參數(shù)資料
型號(hào)： LT3509IMSE#PBF
廠商： LINEAR TECHNOLOGY CORP
元件分類： 穩(wěn)壓器
英文描述： 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO16
封裝： LEAD FREE, PLASTIC, MSOP-16
文件頁(yè)數(shù)： 2/24頁(yè)
文件大?。?/td> 271K
代理商： LT3509IMSE#PBF
LT3509
10
3509fc
APPLICATIONS INFORMATION
External Synchronization
The external synchronization provides a trigger to the
internal oscillator. As such, it can only raise the frequency
above the free-run value. To allow for device and
component tolerances, the free run frequency should be
set to at least 12% lower than the lowest supplied external
synchronization reference. The oscillator and hence the
switching frequency can then pushed up from 12% above
the free-run frequency, set by the selected RT. For example,
if the minimum external clock is 300kHz, the RT should
be chosen for 264kHz.
The SYNC input has a threshold of 1.0V nominal so it is
compatible with most logic levels. The duty cycle is not
critical provided the high or low pulse width is at least
80ns.
Design Procedure
Before starting detailed design a number of key design
parameters should be established as these may affect
design decisions and component choices along the way.
One of the main things to determine apart from the desired
output voltages is the input voltage range. Both the normal
operating range and the extreme conditions of surges
and/or dips or brown-outs need to be known. Then the
operating frequency should be considered and if there
are particular requirements to avoid interference. If there
are very specic frequencies that need to be avoided then
external synchronization may be needed. This could also be
desirable if multiple switchers are used as low frequency
beating between similar devices can be undesirable. For
efcient operation this converter requires a boost supply so
that the base of the output transistor can be pumped above
the input voltage during the switch on time. Depending
on the input and output voltages the boost supply can be
provided by the input voltage, one of the regulated outputs
or an independent supply such as an LDO.
Input Voltage Range
Firstly, the LT3509 imposes some hard limits due to the
undervoltage lock-out and the overvoltage protection. A
given application will also have a reduced, normal operating
range over which maximum efciency and lowest ripple
are obtained. This usually requires that the device is
operating at a xed frequency without skipping pulses.
There may also be zones above and below the normal
range where regulation is maintained but efciency and
ripple may be compromised. At the low end, insufcient
input voltage will cause loss of regulation and increased
ripple—this is the dropout range. At the high end if the
duty cycle becomes too low this will cause pulse skipping
and excessive ripple. This is the pulse-skip region. Both
situations also lead to higher noise at frequencies other than
the chosen switching frequency. Occasional excursions
into pulse-skip mode, during surges for example, may be
tolerable. Pulse skipping will also occur at light loads even
within the normal operating range but ripple is usually not
degraded because at light load the output capacitor can
hold the voltage steady between pulses.
For input voltages greater than 30V, there are restrictions
on the inductor value. See the Inductor Selection section
for details.
To ensure the regulator is operating in continuous mode
it is necessary to calculate the duty cycle for the required
output voltage over the full input voltage range. This must
then be compared with minimum and maximum practical
duty cycles.
相關(guān)PDF資料
PDF描述
LT3509IMSE#TRPBF 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO16
LT3509EMSE#TRPBF 1.2 A DUAL SWITCHING CONTROLLER, 2500 kHz SWITCHING FREQ-MAX, PDSO16
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT3509IMSE-TRPBF 制造商:LINER 制造商全稱:Linear Technology 功能描述:Dual 36V, 700mA Step-Down Regulator
LT350A 功能描述:氣體放電管 - GDT /氣體等離子體避雷器 350V RoHS:否 制造商:Bourns 峰值脈沖電流: 直流擊穿電壓（標(biāo)稱）:4500 V 電極數(shù)量:2 系列:SA2 端接類型:Axial 故障安全保護(hù) Y/N: 封裝:Reel
LT350A-B 功能描述:氣體放電管 - GDT /氣體等離子體避雷器 350V RoHS:否 制造商:Bourns 峰值脈沖電流: 直流擊穿電壓（標(biāo)稱）:4500 V 電極數(shù)量:2 系列:SA2 端接類型:Axial 故障安全保護(hù) Y/N: 封裝:Reel
LT350AK 制造商:Linear Technology 功能描述:Standard Regulator Pos 3A 3-Pin(2+Tab) TO-3
LT350AT 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Positive Adjustable Voltage Regulator
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