参数资料
| 型号： | LT3493IDCB#TRMPBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/20页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 1.2A 6DFN |
| 标准包装： | 500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.78 V ~ 34.2 V |
| 输入电压： | 3.6 V ~ 36 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 750kHz |
| 电流 - 输出： | 1.2A |
| 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： | 6-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 6-DFN-EP（2x3） |
LT3493
APPLICATIONS INFORMATION
7.5
7.0
TO START
5.5
5.3
5.1
4.9
6.5
6.0
5.5
5.0
TO RUN
4.7
4.5
4.3
4.1
3.9
3.7
3.5
TO RUN
TO START
1
10
100
1000
1
10
100
1000
I OUT (mA)
3493 G15
I OUT (mA)
3493 G16
(6a) Typical Minimum Input Voltage, V OUT = 5V
Figure 6
(6b) Typical Minimum Input Voltage, V OUT = 3.3V
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
400mV 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 LT3493, requiring a higher
input voltage to maintain regulation.
Soft-Start
The SHDN pin can be used to soft-start the LT3493, reducing
the maximum input current during start-up. The SHDN pin
is driven through an external RC ?lter to create a voltage
ramp at this pin. Figure 7 shows the start-up waveforms
with and without 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 SHDN pin reaches 2.3V.
Shorted and Reversed Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively, an LT3493 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
LT3493 is absent. This may occur in battery charging ap-
plications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT3493’s
output. If the V IN pin is allowed to ?oat and the SHDN pin
is held high (either by a logic signal or because it is tied
to V IN ), then the LT3493’s internal circuitry will pull its
quiescent current through its SW pin. This is ?ne 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 V IN pin is grounded while the output
is held high, then parasitic diodes inside the LT3493 can
pull large currents from the output through the SW pin
and the V IN pin. Figure 8 shows a circuit that will run only
when the input voltage is present and that protects against
a shorted or reversed input.
Hot Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LT3493 circuits. However, these capaci-
tors can cause problems if the LT3493 is plugged into a
live supply (see Linear Technology Application Note 88 for
3493fb
13
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相关代理商/技术参数 |
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| LT3493IDCB-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.2A, 750kHz Step-Down Switching Regulator in 2mm × 3mm DFN |
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| LT3494AEDDB | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower Low Noise Boost Converters with Output Disconnect |
| LT3494AEDDB#PBF | 制造商:Linear Technology 功能描述:BOOST 2.3 - 16V 0.35A 40V 制造商:Linear Technology 功能描述:BOOST, 2.3 - 16V, 0.35A, 40V, 20QFN |
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