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參數(shù)資料
| 型號(hào)： | LTC3772BETS8#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 650 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | 1 MM HEIGHT, LEAD FREE, PLASTIC, MO-193, TSOT-23, 8 PIN |
| 文件頁數(shù)： | 5/20頁 |
| 文件大小： | 318K |
| 代理商： | LTC3772BETS8#PBF |
13
LTC3772B
3772bfa
APPLICATIO S I FOR ATIO
WU
UU
For ceramic capacitors, use X7R or X5R types: do not use
Y5V. Manufacturers include AVX, Kemet, Murata, Taiyo
Yuden and TDK.
Setting Output Voltage
The LTC3772B output voltages are each set by an external
feedback resistor divider carefully placed across the out-
put as shown in Figure 3. The regulated output voltage is
determined by:
VV
R
OUT
B
A
=+
08
1
.
To improve the frequency response, a feed-forward capaci-
tor, CFF, may be used. Great care should be taken to route
the VFB line away from noise sources, such as the inductor
or the SW line.
Figure 3. Setting Output Voltage
VFB
VOUT
LTC3772B
RA
3772B F03
RB
CFF
1. The VIN current is the DC supply current, given in the
electrical characteristics, that excludes MOSFET driver
and control currents. VIN current results in a small loss
which increases with VIN.
2. MOSFET gate charge current results from switching the
gate capacitance of the power MOSFET. Each time a
MOSFET gate is switched from low to high to low again,
a packet of charge dQ moves from VIN to ground. The
resulting dQ/dt is a current out of VIN that is typically
much larger than the DC supply current. In continuous
mode, IGATECHG = (f)(dQ).
3. I2R losses are predicted from the DC resistances of the
MOSFET, inductor and current shunt. In continuous
mode the average output current flows through L but is
“chopped” between the P-channel MOSFET (in series
with RSENSE)andtheoutputdiode.TheMOSFETRDS(ON)
plus RSENSE multipliedbydutycyclecanbesummedwith
the resistances of L and RSENSE to obtain I2R losses.
4. The output diode is a major source of power loss at high
currents and gets worse at high input voltages. The diode
loss is calculated by multiplying the forward voltage
times the diode duty cycle multiplied by the load current.
For example, assuming a duty cycle of 50% with a Schot-
tky diode forward voltage drop of 0.4V, the loss increases
from 0.5% to 8% as the load current increases from 0.5A
to 2A.
5. Transition losses apply to the external MOSFET and
increase at higher operating frequencies and input volt-
ages. Transition losses can be estimated from:
Transition Loss = 2(VIN)2IO(MAX)CRSS(f)
Other losses including CIN and COUT ESR dissipative losses
and inductor core losses, generally account for less than
2% total additional loss.
Foldback Current Limiting
As described in the Output Diode Selection, the worst-case
dissipation occurs with a short-circuited output when the
diode conducts the current limit value almost continuously.
Efficiency Considerations
The efficiency of a switching regulator is equal to the out-
put power divided by the input power times 100%. It is often
useful to analyze individual losses to determine what is
limiting the efficiency and which change would produce the
most improvement. Efficiency can be expressed as:
Efficiency = 100% – (
η1 + η2 + η3 + ...)
where
η1, η2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, five main sources usually account for most of the
losses in LTC3772B circuits: 1) LTC3772B DC bias current,
2) MOSFET gate charge current, 3) I2R losses, 4) voltage
drop of the output diode and 5) external MOSFET transi-
tion losses.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3772EDDB#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin DFN EP |
| LTC3772EDDB#TRMPBF | 功能描述:IC REG CTRLR BUCK PWM CM 8-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3772EDDB#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 8-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 切換控制器 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- PWM 型:電流模式 輸出數(shù):1 頻率 - 最大:500kHz 占空比:96% 電源電壓:4 V ~ 36 V 降壓:無 升壓:是 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:24-WQFN 裸露焊盤 包裝:帶卷 (TR) |
| LTC3772ETS8 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 |
| LTC3772ETS8#PBF | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Step Down 2.75V to 9.8V Input 8-Pin TSOT-23 |
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