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參數(shù)資料
| 型號(hào)： | ML4865CS-2 |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類(lèi)： | 穩(wěn)壓器 |
| 英文描述： | High Voltage High Current Boost Regulator |
| 中文描述： | 2 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁(yè)數(shù)： | 7/10頁(yè) |
| 文件大?。?/td> | 126K |
| 代理商： | ML4865CS-2 |
PRODUCT SPECIFICATION
ML4865
REV. 1.0.2 8/10/01
7
The output capacitor’s Equivalent Series Resistance (ESR)
and Equivalent Series Inductance (ESL), also contribute to
the ripple. Just after the NMOS transistor, Q1, turns off, the
current in the output capacitor ramps quickly to between
0.5A and 1.5A. This fast change in current through the
capacitor’s ESL causes a high frequency (5ns) spike to
appear on the output. After the ESL spike settles, the output
still has a ripple component equal to the inductor discharge
current times the ESR. To minimize these effects, choose an
output capacitor with less than 10nH of ESL and 200m
of
ESR.
Suitable tantalum capacitors can be obtained from the fol-
lowing vendors:
AVX
TPS Series
(207) 282-5111
Sprague
593D Series
(207) 324-4140
Kemet
T495 Series
(864) 963-6300
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 22μF to 68μF. This filtering
prevents the input ripple from affecting the ML4865 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 recom-
mended.
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
ML4865 to fail to start-up or to operate unreliably. In gen-
eral, for two cell applications the source impedance should
be less than 200m
, which means that small alkaline cells
should be avoided.
Shutdown
The SHDN pin is a high impedance input and is noise
sensitive. Either drive the SHDN input from a low imped-
ance source or bypass the pin to GND with a 10nF ceramic
capacitor.
Sense
The SENSE pin should be left open or bypassed to ground
for normal operation. The output can be set to voltages lower
than the preset value by adding a resistor divider. The output
voltage can be determined from the following equation:
where R1 and R2 are connected as shown in Figure 2. The
value of R2 should be 1M
or less to minimize bias current
errors. Choose an appropriate value of R2 and calculate the
value of R1.
External Schottky Rectifier
Due to excessive power dissipation, an external Schottky
rectifier is required when operating at input voltages above
6V. Even for applications where the input voltage is below
6V, the use of an external rectifier may be necessary to
achive efficiency or output current requirements.
If an external Schottky is required, look for a device with a
voltage rating of 20V or greater. The average forward current
rating should be at least 500mA, and the forward voltage
should be 600mV or less. Suitable Schottky rectifiers can be
obtained from Fairchild Semiconductor.
Layout
Good layout practices will ensure the proper operation of the
ML4865. Some layout guidelines follow:
Use adequate ground and power traces or planes
Keep components as close as possible to the ML4865
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 ML4865 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 8.
(3)
V
(V)
R1
R2
R2
OUT
=
×
+
2.42
(4)
R2
(
)
V
OUT
2.42
R1
1
=
×
Figure 8. Sample ML4865 Layout
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PDF描述 |
|---|---|
| ML4865 | High Voltage High Current Boost Regulator |
| ML4866 | 3.3V Output DC-DC Step-Down Converter(3.3V輸出的DC-DC步降變換器) |
| ML4869 | Medium Current Boost Regulator with Load Disconnect(負(fù)載可分離的中等電流升壓穩(wěn)壓器) |
| ML4870 | High Current Boost Regulator with Load Disconnect(負(fù)載可分離的大電流升壓穩(wěn)壓器) |
| ML4872 | High Current Boost Regulator with Shutdown(帶關(guān)斷電路的大電流升壓穩(wěn)壓器) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4865CS2X | 功能描述:DC/DC 開(kāi)關(guān)控制器 SOIC-8 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| ML4865ES-2 | 制造商:MICRO-LINEAR 制造商全稱(chēng):MICRO-LINEAR 功能描述:High Voltage High Current Boost Regulator |
| ML4866 | 制造商:MICRO-LINEAR 制造商全稱(chēng):MICRO-LINEAR 功能描述:3.3V Output DC-DC Step-Down Converter |
| ML4866CS | 制造商:MICRO_LINEAR 功能描述: |
| ML4866ES | 制造商:MICRO-LINEAR 制造商全稱(chēng):MICRO-LINEAR 功能描述:3.3V Output DC-DC Step-Down Converter |
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