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| 型号： | LTC3407EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1A DL 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.5MHz |
| 电流 - 输出： | 1A |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LTC3407
APPLICATIONS INFORMATION
?
V OUT = 0.6V ? 1 +
?
R2 ?
?
R1 ?
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
Keeping the current small (<5μA) in these resistors maxi-
mizes ef?ciency, but making them too small may allow
stray capacitance to cause noise problems and reduce the
phase margin of the error amp loop.
To improve the frequency response, a feed-forward capaci-
tor C F may also be used. Great care should be taken to
route the V FB line away from noise sources, such as the
inductor or the SW line.
Power-On Reset
The POR pin is an open-drain output which pulls low when
either regulator is out of regulation. When both output volt-
ages are within ±8.5% of regulation, a timer is started which
releases POR after 2 18 clock cycles (about 175ms). This
delay can be signi?cantly longer in Burst Mode operation
with low load currents, since the clock cycles only occur
during a burst and there could be milliseconds of time
between bursts. This can be bypassed by tying the POR
output to the MODE/SYNC input, to force pulse-skipping
mode during a reset. In addition, if the output voltage
faults during Burst Mode sleep, POR could have a slight
delay for an undervoltage output condition and may not
respond to an overvoltage output. This can be avoided by
using pulse-skipping mode instead. When either channel
is shut down, the POR output is pulled low, since one or
both of the channels are not in regulation.
Mode Selection & Frequency Synchronization
The MODE/SYNC pin is a multipurpose pin which provides
mode selection and frequency synchronization. Connect-
ing this pin to V IN enables Burst Mode operation, which
provides the best low current ef?ciency at the cost of a
higher output voltage ripple. When this pin is connected
to ground, pulse-skipping operation is selected which
provides the lowest output ripple, at the cost of low cur-
rent ef?ciency.
The LTC3407 can also be synchronized to another LTC3407
by the MODE/SYNC pin. During synchronization, the mode
is set to pulse-skipping and the top switch turn-on is syn-
chronized to the rising edge of the external clock.
several cycles to respond to a step in load current. When
a load step occurs, V OUT immediately shifts by an amount
equal to Δ I LOAD ? ESR, where ESR is the effective series
resistance of C OUT . Δ I LOAD also begins to charge or dis-
charge C OUT generating a feedback error signal used by the
regulator to return V OUT to its steady-state value. During
this recovery time, V OUT can be monitored for overshoot
or ringing that would indicate a stability problem.
The initial output voltage step may not be within the
bandwidth of the feedback loop, so the standard second-
order overshoot/DC ratio cannot be used to determine
phase margin. In addition, a feed-forward capacitor, C F ,
can be added to improve the high frequency response, as
shown in Figure 2. Capacitor C F provides phase lead by
creating a high frequency zero with R2 which improves
the phase margin.
The output voltage settling behavior is related to the stability
of the closed-loop system and will demonstrate the actual
overall supply performance. For a detailed explanation of
optimizing the compensation components, including a re-
view of control loop theory, refer to Application Note 76.
In some applications, a more severe transient can be caused
by switching in loads with large (>1μF) input capacitors.
The discharged input capacitors are effectively put in paral-
lel with C OUT , causing a rapid drop in V OUT . No regulator
can deliver enough current to prevent this problem, if the
switch connecting the load has low resistance and is driven
quickly. The solution is to limit the turn-on speed of the
load switch driver. A Hot Swap? controller is designed
speci?cally for this purpose and usually incorporates cur-
rent limiting, short-circuit protection, and soft-starting.
Ef?ciency Considerations
The percent ef?ciency of a switching regulator is equal to
the output power divided by the input power times 100%.
It is often useful to analyze individual losses to determine
what is limiting the ef?ciency and which change would
Hot Swap is a trademark of Linear Technology Corporation.
3407fa
10
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| LTC3407EMSE | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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| LTC3407EMSE#TR | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE-2 | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step Down 2.5V to 5.5V 10-Pin MSOP EP |
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