參數(shù)資料
型號(hào)： LTC3731H
廠商： Linear Technology Corporation
英文描述： 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller
中文描述： 3相，600kHz的，同步降壓開(kāi)關(guān)穩(wěn)壓器控制器
文件頁(yè)數(shù)： 14/32頁(yè)
文件大小： 323K
代理商： LTC3731H
14
LTC3731H
3731hf
in applications that have an output voltage that is less than
1/3 of the input voltage. In applications where V
IN
>> V
OUT
,
the top MOSFETs’ “on” resistance is normally less impor-
tant for overall efficiency than its input capacitance at
operating frequencies above 300kHz. MOSFET manufac-
turers have designed special purpose devices that provide
reasonably low “on” resistance with significantly reduced
input capacitance for the main switch application in switch-
ing regulators.
The peak-to-peak MOSFET gate drive levels are set by the
voltage, V
CC
, requiring the use of logic-level threshold
MOSFETs in most applications. Pay close attention to the
BV
DSS
specification for the MOSFETs as well; many of the
logic-level MOSFETs are limited to 30V or less.
Selection criteria for the power MOSFETs include the “on”
resistance R
DS(ON)
, input capacitance, input voltage and
maximum output current.
MOSFET input capacitance is a combination of several
components but can be taken from the typical “gate
charge” curve included on most data sheets (Figure 5).
The curve is generated by forcing a constant input current
into the gate of a common source, current source loaded
stage and then plotting the gate voltage versus time. The
initial slope is the effect of the gate-to-source and the gate-
to-drain capacitance. The flat portion of the curve is the
result of the Miller multiplication effect of the drain-to-gate
capacitance as the drain drops the voltage across the
current source load. The upper sloping line is due to the
drain-to-gate accumulation capacitance and the gate-to-
source capacitance. The Miller charge (the increase in
coulombs on the horizontal axis from a to b while the curve
is flat) is specified for a given V
DS
drain voltage, but can be
adjusted for different V
DS
voltages by multiplying by the
ratio of the application V
DS
to the curve specified V
DS
values. A way to estimate the C
MILLER
term is to take the
change in gate charge from points a and b on a manufac-
turers data sheet and divide by the stated V
DS
voltage
specified. C
MILLER
is the most important selection criteria
for determining the transition loss term in the top MOSFET
but is not directly specified on MOSFET data sheets. C
RSS
and C
OS
are specified sometimes but definitions of these
parameters are not included.
When the controller is operating in continuous mode the
duty cycles for the top and bottom MOSFETs are given by:
MainSwitchDutyCycle
V
V
SynchronousSwitchDutyCycle
V
V
V
OUT
IN
IN
OUT
IN
=
=
–
MOSFETs at maximum output current are given by:
P
V
V
I
N
R
V
I
N
1
R
(
C
V
V
V
f
P
V
V
V
I
N
R
MAIN
OUT
IN
2
MAX
DS ON
(
IN
MAX
2
DR
MILLER
CC
T( )
T( )
2
SYNC
IN
OUT
IN
MAX
DS ON
(
=
+
(
)
+
)(
)
+
( )
=
+
(
)
2
1
1
1
δ
δ
)
)
–
–
where N is the number of output stages,
δ
is the tempera-
ture dependency of R
DS(ON)
, R
DR
is the effective top driver
resistance (approximately 2
at V
GS
= V
MILLER
), V
IN
is the
drain potential andthe change in drain potential in the
particular application. V
TH(IL)
is the data sheet specified
typical gate threshold voltage specified in the power
MOSFET data sheet at the specified drain current. C
MILLER
is the calculated capacitance using the gate charge curve
from the MOSFET data sheet and the technique described
above.
APPLICATIOU
W
U
U
+
–
V
DS
V
IN
3731H F05
V
GS
–
MILLER EFFECT
Q
IN
a
b
C
MILLER
= (Q
B
– Q
A
)/V
DS
V
GS
V
+
Figure 5. Gate Charge Characteristic
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LTC3731HG 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
LTC3731HG#PBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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LTC3731HG#TRPBF 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:PolyPhase® 標(biāo)準(zhǔn)包裝:4,500 系列:PowerWise® PWM 型:控制器 輸出數(shù):1 頻率 - 最大:1MHz 占空比:95% 電源電壓:2.8 V ~ 5.5 V 降壓:是 升壓:無(wú) 回掃:無(wú) 反相:無(wú) 倍增器:無(wú) 除法器:無(wú) Cuk:無(wú) 隔離:無(wú) 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤(pán) 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX
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