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参数资料
| 型号： | LTC3547EDDB-1#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ .3A DL 8DFN |
| 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 ~ 5.5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 2.25MHz |
| 电流 - 输出： | 300mA |
| 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： | 8-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 8-DFN（3x2） |
LTC3547
APPLICATIO S I FOR ATIO
V OUT = 0 . 6 V ? 1 +
? R 1 ?
Setting the Output Voltage
The LTC3547 regulates the V FB1 and V FB2 pins to 0.6V
during regulation. Thus, the output voltage is set by a
resistive divider according to the following formula:
? R2 ?
(4)
Keeping the current small (< 5μA) in these resistors maxi-
mizes ef?ciency, but making it too small may allow stray
capacitance to cause noise problems or reduce the phase
margin of the error amp loop.
To improve the frequency response of the main control
loop, a feedback capacitor (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.
Fixed output versions of the LTC3547 (e.g. LTC3547-1)
include an internal resistive divider, eliminating the need
for external resistors. The resistor divider is chosen such
that the V FB input current is 3μA. For these versions the
V FB pin should be connected directly to V OUT . Table 2 lists
the ?xed output voltages available for the LTC35476-1.
Table 2. Fixed Output Voltage Versions
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 band-
width of the feedback loop, so the standard second-order
overshoot/DC ratio cannot be used to determine the phase
margin. In addition, feedback capacitors (C F1 and C F2 )
can be added to improve the high frequency response, as
shown in Figure 1. 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 ca-
pacitors. The discharged input capacitors are effectively
PART NUMBER
LTC3547
LTC3547-1
V OUT1
Adjustable
1.8V
V OUT2
Adjustable
1.2V
put in parallel 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
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
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 in-
corporates current limiting, short-circuit protection, and
soft-starting.
Hot Swap is a trademark of Linear Technology Corporation.
3547fa
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3548 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous,400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous, Fixed Output 2.25MHz Step-Down DC/DC Regulator |
| LTC3548-2 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous, Fixed/Adjustable Output, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548A | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
| LTC3548AEDD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Synchronous 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator |
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