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參數(shù)資料
| 型號： | LP2951ACM |
| 廠商： | Semtech Corporation |
| 英文描述： | 150mA ADJUSTABLE VOLTAGE REGULATOR |
| 中文描述： | 150mA的可調(diào)電壓調(diào)節(jié)器 |
| 文件頁數(shù)： | 3/5頁 |
| 文件大?。?/td> | 112K |
| 代理商： | LP2951ACM |
LP2951A
1998 SEMTECH CORP.
150mA ADJUSTABLE
VOLTAGE REGULATOR
March 17, 1998
652 MITCHELL ROAD NEWBURY PARK CA 91320
3
PRINCIPLES OF OPERATION (LP2951 AND LP2951A)
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Setting the Output Voltage
The LP2951(A) can be set to deliver any output voltage
from 1.24V to 30V by using an external voltage divider.
In addition, an internal voltage divider is provided if a
5V output is desired. To use the internal voltage di-
vider, simply connect the sense pin to the output and
the tap pin to the feedback pin (see block diagram).
When using an external divider the sense and tap pins
are left open, and the divider is installed from the out-
put to ground, with its center connected to the feed-
back pin (see Adjustable Regulator figure below).
When using an external voltage divider, resistances
can be calculated from the following formula:
V
OUT =
An upper limit of values for R2 occurs at ~1.2M
if the
regulator is to be operated when completely unloaded,
as this allows the feedback divider to provide the 1A
minimum load recommended for the LP2951(A). If the
regulator always has a load of 1A or more connected
externally, higher resistor values can be used, but at-
tention must be paid to the -20nA (typical) bias current
required by the feedback pin. Using a 1.2M
resistor
for R2, this bias current will already cause a 2% shift in
output voltage between full load and no load. Larger
values of R2 exacerbate the problem. Using a 120K
resistor for R2 reduces the error caused by feedback
bias current to 0.2% while still only requiring 10A to
feed the divider string.
Output Filtering
An output filter capacitor is always necessary with the
LP2951(A) in order to assure output stability. The size
of this capacitor varies with output voltage (smaller at
lower output currents). For 5V operation 1F is suffi-
cient. For regulator operation at a minimum output volt-
age, (1.24V) and output currents of 100mA, the re-
quired filter increases to 3.3F. Any type of capacitor
may be used, although if aluminum electrolytics are
chosen, the equivalent series resistance (ESR) should
be held to 5
or less. For small load currents the ca-
pacitance can be reduced. 0.33F will be satisfactory
for output currents of 10mA or less, and 0.1F will
work if output current is below 1mA.
Theoretically, it is also possible for the regulator to be-
come unstable if very large capacitances (>10,000F)
are connected to the output, but this has not been ob-
served in practice. It is also important that the capaci-
tance be mounted close (1cm or less) to the output pin
of the regulator.
Adjustable Regulator
If the lead inductance between the input of the
LP2951(A) and its power source exceeds ~500nH
(approximately 10”/25cm of 0.031”/0.78mm trace) it
may also be necessary to add a filter capacitor be-
tween the input terminal and ground. A 1F tantalum
or aluminum capacitor is usually sufficient. Lower val-
ues can be used if load currents are small. Noise injec-
tion into the feedback terminal of the LP2951(A) from
nearby noise sources can also upset the output. Gen-
erally this can be cured by the addition of 100pF or so
from the feedback terminal to the output.
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相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LP2951A | 150mA Adjustable Voltage Regulators(低壓差，5V固定輸出或可調(diào)輸出(1.24-29V)，150mA穩(wěn)壓器) |
| LP2951CS-L-3.3 | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.45 V DROPOUT, PDSO8 |
| LP2951CS-L-5.0 | FIXED/ADJUSTABLE POSITIVE LDO REGULATOR, 0.45 V DROPOUT, PDSO8 |
| LP2985AITPX-2.8/NOPB | 2.8 V FIXED POSITIVE LDO REGULATOR, 0.575 V DROPOUT, PBGA5 |
| LP2985ITPX-2.8/NOPB | 2.8 V FIXED POSITIVE LDO REGULATOR, 0.575 V DROPOUT, PBGA5 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP2951ACM | 制造商:Texas Instruments 功能描述:V REG LDO ADJ +1.24/29V SMD 2951 |
| LP2951ACM | 制造商:Texas Instruments 功能描述:IC, ADJ LDO REG 1.24V TO 29V 0.1A 8-SOIC |
| LP2951ACM.TR | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| LP2951ACM/NOPB | 功能描述:低壓差穩(wěn)壓器 - LDO SERIES OF ADJUSTABLE MICROPOWER VLTG REGS 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 |
| LP2951ACM3.0 | 制造商:National Semiconductor 功能描述:LDO Regulator Pos 3V 0.1A 8-Pin SOIC N Rail |
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