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参数资料
| 型号： | LTC3783IFE#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 4.40 MM, PLASTIC, TSSOP-16 |
| 文件页数： | 7/24页 |
| 文件大小： | 250K |
| 代理商： | LTC3783IFE#TR |
LTC3783
15
3783fb
OPERATION
Boost Converter: Inductor Selection
Given an operating input voltage range, and having chosen
the operating frequency and ripple current in the inductor,
the inductor value can be determined using the following
equation:
L
V
If
D
where
I
IN MIN
L
MAX
L
OUT
=
Δ
Δ=
()
(
:
χ
M
MAX
D
)
–
1
Remember that most boost converters are not short-circuit
protected. Under a shorted output condition, the inductor
current is limited only by the input supply capability. For
applications requiring a step-up converter that is short-
circuit protected, please refer to the applications section
covering SEPIC converters.
The minimum required saturation current of the inductor
can be expressed as a function of the duty cycle and the
load current, as follows:
I
D
L SAT
OUT MAX
MAX
()
–
>+
1
21
χ
The saturation current rating for the inductor should be
checked at the minimum input voltage (which results in the
highest inductor current) and maximum output current.
Boost Converter: Operating in Discontinuous Mode
Discontinuous mode operation occurs when the load cur-
rent is low enough to allow the inductor current to run out
during the off-time of the switch, as shown in Figure 7.
Once the inductor current is near zero, the switch and diode
capacitances resonate with the inductance to form damped
ringing at 1MHz to 10MHz. If the off-time is long enough,
the drain voltage will settle to the input voltage.
Depending on the input voltage and the residual energy in
the inductor, this ringing can cause the drain of the power
MOSFET to go below ground where it is clamped by the body
diode. This ringing is not harmful to the IC and it has not
been shown to contribute signicantly to EMI. Any attempt
to damp it with a snubber will degrade the efciency.
Boost Converter: Power MOSFET Selection
The power MOSFET can serve two purposes in the LTC3783:
it represents the main switching element in the power path,
and its RDS(ON) can represent the current sensing element
for the control loop. Important parameters for the power
MOSFET include the drain-to-source breakdown voltage
BVDSS, the threshold voltage VGS(TH), the on-resistance
RDS(ON) versus gate-to-source voltage, the gate-to-source
and gate-to-drain charges QGS and QGD, respectively, the
maximum drain current ID(MAX) and the MOSFET’s thermal
resistances
θJC and θJA.
The gate drive voltage is set by the 7V INTVCC low drop
regulator. Consequently, 6V rated MOSFETs are required
in most high voltage LTC3783 applications. If low input
voltage operation is expected (e.g., supplying power
from a lithium-ion battery or a 3.3V logic supply), then
sublogic-level threshold MOSFETs should be used. Pay
close attention to the BVDSSspecicationsfortheMOSFETs
relative to the maximum actual switch voltage in the ap-
plication. Many logic-level devices are limited to 30V or
less, and the switch node can ring during the turn-off of
the MOSFET due to layout parasitics. Check the switching
waveforms of the MOSFET directly across the drain and
source terminals using the actual PC board layout for
excessive ringing.
OUTPUT
VOLTAGE
200mV/DIV
INDUCTOR
CURRENT
1A/DIV
1μs/DIV
3783 F07
MOSFET
DRAIN
VOLTAGE
20V/DIV
Figure 7. Discontinuous Mode Waveforms
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| LTC3785EUF#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
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| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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