參數(shù)資料
型號(hào)： LTC3738
廠商： Linear Technology Corporation
英文描述： 16-Bit Buffer/Driver With 3-State Outputs 48-TSSOP -40 to 85
中文描述： 三相降壓控制器與Active定位電壓英特爾VRM9/VRM10
文件頁(yè)數(shù)： 17/32頁(yè)
文件大小： 316K
代理商： LTC3738
17
LTC3738
3738f
The Schottky diodes shown in the Typical Application on
the first page of this data sheet conduct during the dead
time between the conduction of the two large power
MOSFETs. This prevents the body diode of the bottom
MOSFET from turning on, storing charge during the dead
time and requiring a reverse recovery period which could
cost as much as several percent in efficiency. A 2A to 8A
Schottky is generally a good compromise for both regions
of operation due to the relatively small average current.
Larger diodes result in additional transition losses due to
their larger junction capacitance.
C
IN
and C
OUT
Selection
Input capacitance ESR requirements and efficiency losses
are reduced substantially in a multiphase architecture
because the peak current drawn from the input capacitor
is effectively divided by the number of phases used and
power loss is proportional to the RMS current squared. A
3-stage, single output voltage implementation can reduce
input path power loss by 90%.
In continuous mode, the source current of each top
N-channel MOSFET is a square wave of duty cycle V
OUT
/V
IN
.
A low ESR input capacitor sized for the maximum RMS
current must be used. The details of a close form equation
can be found in Application Note 77. Figure 5 shows the
input capacitor ripple current for different phase configu-
rations with the output voltage fixed and input voltage
varied. The input ripple current is normalized against the
DC output current. The graph can be used in place of
tedious calculations. The minimum input ripple current
can be achieved when the product of phase number and
output voltage, N(V
OUT
), is approximately equal to the
input voltage V
IN
or:
V
V
k
N
where k
N
OUT
IN
=
=
, ,..., –
1
So the phase number can be chosen to minimize the input
capacitor size for the given input and output voltages.
In the graph of Figure 5, the local maximum input RMS
capacitor currents are reached when:
V
V
k
N
where k
N
OUT
IN
=
=
2
1
, ,...,
–
These worst-case conditions are commonly used for de-
sign because even significant deviations do not offer much
relief. Note that capacitor manufacturer’s ripple current
ratings are often based on only 2000 hours of life. This
makes it advisable to further derate the capacitor or to
choose a capacitor rated at a higher temperature than re-
quired. Several capacitors may also be paralleled to meet
size or height requirements in the design. Always consult
the capacitor manufacturer if there is any question.
The Figure 5 graph shows that the peak RMS input current
is reduced linearly, inversely proportional to the number N
of stages used. It is important to note that the efficiency
loss is proportional to the input RMS current squared and
therefore a 3-stage implementation results in 90% less
power loss when compared to a single phase design. Bat-
tery/input protection fuse resistance (if used), PC board
trace and connector resistance losses are also reduced by
the reduction of the input ripple current in a PolyPhase
system. The required amount of input capacitance is
further reduced by the factor, N, due to the effective in-
crease in the frequency of the current pulses.
Ceramic capacitors are becoming very popular for small
designs but several cautions should be observed. “X7R”,
“X5R” and “Y5V” are examples of a few of the ceramic
materials used as the dielectric layer, and these different
dielectrics have very different effect on the capacitance
value due to the voltage and temperature conditions
APPLICATIOU
W
U
U
DUTY FACTOR (V
OUT
/V
IN
)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.6
0.5
0.4
0.3
0.2
0.1
0
3738 F05
R
D
6-PHASE
4-PHASE
3-PHASE
2-PHASE
1-PHASE
Figure 5. Normalized Input RMS Ripple Current
vs Duty Factor for One to Six Output Stages
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參數(shù)描述
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LTC3738CUHF#PBF 功能描述:IC CTRLR SW REG 3PH STPDWN 38QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
LTC3738CUHF#TR 功能描述:IC CTRLR SW REG 3PH STPDWN 38QFN RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
LTC3738CUHF#TRPBF 功能描述:IC CTRLR SW REG 3PH STPDWN 38QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - 專用型 系列:- 標(biāo)準(zhǔn)包裝:43 系列:- 應(yīng)用:控制器，Intel VR11 輸入電壓:5 V ~ 12 V 輸出數(shù):1 輸出電壓:0.5 V ~ 1.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:48-VFQFN 裸露焊盤 供應(yīng)商設(shè)備封裝:48-QFN（7x7） 包裝:管件
LTC-3743KG 制造商:Lite-On Semiconductor Corporation 功能描述:
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