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參數(shù)資料
| 型號： | MCP1612 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | Single 1A, 1.4 MHz Synchronous Buck Regulator |
| 中文描述： | 單1A條，1.4 MHz的同步降壓穩(wěn)壓器 |
| 文件頁數(shù)： | 12/22頁 |
| 文件大小： | 230K |
| 代理商： | MCP1612 |
MCP1612
DS21921B-page 12
2005 Microchip Technology Inc.
5.2.2
BUCK INDUCTOR
There are many requirements that need to be satisfied
when selecting the buck inductor. The application,
physical size, current rating, resistance, mounting
method, supplier, temperature range, minimum
inductance and cost all need to be considered.
Many suppliers specify the maximum peak current that
an inductor can handle before magnetic saturation
occurs. The peak current is equal to the maximum DC
output current, plus one-half the peak-to-peak AC
ripple current.
When the P-channel MOSFET is on, the current in the
buck inductor is ramped up. The voltage across the
inductor, the inductance and the MOSFET on-time are
required to determine the peak-to-peak ripple current.
When operating in Continuous Current mode, the on-
time of the P-channel MOSFET is determined by
multiplying the duty cycle by the switching period. The
following equation can be used to determine the duty
cycle.
EQUATION 5-2:
The on-time is then defined as follows.
EQUATION 5-3:
The AC ripple current in the inductor can be calculated
by the following relationship.
EQUATION 5-4:
Solving for
Δ
I
L
yields:
EQUATION 5-5:
The value of the buck inductor is chosen to be 3.3 μH.
The AC ripple current is controlled by the size of the
buck inductor. The value of the inductor will therefore
need to be raised so that the converter operates in
Continuous Conduction mode. Calculation of the buck
inductor current rating follows.
The inductor selected must have an inductance of
3.3 μH at a peak current rating of 1.08A. The DC resis-
tance of the inductor should be as low as is feasibly
possible. Extremely low DC resistance inductors are
available, though a trade-off between size and cost
should be considered.
5.2.3
OUTPUT CAPACITOR
The output capacitor is used to filter the inductor AC
ripple current and provide storage for load transients.
The size and Equivalent Series Resistance (ESR) of
the output capacitor determines the amount of ripple
voltage present at the output of the converter. When
selecting the output capacitor, a design trade-off has to
be made between the acceptable ripple voltage and the
size/cost of the output capacitor. Ceramic capacitors
have very low ESR, but increase in cost with higher
values. Tantalum and electrolytic capacitors are
relatively inexpensive in higher values, but they also
have a much higher ESR.
The amount of capacitance needed to obtain the
desired ripple voltage is calculated by using the
following relationship.
EQUATION 5-6:
DutyCycle
V
V
IN
-------------
=
T
ON
DutyCycle
F
SW
---------
×
=
Where:
F
SW
= switching frequency
V
L
L
Δ
I
L
t
--------
×
=
Δ
I
L
V
L
L
-----
Δ
t
×
=
Where:
V
L
= voltage across the inductor
(V
IN
– V
OUT
)
Δ
t = on-time of the P-channel MOSFET
V
IN
= 3.3V
V
OUT
= 1.2V
F
SW
= 1.4 MHz
I
OUT(MAX)
= 1A
T
ON
= (1.2V/3.3V) x (1/1.4 MHz)
T
ON
= 260 ns
V
L
= (3.3V – 1.2V) = 2.1V
Δ
I
L
= (2.1V/3.3 μH) x 260 ns
Δ
I
L
= 165 mA
I
L(PEAK)
= I
OUT(MAX)
+ 1/2
Δ
I
L
I
L(PEAK)
= 1A + (165 mA)/2
I
L(PEAK)
= 1.08A
I
C
C
Δ
V
C
t
----------
×
=
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相關(guān)代理商/技術(shù)參數(shù) |
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| MCP1612_13 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:Single 1A, 1.4 MHz Synchronous Buck Regulator |
| MCP1612-120I/MS | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 1.4MHz 1A Synch-Buck RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| MCP1612-150I/MS | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 1.4MHz 1A Synch-Buck RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| MCP1612-180I/MS | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 1.4MHz 1A Synch-Buck RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| MCP1612-250I/MS | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 1.4MHz 1A Synch-Buck RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
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