- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377969 > ML4771 (Fairchild Semiconductor Corporation) High Current Boost Regulator(高電流升壓穩(wěn)壓器) PDF資料下載
參數(shù)資料
| 型號： | ML4771 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | High Current Boost Regulator(高電流升壓穩(wěn)壓器) |
| 中文描述： | 高電流升壓穩(wěn)壓器（高電流升壓穩(wěn)壓器） |
| 文件頁數(shù)： | 7/8頁 |
| 文件大小： | 265K |
| 代理商： | ML4771 |
ML4771
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
ML4771 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 ML4771 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.
SETTING THE OUTPUT VOLTAGE
The adjustable output of the ML4771 requires an external
feedback resistor divider to set V
OUT
. The output voltage
can be determined from the following equation:
1
6
V
R
R
R
OUT
=
+
257
.
1
2
2
(3)
where R1 and R2 are connected as shown in Figure 2. The
value of R2 should be 250k
W
or less to minimize bias
current errors. Choose an appropriate value for R2 and
calculate R1.
LAYOUT
Good layout practices will ensure the proper operation of
the ML4771. Some layout guidelines follow:
Use adequate ground and power traces or planes
Keep components as close as possible to the ML4771
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 ML4771 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.
DESIGN CONSIDERATIONS
(Continued)
DESIGN EXAMPLE
In order to design a boost converter using the ML4871, 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
.
Then, 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.
Finally, the values of R1 and R2 are calculated using
equation 3, assuming that R2 = 250k
W
:
R
k
k
k
1
50
257
.
250
250
236
=
-
=
.
W
W
W
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
ML4771
100μF
100μF
VIN
10μH
(Sumida CD75)
VL1
VIN
GND
SENSE
PWR GND
NC
VL2
VOUT
250k
236k
VOUT
REV. 1.0 10/10/2000
7
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ML4790 | Adjustable Output, Low Ripple Boost Regulator(輸出可調(diào)、小波紋升壓穩(wěn)壓器) |
| ML4800IP | PCIe-to-PCI-X Reversible Bridge |
| ML4800IS | Power Factor Correction and PWM Controller Combo |
| ML4800CP | Power Factor Correction and PWM Controller Combo |
| ML4800CS | Power Factor Correction and PWM Controller Combo |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4771 / 4871 WAF UP | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4771/ML4871CS UP WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4771CS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Current Boost Regulator |
| ML4771ES | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Current Boost Regulator |
| ML4775 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Adjustable Output Low Voltage Boost Regulator with Shutdown |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。