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参数资料
| 型号： | LT3493EDCB-3#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2.2 A SWITCHING REGULATOR, 815 kHz SWITCHING FREQ-MAX, PDSO6 |
| 封装： | 2 X 3 MM, PLASTIC, MO-229, DFN-6 |
| 文件页数： | 5/20页 |
| 文件大小： | 401K |
| 代理商： | LT3493EDCB-3#TR |
13
LT3493-3
3493-3f
RUN
VSW
10V/DIV
VIN = 12V
VOUT = 3.3V
L = 10
H
COUT = 10F
VOUT
2V/DIV
20
s/DIV
IL
0.5A/DIV
VSW
10V/DIV
VIN = 12V
VOUT = 3.3V
L = 10
H
COUT = 10F
VOUT
2V/DIV
20
s/DIV
IL
0.5A/DIV
SHDN
GND
3493-3 F07a
RUN
15k
0.1
F
SHDN
GND
3493-3 F07b
is already in regulation, then 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 the
input and output voltages, and on the arrangement of the
boost circuit. The minimum load generally goes to zero
once the circuit has started. In many cases the discharged
output capacitor will present a load to the switcher which
will allow it to start. For 3.3V applications, the undervolt-
age lockout is high enough (6.8V) that the boost capacitor
always gets charged. For 5V applications with output
loads less than 20mA, the minimum input voltage required
to charge the boost capacitor is 6.8V. Note this higher
input voltage requirements is only in worst-case situation
where VIN is being ramped very slowly. For lower start-up
voltage, the boost diode can be tied to VIN; however this
APPLICATIO S I FOR ATIO
WU
U
restricts the input range to one-half of the absolute maxi-
mum rating of the BOOST pin.
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 VOUT. At higher load currents, the inductor
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT3493-3, requiring a higher
input voltage to maintain regulation.
Soft-Start
The SHDN pin can be used to soft-start the LT3493-3,
reducing the maximum input current during start-up. The
SHDN pin is driven through an external RC filter to create
a voltage ramp at this pin. Figure 6 shows the start-up
waveforms with and without the soft-start circuit. By
Figure 6. To Soft-Start the LT3493-3, Add a Resistor and Capacitor to the SHDN pin. VIN = 12V, VOUT = 3.3V, COUT = 10F, RLOAD = 5
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相关代理商/技术参数 |
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| LT3493EDCBPBF | 制造商:LT 功能描述:Pb Free |
| LT3493EDCB-PBF | 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 |
| LT3493EDCB-TR | 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 |
| LT3493EDCBTRMPBF | 制造商:Linear Technology 功能描述:Sw. Regulator 1.2A 750kHz Step-Down DFN6 |
| LT3493EDCB-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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