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參數(shù)資料
| 型號： | ML4872 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | High Current Boost Regulator with Shutdown(帶關斷電路的大電流升壓穩(wěn)壓器) |
| 中文描述： | 高電流升壓關斷穩(wěn)壓器（帶關斷電路的大電流升壓穩(wěn)壓器） |
| 文件頁數(shù)： | 7/9頁 |
| 文件大?。?/td> | 196K |
| 代理商： | ML4872 |
7
ML4872
INPUT CAPACITOR
Due to the high input current drawn at startup and
possibly during operation, it is recommended to decouple
the input with a capacitor with a value of 47μF to 100μF.
This filtering prevents the input ripple from affecting the
ML4872 control circuitry, and also improves the
efficiency by reducing the I squared R losses during the
charge cycle of the inductor. Again, a low ESR capacitor
(such as tantalum) is recommended.
It is also recommended that low source impedance
batteries be used. Otherwise, the voltage drop across the
source impedance during high input current situations will
cause the ML4872 to fail to start-up or to operate
unreliably. In general, for two cell applications the source
impedance should be less than 200m
W
, which means that
small alkaline cells should be avoided.
LAYOUT
Good layout practices will ensure the proper operation of
the ML4872. Some layout guidelines follow:
Use adequate ground and power traces or planes
Keep components as close as possible to the ML4872
Use short trace lengths from the inductor to the V
L1
and
V
L2
pins and from the output capacitor to the V
OUT
pin
Use a single point ground for the ML4872 ground pin,
and the input and output capacitors
Separate the ground for the converter circuitry from the
ground of the load circuitry and connect at a single
point
A sample layout is shown in Figure 7.
Figure 7. Sample PC Board Layout
DESIGN CONSIDERATIONS
(Continued)
DESIGN EXAMPLE
In order to design a boost converter using the ML4872, it
is necessary to define a few parameters. For this example,
assume that V
IN
= 3.0V to 3.6V, V
OUT
= 5.0V, and
I
OUT(MAX)
= 500mA.
First, it must be determined whether the ML4871 is
capable of delivering the output current. This is done
using Equation 1:
I
V
V
A
A
OUT MAX
(
)
.
.
.
.
.
=
=
125
30
50
07
053
Next, select an inductor. As previously mentioned, the
recommended inductance is 10μH. Make sure that the
peak current rating of the inductor is at least 1.5A, and
that the DC resistance of the inductor is in the range of 50
to 100m
W
.
Finally, the value of the output capacitor is determined
using Equation 2:
C
H
V
F
OUT
=
50
.
=
44 10
88
m
m
The closest standard value would be a 100μF capacitor
with an ESR rating of 100m
W
. If such a low ESR value
cannot be found, two 47μF capacitors in parallel could
also be used.
The complete circuit is shown in Figure 8. As mentioned
previously, the use of an input supply bypass capacitor is
highly recommended.
Figure 8. Typical Application Circuit
ML4872
VOUT
100μF
100μF
VIN
10μH
(Sumida CD75)
VL1
VIN
GND
SHDN
PWR GND
NC
VL2
VOUT
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|---|---|
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ML4872CS3 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ML4872CS-3 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Current Boost Regulator with Shutdown |
| ML4872CS3X | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ML4872CS5 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ML4872CS-5 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Current Boost Regulator with Shutdown |
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