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| 型号： | LT3481EMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 10MSOP |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.27 V ~ 20 V |
| 输入电压： | 3.6 V ~ 34 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 300kHz ~ 2.8MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°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： | 管件 |
| 供应商设备封装： | 10-MSOP 裸露焊盘 |
| 产品目录页面： | 1331 (CN2011-ZH PDF) |
LT3481
APPLICATIONS INFORMATION
may not be fully charged. Because the boost capacitor is
charged with the energy stored in the inductor, the circuit
will rely on some minimum load current to get the boost
circuit running properly. This minimum load will depend
on input and output voltages, and on the arrangement of
the boost circuit. The minimum load generally goes to
zero once the circuit has started. Figure 6 shows a plot
of minimum load to start and to run as a function of input
voltage. In many cases the discharged output capacitor
will present a load to the switcher, which will allow it to
start. The plots show the worst-case situation where V IN
is ramping very slowly. For lower start-up voltage, the
boost diode can be tied to V IN ; however, this restricts the
input range to one-half of the absolute maximum rating
Soft-Start
The RUN/SS pin can be used to soft-start the LT3481,
reducing the maximum input current during start-up.
The RUN/SS pin is driven through an external RC ?lter to
create a voltage ramp at this pin. Figure 7 shows the start-
up and shutdown waveforms with the soft-start circuit.
By choosing a large RC time constant, the peak start-up
current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
of the resistor so that it can supply 20μA when the RUN/SS
pin reaches 2.3V.
of the BOOST pin.
At light loads, the inductor current becomes discontinu-
RUN
15k
I L
1A/DIV
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above V OUT . At higher load currents, the inductor
0.22μF
RUN/SS
GND
V RUN/SS
2V/DIV
V OUT
2V/DIV
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT3481, requiring a higher
2ms/DIV
3481 F07
input voltage to maintain regulation.
Figure 7. To Soft-Start the LT3481, Add a Resisitor
and Capacitor to the RUN/SS Pin
6.0
5.5
5.0
4.5
TO START
Synchronization
The internal oscillator of the LT3481 can be synchronized
to an external 275kHz to 475kHz clock by using a 5pF
4.0
3.5
3.0
2.5
2.0
TO RUN
V OUT = 3.3V
T A = 25°C
L = 4.7μ
f = 800 kHz
to 20pF capacitor to connect the clock signal to the RT
pin. The resistor tying the RT pin to ground should be
chosen such that the LT3481 oscillates 20% lower than
the intended synchronization frequency (see Setting the
0.001
0.01 0.1
LOAD CURRENT (A)
1
10
Switching Frequency section).
8.0
7.0
6.0
5.0
4.0
TO START
TO RUN
V OUT = 5.0V
The LT3481 should not be synchronized until its output
is near regulation as indicated by the PG ?ag. This can be
done with the system microcontroller/microprocessor or
with a discrete circuit by using the PG output. If a sync
signal is applied while the PG is low, the LT3481 may
exhibit erratic operation. See Typical Applications.
3.0
2.0
0.001
0.01
0.1
T A = 25°C
L = 4.7μ
f = 800 kHz
1
10
When applying a sync signal, positive clock transitions
reset LT3481’s internal clock and negative transitions
LOAD CURRENT (A)
3481 F06
initiate a switch cycle. The amplitude of the sync signal
Figure 6. The Minimum Input Voltage Depends on
must be at least 2V. The sync signal duty cycle can range
Output Voltage, Load Current and Boost Circuit
3481fc
15
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3481EMSE-TR | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 2.8MHz Step-Down Switching Regulator with 50μA Quiescent Current |
| LT3481EMSE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 2.8MHz Step-Down Switching Regulator with 50μA Quiescent Current |
| LT3481HDD | 制造商:Linear Technology 功能描述:SW REG 36V 2A 2.8MHZ SD 10DFN |
| LT3481HDD#PBF | 功能描述:IC REG BUCK ADJ 2A 10DFN 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 |
| LT3481HDD#PBF | 制造商:Linear Technology 功能描述:SW REG 36V 2A 2.8MHZ SD 10DFN |
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