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| 型号： | LT3970EMS#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/22页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 0.35A 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： | 1.21 V ~ 25 V |
| 输入电压： | 4.2 V ~ 40 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 200kHz ~ 2.25MHz |
| 电流 - 输出： | 350mA |
| 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） |
| 包装： | 管件 |
| 供应商设备封装： | 10-MSOP |
| 产品目录页面： | 1332 (CN2011-ZH PDF) |
LT3970 Series
APPLICATIONS INFORMATION
V IN
V IN
BD
BOOST
V OUT
5.0
4.5
FRONT PAGE APPLICATION
V OUT = 3.3V
LT3970
C3
GND
SW
4.0
TO START/RUN
3.5
(4a) For V OUT ≥ 2.2V
3.0
BD
2.5
0
50
100
150
200
250
300
350
V IN
V IN
BOOST
LOAD CURRENT (mA)
LT3970
GND
SW
C3
V OUT
6.5
6.0
FRONT PAGE APPLICATION
V OUT = 5V
TO START
(4b) For V OUT < 2.2V; V IN < 27V
3970 F04
5.5
TO RUN
V IN(EN) =
R3 + R4
Figure4.TwoCircuitsforGeneratingtheBoostVoltage
If the input voltage is ramped slowly, the boost capacitor
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 5 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
of the BOOST pin.
Enable Pin
The LT3970 is in shutdown when the EN pin is low and
active when the pin is high. The rising threshold of the EN
comparator is 1V, with a 30mV hysteresis. This threshold
is accurate when V IN is above 4.2V. If V IN is lower than
4.2V, tie EN pin to GND to place the part in shutdown.
14
5.0
4.5
4.0
0 50 100 150 200 250 300 350
LOAD CURRENT (mA) 3970 F05
Figure 5. The Minimum Input Voltage Depends on
Output Voltage, Load Current and Boost Circuit
Adding a resistor divider from V IN to EN programs the
LT3970 to regulate the output only when V IN is above a
desired voltage (see Figure 6). This threshold voltage,
V IN(EN) , can be adjusted by setting the values R3 and R4
such that they satisfy the following equation:
? 1V
R4
where output regulation should not start until V IN is above
V IN(EN) . Note that due to the comparator’s hysteresis,
regulation will not stop until the input falls slightly below
V IN(EN) .
3970fc
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相关代理商/技术参数 |
参数描述 |
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| LT3970EMS-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:40V, 350mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes |
| LT3970HMS#PBF | 制造商:Linear Technology 功能描述:IC REG BUCK ADJ 0.35A 10MSOP 制造商:Linear Technology 功能描述:IC, STEP DOWN REG, 200KHZ-2.2MHZ, MSOP10 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, MSOP10, Primary Input Voltage:40V, No. of Outputs:1, Output Current:350mA, No. of Pins:10, Operating Temperature Min:-40C, Operating Temperature Max:150C, Package / Case:10-MSOP , RoHS Compliant: Yes |
| LT3970HMS#TRPBF | 制造商:Linear Technology 功能描述:IC REG BUCK ADJ 0.35A 10MSOP 制造商:Linear Technology 功能描述:SWITCHING REG, BUCK, ADJ, 2.2MHZ, MSOP10, Primary Input Voltage:40V, No. of Outputs:1, Output Current:350mA, No. of Pins:10, Operating Temperature Min:-40C, Operating Temperature Max:150C, Package / Case:10-MSOP , RoHS Compliant: Yes |
| LT3970HMS-3.3#PBF | 功能描述:IC REG BUCK 3.3V 0.35A 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 |
| LT3970HMS-3.3#TRPBF | 功能描述:IC REG BUCK 3.3V 0.35A 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 |
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