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參數(shù)資料
| 型號： | LP8345 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Low Dropout, Low IQ, 500mA CMOS Linear Regulator |
| 中文描述： | 低壓差，低IQ，500mA的CMOS線性穩(wěn)壓器 |
| 文件頁數(shù)： | 10/13頁 |
| 文件大?。?/td> | 283K |
| 代理商： | LP8345 |
Applications Section
GENERAL INFORMATION
The LP8345 is a low-dropout, low quiescent current linear
regulator. As shown in
Figure 1
it consists of a 1.25V refer-
ence, error amplifier, MOSFET driver, PMOS pass transistor
and for the fixed output versions, an internal feedback net-
work (R
1
/R
2
). In addition, the device is protected from over-
load by a thermal shutdown circuit and a foldback current
limit circuit.
The 1.25V reference is connected to the inverting input of
the error amplifier. Regulation of the output voltage is
achieved by means of negative feedback to the non-
inverting input of the error amplifier. Feedback resistors R
1
and R
are either internal or external to the device, depend-
ing on whether it is a fixed voltage version or the adjustable
version. The negative feedback and high open loop gain of
the error amplifier cause the two inputs of the error amp to be
virtually equal in voltage. If the output voltage changes due
to load changes, the error amplifier and MOSFET driver
provide the appropriate drive to the pass transistor to main-
tain the error amplifier’s inputs as virtually equal.
EXTERNAL CAPACITOR
An Input capacitor of 1μF or greater is required between the
LP8345 V
pin and ground. While 1μF will provide adequate
bypassing of the V
supply larger values of input capacitor
(i.e. 10μF) can provide improved bypassing of power supply
noise.
Stable operation can be achieved with an output capacitor of
1μF or greater, either ceramic X7R dielectric or aluminum/
tantalum electrolytic. While the minimum capacitor value is
1μF, the typical output capacitor values selected range from
1μF to 10μF. The larger values provide improved load-
transient response, power supply rejection and stability.
OUTPUT VOLTAGE SETTING (ADJ VERSION ONLY)
The output voltage is set according to the amount of nega-
tive feedback (Note that the pass transistor inverts the feed-
back signal). This feedback is determined by R
and R
with
the resulting output voltage represented by the following
equation:
Use the following equation to determine the values of R
1
and
R
2
for a desired V
OUT
(R
2
= 100
is recommended).
MINIMUM LOAD CURRENT
A minimum load of 100μA is required for regulation and
stability over the entire operating temperature range. If ac-
tual load current fall below 100μA it is recommended that a
resistor of value R
L
=V
O
/100μA be placed between V
O
and
ground.
20064803
FIGURE 1. LP8345 Functional Block Diagram
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LP8345A-1.8 E WAF | 制造商:Texas Instruments 功能描述: |
| LP8345A-2.5 E WAF | 制造商:Texas Instruments 功能描述: |
| LP8345A-3.3 E WAF | 制造商:Texas Instruments 功能描述: |
| LP8345A-5.0 E WAF | 制造商:Texas Instruments 功能描述: |
| LP8345CDT-1.8 | 制造商:Texas Instruments 功能描述:V REG LDO 0.5A 1.8V 8345 TO-252-3 |
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