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參數(shù)資料
| 型號： | LP3986BL-2528 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | Dual Micropower 150 mA Ultra Low-Dropout CMOS Voltage Regulators in micro SMD Package |
| 中文描述： | DUAL OUTPUT, FIXED POSITIVE LDO REGULATOR, PBGA8 |
| 封裝： | 0.995 MM, MICRO, BUMP, SMD-8 |
| 文件頁數(shù)： | 10/13頁 |
| 文件大?。?/td> | 328K |
| 代理商： | LP3986BL-2528 |
Application Hints
EXTERNAL CAPACITORS
Like any low-dropout regulator, the LP3986 requires external
capacitors for regulator stability. The LP3986 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
LP3986 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 LP3986 is designed specifically to work with very small
ceramic output capacitors, any ceramic capacitor (tempera-
ture characteristics X7R, X5R, Z5U or Y5V) in 1 to 22 μF
range with 5m
to 500m
ESR range is suitable in the
LP3986 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.
NO-LOAD STABILITY
The LP3986 will remain stable and in regulation with no-load
(other than the internal voltage divider). This is specially
important in CMOS RAM keep-alive applications.
CAPACITOR CHARACTERISTICS
The LP3986 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
LP3986.
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 Y5 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
in the band gap reference circuit. Any significant loading on
this node will cause a change on the regulated output volt-
age. For this reason, DC leakage current through this pin
must be kept as low as possible for best output voltage
accuracy. The use of this 0.01μF bypass capacitor is strongly
recommended to prevent overshoot on the output during
start up.
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. Polypropolene and polycarbonate film capaci-
tors are available in small surface-mount packages and
typically have extremely low leakage current.
Unlike many other LDO’s, addition of a noise reduction
capacitor does not effect the transient response of the de-
vice.
ON/OFF INPUT OPERATION
The LP3986 is turned off by pulling the V
pin low, and
turned on by pulling it high. If this feature is not used, the V
pin should be tied to V
to keep the regulator output on at all
times. To assure proper operation, the signal source used to
drive the V
input must be able to swing above and below
the specified turn-on/off voltage thresholds listed in the Elec-
trical Characteristics section under V
IL
and V
IH
.
FAST ON-TIME
The LP3986 outputs are turned on after V
voltage reaches
its final value (1.23V nominal). To speed up this process, the
noise reduction capacitor at the bypass pin is charged with
an internal 70μAcurrent source. The current source is turned
off when the bandgap voltage reaches approximately 95% of
its final value. The turn on time is determined by the time
constant of the bypass capccitor. The smaller the capacitor
value, the shorter the turn on time, but less noise gets
reduced. As a result, turn on time and noise reduction need
to be taken into design consideration when choosing the
value of the bypass capacitor.
L
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| LP3986BL-2626 | 功能描述:IC REG LDO 2.6V .15A 8MICROSMD 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 標準包裝:2,500 系列:- 穩(wěn)壓器拓撲結(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（標準）:- 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 細型，TSOT-23-5 供應(yīng)商設(shè)備封裝:TSOT-23-5 包裝:帶卷 (TR) |
| LP3986BL-2818 | 功能描述:IC REG LDO 2.8V/1.8V 8-MICROSMD RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 標準包裝:3,000 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，可調(diào)式 輸出電壓:1.2 V ~ 5.5 V 輸入電壓:1.7 V ~ 5.5 V 電壓 - 壓降（標準）:0.075V @ 400mA 穩(wěn)壓器數(shù)量:1 電流 - 輸出:400mA（最小值） 電流 - 限制（最?。?400mA 工作溫度:-55°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應(yīng)商設(shè)備封裝:SOT-23-5 包裝:帶卷 (TR) 其它名稱:296-20789-2V62/06626-01XE |
| LP3986BL-2828 | 功能描述:IC REG LDO 2.8V .15A 8MICROSMD RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 產(chǎn)品變化通告:Heatsink Pkg Change 09/Oct/2007 標準包裝:50 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:24V 輸入電壓:最高 40 V 電壓 - 壓降（標準）:2V @ 1A 穩(wěn)壓器數(shù)量:1 電流 - 輸出:1A 電流 - 限制（最小）:- 工作溫度:0°C ~ 125°C 安裝類型:通孔 封裝/外殼:TO-220-3 供應(yīng)商設(shè)備封裝:TO-220-3 包裝:管件 |
| LP3986BL-285285 | 功能描述:IC REG LDO 2.85V .15A 8USMD RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 線性 系列:- 產(chǎn)品變化通告:Heatsink Pkg Change 09/Oct/2007 標準包裝:50 系列:- 穩(wěn)壓器拓撲結(jié)構(gòu):正，固定式 輸出電壓:24V 輸入電壓:最高 40 V 電壓 - 壓降（標準）:2V @ 1A 穩(wěn)壓器數(shù)量:1 電流 - 輸出:1A 電流 - 限制（最?。?- 工作溫度:0°C ~ 125°C 安裝類型:通孔 封裝/外殼:TO-220-3 供應(yīng)商設(shè)備封裝:TO-220-3 包裝:管件 |
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