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| 型号： | LT3800EFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR INV PWM CM 16-TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 220kHz |
| 占空比： | 95% |
| 电源电压： | 4 V ~ 60 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 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) |
LT3800
APPLICATIONS INFORMATION
Soft-Start Characteristic Showing Excessive Ripple Component
V OUT
V OUT(SS)
V(V C )
Desirable Soft-Start Characteristic
V OUT
V OUT(SS)
V(V C )
250μs/DIV
3800 AI07
250μs/DIV
3800 AI08
The soft-start cycle should be evaluated to verify that the
reduced R SS value allows operation without excessive
modulation of the V C pin before ?nalizing the design.
If the V C pin has an excessive ripple component during the
soft-start cycle, converter output ripple should be reduced
or R SS increased. Reduction in converter output ripple is
typically accomplished by increasing output capacitance
and/or reducing output capacitor ESR.
External Current Limit Foldback Circuit
An additional start-up voltage offset can occur during the
period before the LT3800 soft-start circuit becomes active.
Before the soft-start circuit throttles back the V C pin in
response to the rising output voltage, current as high as
the peak programmed current limit (I MAX ) can ?ow in the
inductor. Switching will stop once the soft-start circuit takes
hold and reduces the voltage on the V C pin, but the output
voltage will continue to increase as the stored energy in
the inductor is transferred to the output capacitor. With
I MAX ?owing in the inductor, the resulting leading-edge
rise on V OUT due to energy stored in the inductor follows
Inductor current typically doesn’t reach I MAX in the few
cycles that occur before soft-start becomes active, but can
with high input voltages or small inductors, so the above
relation is useful as a worst-case scenario.
This energy transfer increase in output voltage is typically
small, but for some low voltage applications with relatively
small output capacitors, it can become signi?cant. The volt-
age rise can be reduced by increasing output capacitance,
which puts additional limitations on C OUT for these low
voltage supplies. Another approach is to add an external
current limit foldback circuit which reduces the value of
I MAX during start-up.
An external current limit foldback circuit can be easily
incorporated into an LT3800 DC/DC converter application
by placing a 1N4148 diode and a 47k resistor from the
converter output (V OUT ) to the LT3800’s V C pin. This limits
the peak current to 0.25 ? I MAX when V OUT = 0V. A current
limit foldback circuit also has the added advantage of
providing a reduced output current in the DC/DC converter
during short-circuit fault conditions, so a foldback circuit
may be useful even if the soft-start function is disabled.
the relationship:
V OUT = I MAX ?
L
C OUT
1/2
If the soft-start circuit is disabled by shorting the C SS pin
to ground, the external current limit fold-back circuit must
be modi?ed by adding an additional diode and resistor.
The 2-diode, 2-resistor network shown also provides
0.25 ? I MAX when V OUT = 0V.
3800fc
12
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相关代理商/技术参数 |
参数描述 |
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| LT3800IFE | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4V to 60V 16-Pin TSSOP EP |
| LT3800IFE#PBF | 功能描述:IC REG CTRLR INV PWM CM 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 |
| LT3800IFE#PBF | 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN REGULATOR CTRL 16-TSSO |
| LT3800IFE#TR | 制造商:Linear Technology 功能描述:Conv DC-DC Single Step Down 4V to 60V 16-Pin TSSOP EP T/R |
| LT3800IFE#TRPBF | 功能描述:IC REG CTRLR INV PWM CM 16-TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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