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参数资料
| 型号： | LT3825EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 22/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR FLYBK ISO 16-TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 88% |
| 电源电压： | 11 V ~ 18 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
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LT3825
APPLICATIONS INFORMATION
? ? 1 + MIN ?
I PK(SEC) =
L LKG
+ V IN(MAX) + OUT(MAX)
BV DSS ≥ I PK
I RMS(PRI) =
? ? 1 + MIN ?
I PK(PRI) =
I RMS(SEC) =
OutputVoltageErrorSources
The LT3825’s feedback sensing introduces additional
sources of errors. The following is a summary list.
The internal bandgap voltage reference sets the reference
voltage for the feedback amplifier. The specifications detail
its variation.
The external feedback resistive divider ratio proportional
directly affects regulated voltage. Use 1% components.
Leakage inductance on the transformer secondary reduces
the effective secondary-to-feedback winding turns ratio
(N S /N F ) from its ideal value. This increases the output
voltage target by a similar percentage. Since secondary
leakage inductance is constant from part to part (with a
tolerance) adjust the feedback resistor ratio to compensate.
The transformer secondary current flows through the
impedances of the winding resistance, synchronous MOS-
FET R DS(ON) and output capacitor ESR. The DC equivalent
current for these errors is higher than the load current
because conduction occurs only during the converter’s
“off” time. So divide the load current by (1 – DC).
If the output load current is relatively constant, the feedback
resistive divider is used to compensate for these losses.
Otherwise, use the LT3825 load compensation circuitry
(see Load Compensation).
If multiple output windings are used, the flyback winding
will have a signal that represents an amalgamation of all
these windings impedances. Take care that you examine
worst-case loading conditions when tweaking the voltages.
Power MOSFET Selection
The power MOSFETs are selected primarily on the criteria of
on- resistance, R DS(ON) , input capacitance, drain-to-source
breakdown voltage (BV DSS ), maximum gate voltage (V GS )
and maximum drain current (I D(MAX) ).
For the primary-side power MOSFET, the peak current is:
P IN ? X ?
V IN(MIN) ? DC MAX ? 2 ?
For each secondary-side power MOSFET, the peak cur-
rent is:
I OUT ? X ?
1 – DC MAX ? 2 ?
Select a primary-side power MOSFET with a BV DSS greater
than:
V
C P N SP
where N SP reflects the turns ratio of that secondary-
to-primary winding. L LKG is the primary-side leakage
inductance and C P is the primary-side capacitance (mostly
from the C OSS of the primary-side power MOSFET). A
snubber may be added to reduce the leakage inductance
as discussed earlier.
For each secondary-side power MOSFET, the BV DSS should
be greater than:
BV DSS ≥ V OUT + V IN(MAX) ? N SP
Choose the primary-side MOSFET R DS(ON) at the nominal
gate drive voltage (7.5V). The secondary side MOSFET gate
drive voltage depends on the gate drive method.
Primary-side power MOSFET RMS current is given by:
P IN
V IN(MIN) DC MAX
For each secondary-side power MOSFET RMS current is
given by:
I OUT
1 – DC MAX
Calculate MOSFET power dissipation next. Because the
primary-side power MOSFET operates at high V DS , a transi-
tion power loss term is included for accuracy. C MILLER is
the most critical parameter in determining the transition
loss, but is not directly specified on the data sheets.
where X MIN is peak-to-peak current ratio as defined earlier.
3525fe
22
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相关代理商/技术参数 |
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|---|---|
| LT382B | 制造商:EDSYN 功能描述:TIP CONICAL 0.5X15.8MM |
| LT383 | 制造商:EDSYN 功能描述: |
| LT3837 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Low VIN, 8A DC/DC μModule Regulator |
| LT3837EFE | 制造商:Linear Technology 功能描述:Current Mode PWM Controller 16-Pin TSSOP EP |
| LT3837EFE#PBF | 功能描述:IC REG CTRLR FLYBK ISO 16-TSSOP 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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