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| 型号： | LT3958EUHE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/28页 |
| 文件大小： | 0K |
| 描述： | IC REG MULTI CONFIG ADJ 36VQFN |
| 特色产品： | LT?3957/LT?3958 Converters |
| 标准包装： | 61 |
| 类型： | 升压（升压），反相，回扫，Sepic |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.6 V ~ 80 V |
| 输入电压： | 5 V ~ 80 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 100kHz ~ 1MHz |
| 电流 - 输出： | 3.3A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 36-WFQFN 裸露焊盘 |
| 包装： | 管件 |
| 供应商设备封装： | 36-QFN-EP（6x5） |
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LT3958
APPLICATIONS INFORMATION
Inverting Converter: Switch Duty Cycle and Frequency
For an inverting converter operating in CCM, the duty cycle
of the main switch can be calculated based on the negative
output voltage (V OUT ) and the input voltage (V IN ).
The maximum duty cycle (D MAX ) occurs when the converter
has the minimum input voltage:
Inverting Converter: Selecting the DC Coupling Capacitor
The DC voltage rating of the DC coupling capacitor
(C DC , as shown in Figure 10) should be larger than the
maximum input voltage minus the output voltage (nega-
tive voltage):
V CDC > V IN(MAX) – V OUT
D MAX =
V OUT ? V D
V OUT ? V D ? V IN(MIN)
C DC has nearly a rectangular current waveform. During
the switch off-time, the current through C DC is I IN , while
approximately –I O ?ows during the on-time. The RMS
Inverting Converter: Output Diode and Input Capacitor
Selections
rating of the coupling capacitor is determined by the fol-
lowing equation:
The selections of the inductor, output diode and input
capacitor of an inverting converter are similar to those
I RMS(CDC) > I O(MAX) ?
D MAX
1 ? D MAX
Δ V OUT(P – P) = Δ I L2 ? ? ESR COUT +
oftheSEPICconverter.Pleaserefertothecorresponding
SEPIC converter sections.
Inverting Converter: Output Capacitor Selection
The inverting converter requires much smaller output
capacitors than those of the boost, ?yback and SEPIC
converters for similar output ripples. This is due to the fact
that, in the inverting converter, the inductor L2 is in series
with the output, and the ripple current ?owing through the
output capacitors are continuous. The output ripple voltage
is produced by the ripple current of L2 ?owing through the
ESR and bulk capacitance of the output capacitor:
? 1 ?
?
? 8 ? ? ? C OUT ?
After specifying the maximum output ripple, the user can
select the output capacitors according to the preceding
equation.
The ESR can be minimized by using high quality X5R or
X7R dielectric ceramic capacitors. In many applications,
ceramic capacitors are suf?cient to limit the output volt-
age ripple.
The RMS ripple current rating of the output capacitor
needs to be greater than:
I RMS(COUT) > 0.3 ? Δ I L2
A low ESR and ESL, X5R or X7R ceramic capacitor works
well for C DC .
Board Layout
The high power and high speed operation of the LT3958
demands careful attention to board layout and component
placement. Careful attention must be paid to the internal
power dissipation of the LT3958 at high input voltages,
high switching frequencies, and high internal power switch
currents to ensure that a junction temperature of 125°C is
not exceeded. This is especially important when operating
at high ambient temperatures. Exposed pads on the bot-
tom of the package are SGND and SW terminals of the IC,
and must be soldered to a SGND ground plane and a SW
plane respectively. It is recommended that multiple vias
in the printed circuit board be used to conduct heat away
from the IC and into the copper planes with as much as
area as possible.
To prevent radiation and high frequency resonance
problems, proper layout of the components connected
to the IC is essential, especially the power paths with
higher di/dt. The following high di/dt loops of different
topologies should be kept as tight as possible to reduce
inductive ringing:
? In boost con?guration, the high di/dt loop contains
the output capacitor, the internal power MOSFET and
the Schottky diode.
3958f
21
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3958EUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHE#PBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3958IUHE#TRPBF | 功能描述:IC REG MULTI CONFIG ADJ 36VQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT3958IUHEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
| LT3958IUHETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Input Voltage, Boost, Flyback, SEPIC and Inverting Converter |
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