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參數(shù)資料
| 型號： | LTC3780EUH |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | DIODE SCHOTTKY SINGLE 25V 200mW 0.4V-vf 200mA-IFM 10mA-IF 0.5uA-IR SOD-323 3K/REEL |
| 中文描述： | 3 A SWITCHING CONTROLLER, 440 kHz SWITCHING FREQ-MAX, PQCC32 |
| 封裝： | 5 X 5 MM, PLASTIC, MO-220WHHD, QFN-32 |
| 文件頁數(shù)： | 17/28頁 |
| 文件大?。?/td> | 421K |
| 代理商： | LTC3780EUH |
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17
LTC3780
3780f
APPLICATIU
Inductor Selection
The operating frequency and inductor selection are inter-
related in that higher operating frequencies allow the use
of smaller inductor and capacitor values. The inductor
value has a direct effect on ripple current. The inductor
current ripple
I
L
is typically set to 20% to 40% of the
maximum inductor current. For a given ripple the induc-
tance terms are as follows:
W
U
U
L
V
V
V
I
Ripple V
H
L
V
V
V
I
Ripple V
H
BOOST
IN MIN
(
OUT
%
IN MIN
(
OUT MAX
(
(
OUT
100
BUCK
OUT
IN MAX
(
%
OUT
OUT MAX
IN MAX
(
>
(
)
>
)
)
)
(
)
)
)
)
–
,
–
2
2
100
where:
f is operating frequency, Hz
% Ripple is allowable inductor current ripple, %
V
IN(MIN)
is minimum input voltage, V
V
IN(MAX)
is maximum input voltage, V
V
OUT
is output voltage, V
I
OUT(MAX)
is maximum output load current
For high efficiency, choose an inductor with low core loss,
such as ferrite and molypermalloy (from Magnetics, Inc.).
Also, the inductor should have low DC resistance to reduce
the I
2
R losses, and must be able to handle the peak
inductor current without saturating. To minimize radiated
noise, use a toroid, pot core or shielded bobbin inductor.
C
IN
and C
OUT
Selection
In Boost mode, input current is continuous. In Buck mode,
input current is discontinuous. In Buck mode, the selec-
tion of input capacitor C
IN
is driven by the need to filter the
input square wave current. Use a low ESR capacitor sized
to handle the maximum RMS current. For Buck operation,
the input RMS current is given by:
I
I
V
V
V
V
RMS
OUT MAX
(
OUT
IN
IN
OUT
≈
)
–1
This formula has a maximum at V
IN
= 2V
OUT
, where
I
RMS
= I
OUT(MAX)
/2. This simple worst-case condition is
commonly used for design because even significant
deviations do not offer much relief. Note that ripple
current ratings from capacitor manufacturers are often
based on only 2000 hours of life which makes it advisable
to derate the capacitor.
In Boost mode, the discontinuous current shifts from the
input to the output, so C
OUT
must be capable of reducing
the output voltage ripple. The effects of ESR (equivalent
series resistance) and the bulk capacitance must be con-
sidered when choosing the right capacitor for a given
output ripple voltage. The steady ripple due to charging
and discharging the bulk capacitance is given by:
Ripple Boost Cap
(
I
V
V
C
V
f
V
OUT MAX
(
OUT
IN MIN
(
OUT
OUT
,
)
–
)
)
=
(
)
Ripple Buck Cap
(
I
V
V
V
f
C
V
OUT MAX
(
IN MAX
(
OUT
OUT
IN MAX
(
,
)
–
)
)
)
=
(
)
where C
OUT
is the output filter capacitor.
The steady ripple due to the voltage drop across the ESR
is given by:
V
BOOST,ESR
= I
L(MAX,BOOST)
ESR
V
BUCK,ESR
= I
L(MAX,BUCK)
ESR
Multiple capacitors placed in parallel may be needed to
meet the ESR and RMS current handling requirements.
Dry tantalum, special polymer, aluminum electrolytic and
ceramic capacitors are all available in surface mount
packages. Ceramic capacitors have excellent low ESR
characteristics but can have a high voltage coefficient.
Capacitors are now available with low ESR and high ripple
current ratings such as OS-CON and POSCAP.
Power MOSFET Selection and
Efficiency Considerations
The LTC3780 requires four external N-channel power
MOSFETs, two for the top switches (Switch A and D,
shown in Figure 1) and two for the bottom switches
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC3780EUH#PBF | 功能描述:IC REG CTRLR BST 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:- 特色產(chǎn)品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 標準包裝:1 系列:PowerWise® PWM 型:電壓模式 輸出數(shù):1 頻率 - 最大:1MHz 占空比:81% 電源電壓:4.5 V ~ 18 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:-5°C ~ 125°C 封裝/外殼:32-WFQFN 裸露焊盤 包裝:Digi-Reel® 產(chǎn)品目錄頁面:1303 (CN2011-ZH PDF) 其它名稱:LM3754SQDKR |
| LTC3780EUH#PBF | 制造商:Linear Technology 功能描述:DC/DC Converter IC |
| LTC3780EUH#TR | 制造商:Linear Technology 功能描述:DC DC Cntrlr Dual-OUT Synchronous Boost/Buck Controller 4V to 36V Input 32-Pin QFN EP T/R |
| LTC3780EUH#TRPBF | 功能描述:IC REG CTRLR BST 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:- 標準包裝: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 |
| LTC3780EUHPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Step-Up/Down 36V QFN32 |
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