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參數(shù)資料
| 型號： | LM2733XMFX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.6/1.6 MHz Boost Converters With 40V Internal FET |
| 中文描述： | 1.5 A SWITCHING REGULATOR, 1850 kHz SWITCHING FREQ-MAX, PDSO5 |
| 封裝： | SOT-23, 5 PIN |
| 文件頁數(shù)： | 12/13頁 |
| 文件大?。?/td> | 507K |
| 代理商： | LM2733XMFX |
Application Hints
(Continued)
The maximum peak switch current the device can deliver is
dependent on duty cycle. The minimum value is guaranteed
to be
>
1A at duty cycle below 50%. For higher duty cycles,
see Typical performance Characteristics curves.
THERMAL CONSIDERATIONS
At higher duty cycles, the increased ON time of the FET
means the maximum output current will be determined by
power dissipation within the LM2733 FET switch. The switch
power dissipation from ON-state conduction is calculated by:
P
(SW)
= DC x I
IND
(AVE)
2
x R
DS
ON
There will be some switching losses as well, so some derat-
ing needs to be applied when calculating IC power dissipa-
tion.
MINIMUM INDUCTANCE
In some applications where the maximum load current is
relatively small, it may be advantageous to use the smallest
possible inductance value for cost and size savings. The
converter will operate in discontinuous mode in such a case.
The minimum inductance should be selected such that the
inductor (switch) current peak on each cycle does not reach
the 1A current limit maximum. To understand how to do this,
an example will be presented.
In the example, the LM2733X will be used (nominal switch-
ing frequency 1.6 MHz, minimum switching frequency
1.15 MHz). This means the maximum cycle period is the
reciprocal of the minimum frequency:
T
ON(max)
= 1/1.15M = 0.870 μs
We will assume the input voltage is 5V, V
OUT
= 12V, V
SW
=
0.2V, V
DIODE
= 0.3V. The duty cycle is:
Duty Cycle = 60.3%
Therefore, the maximum switch ON time is 0.524 μs. An
inductor should be selected with enough inductance to pre-
vent the switch current from reaching 1A in the 0.524 μs ON
time interval (see below):
20055413
Discontinuous Design, 5V–12V Boost (LM2733X)
The voltage across the inductor during ON time is 4.8V.
Minimum inductance value is found by:
V = L X dl/dt, L = V X (dt/dl) = 4.8 (0.524μ/1) = 2.5 μH
In this case, a 2.7 μH inductor could be used assuming it
provided at least that much inductance up to the 1A current
value. This same analysis can be used to find the minimum
inductance for any boost application. Using the slower
switching “Y” version requires a higher amount of minimum
inductance because of the longer switching period.
INDUCTOR SUPPLIERS
Some of the recommended suppliers of inductors for this
product include, but not limited to are Sumida, Coilcraft,
Panasonic, TDK and Murata. When selecting an inductor,
make certain that the continuous current rating is high
enough to avoid saturation at peak currents. A suitable core
type must be used to minimize core (switching) losses, and
wire power losses must be considered when selecting the
current rating.
SHUTDOWN PIN OPERATION
The device is turned off by pulling the shutdown pin low. If
this function is not going to be used, the pin should be tied
directly to V
. If the SHDN function will be needed, a pull-up
resistor must be used to V
(approximately 50k-100k
rec-
ommended). The SHDN pin must not be left unterminated.
L
www.national.com
12
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2733XMFX/NOPB | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 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 安裝風格: 封裝 / 箱體:CPAK |
| LM2733XMFX-NOPB | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LM2733 0.6/1.6 MHz Boost Converters With 40V Internal FET Switch in SOT-23 |
| LM2733YEVAL | 功能描述:電源管理IC開發(fā)工具 LM2733Y EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM2733YEVAL/NOPB | 功能描述:電源管理IC開發(fā)工具 LM2733Y EVAL BOARD RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類型:Battery Management 工具用于評估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V |
| LM2733YMF | 功能描述:DC/DC 開關控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開關頻率: 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 安裝風格: 封裝 / 箱體:CPAK |
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