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參數(shù)資料
| 型號： | LTC3731HG |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller |
| 中文描述： | 5 A SWITCHING CONTROLLER, 750 kHz SWITCHING FREQ-MAX, PDSO36 |
| 封裝： | 5.3 MM, PLASTIC, SSOP-36 |
| 文件頁數(shù)： | 15/32頁 |
| 文件大?。?/td> | 323K |
| 代理商： | LTC3731HG |
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15
LTC3731H
3731hf
Both MOSFETs have I
2
R losses while the topside N-channel
equation includes an additional term for transition losses,
which peak at the highest input voltage. For V
IN
< 12V, the
high current efficiency generally improves with larger
MOSFETs, while for V
IN
> 12V, the transition losses
rapidly increase to the point that the use of a higher
R
DS(ON)
device with lower C
MILLER
actually provides higher
efficiency. The synchronous MOSFET losses are greatest
at high input voltage when the top switch duty factor is low
or during a short circuit when the synchronous switch is
on close to 100% of the period.
The term (1 +
δ
) is generally given for a MOSFET in the
form of a normalized R
DS(ON)
vs temperature curve, but
δ
= 0.005/
°
C can be used as an approximation for low
voltage MOSFETs.
The Schottky diodes, D1 to D3 shown in Figure 1 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 transi-
tion loss due to their larger junction capacitance.
C
IN
and C
OUT
Selection
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 6 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 4, 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 6 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
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
3731H F06
R
D
6-PHASE
12-PHASE
4-PHASE
3-PHASE
2-PHASE
1-PHASE
Figure 6. Normalized Input RMS Ripple Current
vs Duty Factor for One to Six Output Stages
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3731HG#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731HG#TR | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:否 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731HG#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 36-SSOP RoHS:是 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731HUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
| LTC3731HUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 類別: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 回掃:無 反相:無 倍增器:無 除法器:無 Cuk:無 隔離:無 工作溫度:-40°C ~ 125°C 封裝/外殼:6-WDFN 裸露焊盤 包裝:帶卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名稱:LM1771SSDX |
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