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| 型号： | LT3685IMSE#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： | 0.79 V ~ 20 V |
| 输入电压： | 3.6 V ~ 36 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 200kHz ~ 2.4MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 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： | 管件 |
| 供应商设备封装： | 10-MSOP |
| 产品目录页面： | 1332 (CN2011-ZH PDF) |
LT3685
APPLICATIONS INFORMATION
6.0
5.5
TO START
5.0
4.5
4.0
(WORST CASE)
RUN
15k
RUN/SS
I L
1A/DIV
V RUN/SS
3.5
3.0
2.5
2.0
1
TO RUN
V OUT = 3.3V
T A = 25°C
L = 8.2μH
f = 700kHz
10
100 1000
10000
0.22μF
GND
2ms/DIV
3685 F06
2V/DIV
V OUT
2V/DIV
8.0
LOAD CURRENT (A)
Figure 6. To Soft-Start the LT3685, Add a Resisitor
and Capacitor to the RUN/SS Pin
7.0
6.0
5.0
4.0
3.0
TO START
(WORST CASE)
TO RUN
V OUT = 5V
T A = 25°C
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 2.5V.
Synchronization
2.0
1
L = 8.2μH
f = 700kHz
10
100 1000
10000
Synchronizing the LT3685 oscillator to an external fre-
quency can be done by connecting a square wave (with
LOAD CURRENT (A)
3685 F05
20% to 80% duty cycle) to the SYNC pin. The square
Figure 5. The Minimum Input Voltage Depends on
Output Voltage, Load Current and Boost Circuit
At light loads, the inductor current becomes discontinu-
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
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT3685, requiring a higher
input voltage to maintain regulation.
Soft-Start
The RUN/SS pin can be used to soft-start the LT3685,
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 6 shows the start-
up and shut-down waveforms with the soft-start circuit.
wave amplitude should have valleys that are below 0.3V
and peaks that are above 0.8V (up to 6V).
The LT3685 may be synchronized over a 250kHz to 2MHz
range. The R T resistor should be chosen to set the LT3685
switching frequency 20% below the lowest synchronization
input. For example, if the synchronization signal will be 250kHz
and higher, the R T should be chosen for 200kHz. To assure
reliable and safe operation the LT3685 will only synchronize
when the output voltage is near regulation as indicated by the
PG ?ag. It is therefore necessary to choose a large enough
inductor value to supply the required output current at the
frequency set by the R T resistor. See Inductor Selection sec-
tion. It is also important to note that slope compensation
is set by the R T value: When the sync frequency is much
higher than the one set by R T , the slope compensation will
be signi?cantly reduced which may require a larger inductor
value to prevent subharmonic oscillation.
3685fb
15
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| LT3686AEDD#PBF | 功能描述:IC REG BUCK ADJ 1.2A 10DFN 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 |
| LT3686AEDD#TRPBF | 功能描述:IC REG BUCK ADJ 1.2A 10DFN 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 |
| LT3686AEMSE#PBF | 功能描述:IC REG BUCK ADJ 1.2A 12MSOP 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:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 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:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
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