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LTC3607EUD 参数 Datasheet PDF下载

LTC3607EUD图片预览
型号: LTC3607EUD
PDF下载: 下载PDF文件 查看货源
内容描述: [Dual 600mA 15V Monolithic Synchronous Step-Down DC/DC Regulator]
分类和应用:
文件页数/大小: 20 页 / 365 K
品牌: Linear Systems [ Linear Systems ]
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LTC3607  
applicaTions inForMaTion  
An important design consideration is that the R  
DS(ON)  
VOUT  
fO IL  
VOUT  
VIN(MAX)  
L=  
1–  
of the P-channel switch increases with decreasing input  
supply voltage (see Typical Performance Characteristics).  
Therefore, the user should calculate the power dissipation  
when the LTC3607 is used at 100% duty cycle with low  
input voltage (see Thermal Considerations in the Applica-  
tions Information section).  
The inductor value will also have an effect on Burst Mode  
operation. The transition from low current operation  
begins when the peak inductor current falls below a level  
set by the burst clamp. Lower inductor values result in  
higher ripple current which causes this transition to occur  
at lower load currents. This causes a dip in efficiency in  
the upper range of low current operation. In Burst Mode  
operation, lower inductance values will cause the burst  
frequency to increase.  
Low/High Supply Operation  
TheLTC3607incorporatesanundervoltagelockoutcircuit  
which shuts down the part when the input voltage drops  
below about 3.7V to prevent unstable operation.  
AgeneralLTC3607applicationcircuitisshowninFigure1.  
Externalcomponentselectionisdrivenbytheloadrequire-  
ment,andbeginswiththeselectionoftheinductorL.Once  
Inductor Core Selection  
Different core materials and shapes will change the size/  
currentandprice/currentrelationshipofaninductor.Toroid  
or shielded pot cores in ferrite or permalloy materials are  
small and don’t radiate much energy, but generally cost  
more than powdered iron core inductors with similar elec-  
tricalcharacteristics.Thechoiceofwhichstyleinductorto  
use often depends more on the price vs size requirements  
and any radiated field/EMI requirements than on what the  
LTC3607 requires to operate. Table 1 shows the websites  
of several surface mount inductor manufacturers.  
the inductor is chosen, C and C  
can be selected.  
IN  
OUT  
Inductor Selection  
The operating frequency directly effects both the inductor  
value, and the ripple current. The inductor ripple current  
ΔI decreases with higher frequency and/or inductance  
L
and increases with higher V :  
IN  
V
fO L  
V
VIN  
OUT   
∆IL = OUT 1–  
Table 1. Inductor Manufacturer  
Coilcraft  
http://www.coilcraft.com/powersel_lowl.html  
Accepting larger values of ΔI allows the use of low  
L
Cooper Bussmann http://www.cooperindustries.com/content/public/  
en/bussmann/electronics/products/coiltronics_  
inductances, but results in higher output voltage ripple,  
greater core losses, and lower output current capability.  
A reasonable starting point for setting ripple current is  
inductorandtransformermagnetics.html  
Würth Electronic  
Murata  
http://katalog.we-online.com/en/pbs/browse/  
Power-Magnetics/Speicherdrosseln  
ΔI = 0.4 • I  
, where I  
is the maximum rated  
L
O(MAX)  
O(MAX)  
http://www.murata.com/products/inductor/index.  
html  
output current. The largest ripple current ΔI occurs at  
L
the maximum input voltage. To guarantee that the ripple  
current stays below a specified maximum, the inductor  
valueshouldbechosenaccordingtothefollowingequation:  
TDK  
http://www.tdk.co.jp/tefe02/coil.htm  
Vishay  
http://www.vishay.com/inductors/power-  
inductors/  
Sumida  
http://www.sumida.com/en/products/  
power_main.php  
3607fb  
For more information www.linear.com/LTC3607  
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