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| 型号： | LT3493EDCB#TRM |
| 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： | 3/20页 |
| 文件大小： | 588K |
| 代理商： | LT3493EDCB#TRM |
LT3493
11
3493fb
APPLICATIONS INFORMATION
capacitor must be large to achieve low ESR. Table 2 lists
several capacitor vendors.
Figure 4 shows the transient response of the LT3493 with
several output capacitor choices. The output is 3.3V. The
load current is stepped from 250mA to 1A and back to
250mA, and the oscilloscope traces show the output volt-
age. The upper photo shows the recommended value. The
second photo shows the improved response (less voltage
drop) resulting from a larger output capacitor and a phase
lead capacitor. The last photo shows the response to a high
performance electrolytic capacitor. Transient performance
is improved due to the large output capacitance.
BOOST Pin Considerations
Capacitor C3 and diode D2 are used to generate a boost
voltage that is higher than the input voltage. In most cases
a 0.1μF capacitor and fast switching diode (such as the
1N4148 or 1N914) will work well. Figure 5 shows two
ways to arrange the boost circuit. The BOOST pin must
be at least 2.3V above the SW pin for best efciency. For
outputs of 3.3V and above, the standard circuit (Figure 5a)
is best. For outputs between 3V and 3.3V, use a 0.22μF
capacitor. For outputs between 2.5V and 3V, use a 0.47μF
capacitor and a small Schottky diode (such as the BAT-
54). For lower output voltages the boost diode can be tied
to the input (Figure 5b). The circuit in Figure 5a is more
efcient because the BOOST pin current comes from a lower
voltage source. You must also be sure that the maximum
voltage rating of the BOOST pin is not exceeded.
The minimum operating voltage of an LT3493 applica-
tion is limited by the undervoltage lockout (3.6V) and by
the maximum duty cycle as outlined above. For proper
start-up, the minimum input voltage is also limited by
the boost circuit. If the input voltage is ramped slowly,
or the LT3493 is turned on with its SHDN pin when the
output 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. Figure 6 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 VIN
is ramping verly slowly. For lower start-up voltage, the
boost diode can be tied to VIN; however this restricts the
input range to one-half of the absolute maximum rating
of the BOOST pin.
Table 2. Capacitor Vendors
VENDOR
PHONE
URL
PART SERIES COMMENTS
Panasonic
(714) 373-7366
www.panasonic.com
Ceramic,
Polymer,
Tantalum
EEF Series
Kemet
(864) 963-6300
www.kemet.com
Ceramic,
Tantalum
T494, T495
Sanyo
(408) 749-9714
www.sanyovideo.com
Ceramic,
Polymer,
Tantalum
POSCAP
Murata
(404) 436-1300
www.murata.com
Ceramic
AVX
www.avxcorp.com
Ceramic,
Tantalum
TPS Series
Taiyo Yuden
(864) 963-6300
www.taiyo-yuden.com
Ceramic
相关PDF资料 |
PDF描述 |
|---|---|
| LT3493EDCB#TR | 2.2 A SWITCHING REGULATOR, 815 kHz SWITCHING FREQ-MAX, PDSO6 |
| LT3513EUHF#TRPBF | 3.5 A SWITCHING REGULATOR, 2220 kHz SWITCHING FREQ-MAX, PQCC38 |
| LT3513EUHF#PBF | 3.5 A SWITCHING REGULATOR, 2220 kHz SWITCHING FREQ-MAX, PQCC38 |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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 |
| LT3493IDCB | 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 |
| LT3493IDCB#PBF | 制造商:Linear Technology 功能描述:BUCK SW REG 1.4A 750KHZ 6D 制造商:Linear Technology 功能描述:DC-DC CONVERTER BUCK 750KHZ 制造商:Linear Technology 功能描述:BUCK, SW REG, 1.4A, 750KHZ, 6DFN 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, 750KHZ, 1.2A, DFN-6; Primary Input Voltage:36V; No. of Outputs:1; Output Voltage:780mV; Output Current:1.2A; No. of Pins:6; Operating Temperature Min:-40C; Operating Temperature Max:125C; Package / Case:6-DFN;RoHS Compliant: Yes |
| LT3493IDCB#PBF | 制造商:Linear Technology 功能描述:DC-DC CONVERTER, BUCK, 750KHZ, 1.2A, DFN |
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