8 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | Micropower 250 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and LLP Packages Designed for Use with Very Low ESR Output Capacitors |
| 中文描述： | 1.8 V FIXED POSITIVE LDO REGULATOR, 0.85 V DROPOUT, PDSO6 |
| 封裝： | LLP-6 |
| 文件頁數(shù)： | 12/15頁 |
| 文件大小： | 598K |
| 代理商： | LP2992ILDX-1.8 |
Application Hints
EXTERNAL CAPACITORS
Like any low-dropout regulator, the LP2992 requires external
capacitors for regulator stability. These capacitors must be
correctly selected for good performance.
Input Capacitor
An input capacitor whose capacitance is
≥
1 μF is required
between the LP2992 input and ground (the amount of ca-
pacitance may be increased without limit).
This capacitor must be located a distance of not more than 1
cm 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-
ure
due
to
surge
current
low-impedance source of power (like a battery or 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 ESR on the input capacitor,
but tolerance and temperature coefficient must be consid-
ered when selecting the capacitor to ensure the capacitance
will be
≥
1 μF over the entire operating temperature range.
Output Capacitor:
The LP2992 is designed specifically to work with ceramic
output capacitors, utilizing circuitry which allows the regula-
tor to be stable across the entire range of output current with
an output capacitor whose ESR is as low as 5 m
. 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 the stable range.
Curves are provided which show the stable ESR range as a
function of load current (see ESR graph below).
when
connected
to
a
20029407
Important:
The output capacitor must maintain its ESR
within the stable region over the full operating temperature
range of the application to assure stability.
The LP2992 requires a minimum of 4.7 μF on the output
(output capacitor size can be increased without limit).
It is important to remember that capacitor tolerance and
variation with temperature must be taken into consideration
when selecting an output capacitor so that the minimum
required amount of output capacitance is provided over the
full operating temperature range. It should be noted that
ceramic capacitors can exhibit large changes in capacitance
with temperature (see next section,
Capacitor Characteris-
tics
).
The output capacitor must be located not more than 1 cm
from the output pin and returned to a clean analog ground.
Noise Bypass Capacitor:
Connecting a 10 nF capacitor to the Bypass pin significantly
reduces noise on the regulator output. It should be noted that
the capacitor is connected directly to a high-impedance cir-
cuit in the bandgap reference.
Because this circuit has only a few microamperes flowing in
it, any significant loading on this node will cause a change in
the regulated output voltage. For this reason, DC leakage
current through the noise bypass capacitor must never ex-
ceed 100 nA, and should be kept as low as possible for best
output voltage accuracy.
The types of capacitors best suited for the noise bypass
capacitor are ceramic and film. High-quality ceramic capaci-
tors with either NPO or COG dielectric typically have very
low leakage. 10 nF polypropolene and polycarbonate film
capacitors are available in small surface-mount packages
and typically have extremely low leakage current.
CAPACITOR CHARACTERISTICS
The LP2992 was designed to work with ceramic capacitors
on the output to take advantage of the benefits they offer: for
capacitance values in the 2.2 μF to 10 μF range, ceramics
are the least expensive and also have the lowest ESR
values
(which
makes
them
high-frequency noise). The ESR of a typical 4.7 μF ceramic
capacitor is in the range of 5 m
to 10 m
, which easily
meets the ESR limits required for stability by the LP2992.
One disadvantage of ceramic capacitors is that their capaci-
tance can vary with temperature. Most large value ceramic
capacitors (
≥
2.2 μF) are manufactured with the Z5U or Y5V
temperature characteristic, which results in the capacitance
dropping by more than 50% as the temperature goes from
25C to 85C.
This could cause problems if a 4.7 μF capacitor were used
on the output since it will drop down to approximately 2.3 μF
at high ambient temperatures (which could cause the
LP2992 to oscillate). If Z5U or Y5V capacitors are used on
the output, a minimum capacitance value of 10 μF must be
observed.
Abetter choice for temperature coefficient in ceramic capaci-
tors is X7R, which holds the capacitance within
±
15%. Un-
fortunately, the larger values of capacitance are not offered
by all manufacturers in the X7R dielectric.
Tantalum:
Tantalum capacitors are less desirable than ceramics for use
as output capacitors because they are more expensive when
comparing equivalent capacitance and voltage ratings in the
1 μF to 4.7 μF 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.
best
for
eliminating
L
www.national.com
12
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PDF描述 |
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| LP2992ILDX-2.5 | Micropower 250 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and LLP Packages Designed for Use with Very Low ESR Output Capacitors |
| LP2992ILDX-3.3 | Micropower 250 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and LLP Packages Designed for Use with Very Low ESR Output Capacitors |
| LP2992IM5-5.0 | Micropower 250 mA Low-Noise Ultra Low-Dropout Regulator in SOT-23 and LLP Packages Designed for Use with Very Low ESR Output Capacitors |
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| LP2992IM5X-1.8 | SMT-AL(V-CHIP) CAPACITANCE=10 VOLT=100 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP2992ILDX-2.5 | 功能描述:IC REG LDO 2.5V .25A 6-LLP 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) |
| LP2992ILDX-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 |
| LP2992ILDX-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 |
| LP2992ILDX-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 |
| LP2992ILDX-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 |
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