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| 型号： | LT3579EFE-1#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PDSO20 |
| 封装： | 4.40 MM, LEAD FREE, PLASTIC, TSSOP-20 |
| 文件页数： | 13/40页 |
| 文件大小： | 503K |
| 代理商： | LT3579EFE-1#PBF |
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LT3579/LT3579-1
20
35791f
applicaTions inForMaTion
SWITCHING FREQUENCY
There are several considerations in selecting the operating
frequency of the converter. The first is staying clear of
sensitive frequency bands, which cannot tolerate any
spectral noise. For example, in products incorporating RF
communications, the 455kHz IF frequency is sensitive to
any noise, therefore switching above 600kHz is desired.
Some communications have sensitivity to 1.1MHz and in
that case a 1.5MHz switching converter frequency may be
employed. The second consideration is the physical size
of the converter. As the operating frequency goes up, the
inductor and filter capacitors go down in value and size.
The tradeoff is efficiency, since the switching losses due to
NPN base charge (see Thermal Considerations), Schottky
diode charge, and other capacitive loss terms increase
proportionally with frequency.
Oscillator Timing Resistor (RT)
The operating frequency of the LT3579 can be set by the
internalfree-runningoscillator.WhentheSYNCpinisdriven
low (< 0.4V), the frequency of operation is set by a resistor
from the RT pin to ground. An internally trimmed timing
capacitor resides inside the IC. The oscillator frequency
is calculated using the following formula:
fOSC =
87.6
RT + 1
where fOSC is in MHz and RT is in kΩ. Conversely, RT (in
kΩ) can be calculated from the desired frequency (in
MHz) using:
RT =
87.6
fOSC
– 1
Thepublished(http://www.linear.com/designtools/packag-
ing/Linear_Technology_Thermal_Resistance_Table.pdf)
θJA value is 38°C/W for the TSSOP Exposed Pad package
and 34°C/W for the 4mm
×5mmQFNpackage.Inpractice,
lower
θJAvaluesarerealizableifboardlayoutisperformed
with appropriate grounding (accounting for heat sinking
properties of the board) and other considerations listed in
the Layout Guidelines section. For instance, a
θJA value of
~22°C/W was consistently achieved for both TSSOP and
QFN packages of the LT3579 (at VIN = 5V, VOUT = 12V,
IOUT=1.7A,fOSC=1MHz)whenboardlayoutwasoptimized
as per the suggestions in the Layout Guidelines section.
Junction Temperature Measurement
ThedutycycleoftheCLKOUTsignalontheLT3579islinearly
proportional to die junction temperature, TJ (the CLKOUT
duty cycle on the LT3579-1 is fixed at ~50%). To get an
accurate reading, measure the duty cycle of the CLKOUT
signal and use the following equation to approximate the
junction temperature:
TJ =
DCCLKOUT – 35%
0.3%
where DCCLKOUT is the CLKOUT duty cycle in % and TJ is
the die junction temperature in °C. Although the absolute
die temperature can deviate from the above equation by
±15°C, the relationship between change in CLKOUT duty
cycle and change in die temperature is well defined. A
3% increase in CLKOUT duty cycle corresponds to ~10°C
increase in die temperature:
Note that the CLKOUT pin is only meant to drive capacitive
loads up to 50pF.
Thermal Lockout
A fault condition occurs when the die temperature exceeds
~165°C(seeOperation–FAULTSection),andthepartgoes
into thermal lockout. The fault condition ceases when the
die temperature drops by ~5°C (nominal).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3579EFE-1-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:6A Boost/Inverting DC/DC Converter with Fault Protection |
| LT3579EFE-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:6A Boost/Inverting DC/DC Converter with Fault Protection |
| LT3579EFE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:6A Boost/Inverting DC/DC Converter with Fault Protection |
| LT3579EUFD#PBF | 功能描述:IC REG MULTI CONFIG SYNC 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3579EUFD#TRPBF | 功能描述:IC REG MULTI CONFIG SYNC 20QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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