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參數(shù)資料
| 型號： | ML4861 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Low Voltage Drop Boost Regulator(低壓差升壓穩(wěn)壓器) |
| 中文描述： | 低壓降升壓穩(wěn)壓器（低壓差升壓穩(wěn)壓器） |
| 文件頁數(shù)： | 8/11頁 |
| 文件大小： | 118K |
| 代理商： | ML4861 |
ML4861
8
REV. 1.0 10/12/2000
INPUT CAPACITOR
Unless the input source is a very low impedance battery,
it will be necessary to decouple the input with a
capacitor with a value of between 47μF and 100μF. This
provides the benefits of preventing input ripple from
affecting the ML4861 control circuitry, and it also
improves efficiency by reducing I-squared R losses during
the charge and discharge cycles of the inductor. Again, a
low ESR capacitor (such as tantalum) is recommended.
REFERENCE CAPACITOR
Under some circumstances input ripple cannot be reduced
effectively. This occurs primarily in applications where
inductor currents are high, causing excess output ripple
due to “pulse grouping”, where the charge-discharge
pulses are not evenly spaced in time. In such cases it may
be necessary to decouple the reference pin (V
REF
) with a
small 10nF to 100nF ceramic capacitor. This is
particularly true if the ripple voltage at V
IN
is greater than
100mV.
SETTING THE
RESET
THRESHOLD
To use the
RESET
comparator as an input voltage
monitor, it is necessary to use an external resistor divider
tied to the DETECT pin as shown in the block diagram.
The resistor values R
A
and R
B
can be calculated using the
following equation:
V
R
(
R
R
IN MIN
(
A
B
B
)
.
)
=
×
+
0 2
(5)
The value of R
B
should be 100ky or less to minimize bias
current errors. R
A
is then found by rearranging the
equation:
R
R
V
A
B
IN MIN
(
.2
=
×
)
1
(6)
LAYOUT
Good PC board layout practices will ensure the proper
operation of the ML4861. Important layout considerations
include:
Use adequate ground and power traces or planes
Keep components as close as possible to the ML4861
Use short trace lengths from the inductor to the V
L
pin
and from the output capacitor to the V
OUT
pin
Use a single point ground for the ML4861 ground pins,
and the input and output capacitors
A sample PC board layout is shown in Figure 6.
TOP LAYER
BOTTOM LAYER
Figure 6. Sample PC Board Layout.
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| ML4861CS-3 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Low Voltage Boost Regulator |
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