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参数资料
| 型号： | LT3470HDDB |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 0.2 A SWITCHING REGULATOR, PDSO8 |
| 封装： | 3 X 2 MM, 0.75MM INCH HEIGHT, MO-229WECD-1, PLASTIC, DFN-8 |
| 文件页数： | 4/20页 |
| 文件大小： | 256K |
| 代理商： | LT3470HDDB |
12
LT3470
3470fc
(Figure 2b). The circuit in Figure 2a is more efficient
because the BOOST pin current and BIAS pin quiescent
current comes from a lower voltage source. You must also
be sure that the maximum voltage ratings of the BOOST
and BIAS pins are not exceeded.
The minimum operating voltage of an LT3470 application
is limited by the undervoltage lockout (4V) and by the
maximum duty cycle as outlined in a previous section. For
proper start-up, the minimum input voltage is also limited
by the boost circuit. If the input voltage is ramped slowly,
or the LT3470 is turned on with its SHDN pin when the
output is already in regulation, then the boost capacitor
may not be fully charged. The plots in Figure 3 show
minimum VIN to start and to run. At light loads, the
inductor current becomes discontinuous and the effective
duty cycle can be very high. This reduces the minimum
input voltage to approximately 300mV above VOUT. At
higher load currents, the inductor current is continuous
and the duty cycle is limited by the maximum duty cycle of
the LT3470, requiring a higher input voltage to maintain
regulation.
Shorted Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively at the top switch current limit maximum of 450mA,
an LT3470 buck regulator will tolerate a shorted output
even if VIN = 40V. There is another situation to consider in
systems where the output will be held high when the input
to the LT3470 is absent. This may occur in battery charg-
ing applications or in battery backup systems where a
battery or some other supply is diode OR-ed with the
LT3470’s output. If the VIN pin is allowed to float and the
SHDN pin is held high (either by a logic signal or because
it is tied to VIN), then the LT3470’s internal circuitry will
pull its quiescent current through its SW pin. This is fine
if your system can tolerate a few mA in this state. If you
ground the SHDN pin, the SW pin current will drop to
essentially zero. However, if the VIN pin is grounded while
the output is held high, then parasitic diodes inside the
LT3470 can pull large currents from the output through
the SW pin and the VIN pin. Figure 4 shows a circuit that
will run only when the input voltage is present and that
protects against a shorted or reversed input.
Minimum Input Voltage, VOUT = 3.3V
Minimum Input Voltage, VOUT = 5V
Figure 3. The Minimum Input Voltage Depends on Output
Voltage, Load Current and Boost Circuit
Figure 4. Diode D1 Prevents a Shorted Input from Discharging a
Backup Battery Tied to the Output; It Also Protects the Circuit
from a Reversed Input. The LT3470 Runs Only When the Input is
Present Hot-Plugging Safely
VIN
BOOST
LT3470 SOT-23
SW
SHDN
3470 F04
VIN
100k
D1
1M
VOUT
BACKUP
BIAS
FB
GND
APPLICATIO S I FOR ATIO
WU
UU
LOAD CURRENT (mA)
0
3.0
INPUT
VOLTAGE
(V)
3.5
4.0
4.5
5.0
5.5
6.0
50
100
150
200
3470 G18
TA = 25°C
VIN TO START
VIN TO RUN
LOAD CURRENT (mA)
0
INPUT
VOLTAGE
(V)
6
7
200
3470 G19
5
4
50
100
150
8
TA = 25°C
VIN TO START
VIN TO RUN
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3470HDDB#TRMPBF | 功能描述:IC REG BUCK ADJ 0.2A 8DFN 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 |
| LT3470HDDB#TRPBF | 功能描述:IC REG BUCK ADJ 0.2A 8DFN 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 |
| LT3470HTS8 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Buck Regulator with Integrated Boost and Catch Diodes |
| LT3470HTS8#PBF | 制造商:Linear Technology 功能描述:SP-SWREG/Monolithic, Cut Tape 300mA, 40V MicroPower Step-Down Regulator with Int |
| LT3470HTS8#TRMPBF | 功能描述:IC REG BUCK ADJ 0.2A TSOT23-8 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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