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参数资料
| 型号： | LT3500IMSE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3.5 A SWITCHING REGULATOR, 2800 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 8/28页 |
| 文件大小： | 318K |
| 代理商： | LT3500IMSE#PBF |
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LT3500
16
3500fc
the value of output capacitance required. Also, the current
mode control loop doesn’t require the presence of output
capacitor series resistance (ESR). For these reasons, you
are free to use ceramic capacitors to achieve very low
output ripple and small circuit size. Estimate output ripple
with the following equations:
V
RIPPLE =
ΔI
L
8 Frequency C
OUT1
For ceramic capacitors and,
VRIPPLE = IL ESR
For electrolytic (tantalum and aluminum)
where
IL is the peak-to-peak ripple current in the
inductor.
The RMS content of this ripple is very low, and the RMS
current rating of the output capacitor is usually not of
concern.
Another constraint on the output capacitor is that it must
have greater energy storage than the inductor; if the stored
energy in the inductor is transferred to the output, you
would like the resulting voltage step to be small compared
to the regulation voltage. For a 5% overshoot, this require-
ment becomes:
COUT1>10 L
ILIM
VOUT1
2
Finally, there must be enough capacitance for good transient
performance. The last equation gives a good starting point.
Alternatively, you can start with one of the designs in this
data sheet and experiment to get the desired performance.
This topic is covered more thoroughly in the section on
loop compensation.
The high performance (low ESR), small size and robust-
ness of ceramic capacitors make them the preferred type
for LT3500 applications. However, all ceramic capacitors
are not the same. As mentioned above, many of the high
value capacitors use poor dielectrics with high tempera-
ture and voltage coefcients. In particular, Y5V and Z5U
types lose a large fraction of their capacitance with ap-
plied voltage and temperature extremes. Because the loop
stability and transient response depend on the value of
COUT1, you may not be able to tolerate this loss. Use X7R
and X5R types. You can also use electrolytic capacitors.
The ESRs of most aluminum electrolytics are too large to
deliver low output ripple. Tantalum and newer, lower ESR
organic electrolytic capacitors intended for power supply
use, are suitable and the manufacturers will specify the
ESR. The choice of capacitor value will be based on the
ESR required for low ripple. Because the volume of the
capacitor determines its ESR, both the size and the value
will be larger than a ceramic capacitor that would give you
similar ripple performance. One benet is that the larger
capacitance may give better transient response for large
changes in load current.
Catch Diode
The diode D1 conducts current only during switch off
time. Use a Schottky diode to limit forward voltage drop to
increase efciency. The Schottky diode must have a peak
reverse voltage that is equal to regulator input voltage and
sized for average forward current in normal operation.
Average forward current can be calculated from:
I
D(AVG) =
I
OUT1
V
IN
V
IN VOUT1
()
APPLICATIONS INFORMATION
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| LT1304CS8-5#PBF | 1.2 A SWITCHING REGULATOR, 300 kHz SWITCHING FREQ-MAX, PDSO8 |
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相关代理商/技术参数 |
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|---|---|
| LT3500IMSE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic 2A Step-Down Regulator Plus Linear Regulator/Controller |
| LT3500T | 制造商:Eaton Corporation 功能描述:TYPE LT TRIP UNIT ONLY 3P 500A 600VAC MAX |
| LT3501 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic Dual Tracking 3A Step-Down Switching Regulator |
| LT3501_12 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Monolithic Dual Tracking 3A Step-Down Switching |
| LT3501EFE | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step Down 3.1V to 25V 20-Pin TSSOP EP |
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