- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄44983 > LT1912EMSE#PBF (LINEAR TECHNOLOGY CORP) 4.2 A SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO10 PDF資料下載
參數(shù)資料
| 型號： | LT1912EMSE#PBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 4.2 A SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件頁數(shù)： | 24/24頁 |
| 文件大?。?/td> | 365K |
| 代理商： | LT1912EMSE#PBF |
LT1912
9
1912fa
APPLICATIONS INFORMATION
FB Resistor Network
The output voltage is programmed with a resistor divider
between the output and the FB pin. Choose the 1% resis-
tors according to:
R1=R2
VOUT
0.79V
– 1
Reference designators refer to the Block Diagram.
Setting the Switching Frequency
The LT1912 uses a constant frequency PWM architecture
that can be programmed to switch from 200kHz to 500kHz
by using a resistor tied from the RT pin to ground. A table
showing the necessary RT value for a desired switching
frequency is in Figure 1.
SWITCHING FREQUENCY (kHz)
RT VALUE (kΩ)
200
300
400
500
187
121
88.7
68.1
Figure 1. Switching Frequency vs RT Value
Operating Frequency Trade-Offs
Selection of the operating frequency is a trade-off between
efficiency,componentsize,minimumdropoutvoltage,and
maximum input voltage. The advantage of high frequency
operationisthatsmallerinductorandcapacitorvaluesmay
be used. The disadvantages are lower efficiency, lower
maximum input voltage, and higher dropout voltage. The
highest acceptable switching frequency (fSW(MAX)) for a
given application can be calculated as follows:
fSW MAX
(
) =
VD + VOUT
tON MIN
( ) VD + VIN – VSW
(
)
where VIN is the typical input voltage, VOUT is the output
voltage, VD is the catch diode drop (~0.5V) and VSW is the
internal switch drop (~0.5V at max load). This equation
shows that slower switching frequency is necessary to
safely accommodate high VIN/VOUT ratio. Also, as shown
inthenextsection,lowerfrequencyallowsalowerdropout
voltage. The reason input voltage range depends on the
switching frequency is because the LT1912 switch has
finite minimum on and off times. The switch can turn on
for a minimum of ~150ns and turn off for a minimum of
~150ns. Typical minimum on time at 25°C is 80ns. This
means that the minimum and maximum duty cycles are:
DCMIN = fSWtON MIN
( )
DCMAX =1– fSWtOFF MIN
( )
where fSW is the switching frequency, the tON(MIN) is the
minimum switch on time (~150ns), and the tOFF(MIN) is
the minimum switch off time (~150ns). These equations
show that duty cycle range increases when switching
frequency is decreased.
A good choice of switching frequency should allow ad-
equate input voltage range (see next section) and keep
the inductor and capacitor values small.
Input Voltage Range
The maximum input voltage for LT1912 applications
depends on switching frequency, the Absolute Maximum
RatingsoftheVINandBOOSTpins,andtheoperatingmode.
While the output is in start-up, short-circuit, or other
overload conditions, the switching frequency should be
chosen according to the following equation.
VIN MIN
( ) =
VOUT + VD
1– fSWtOFF MIN
( )
– VD + VSW
where VIN(MAX) is the maximum operating input voltage,
VOUT is the output voltage, VD is the catch diode drop
(~0.5V), VSW is the internal switch drop (~0.5V at max
load), fSW is the switching frequency (set by RT), and
tON(MIN)istheminimumswitchontime(~150ns).Notethat
a higher switching frequency will depress the maximum
operating input voltage. Conversely, a lower switching
frequency will be necessary to achieve safe operation at
high input voltages.
If the output is in regulation and no short-circuit, start-
up, or overload events are expected, then input voltage
transients of up to 36V are acceptable regardless of the
switching frequency. In this mode, the LT1912 may enter
相關PDF資料 |
PDF描述 |
|---|---|
| LT1932ES6#TRM | 0.78 A SWITCHING REGULATOR, 1600 kHz SWITCHING FREQ-MAX, PDSO6 |
| LT1933HDCB#TRM | 1.05 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO6 |
| LT1933HDCB | 1.05 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO6 |
| LT1933HS6 | 1.05 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO6 |
| LT1933IDCB#PBF | 1.05 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO6 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LT1912EMSE-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:36V, 2A, 500kHz Step-Down Switching Regulator |
| LT1913 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:25V, 3.5A, 2.4MHz Step-Down Switching Regulator |
| LT1913EDD#PBF | 功能描述:IC REG BUCK ADJ 3.5A 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 標準包裝:250 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:1.2V 輸入電壓:2.05 V ~ 6 V PWM 型:電壓模式 頻率 - 開關:2MHz 電流 - 輸出:500mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:6-UFDFN 包裝:帶卷 (TR) 供應商設備封裝:6-SON（1.45x1） 產(chǎn)品目錄頁面:1032 (CN2011-ZH PDF) 其它名稱:296-25628-2 |
| LT1913EDD#TRPBF | 功能描述:IC REG BUCK ADJ 3.5A 10DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 設計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應商設備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT1913EDD-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:25V, 3.5A, 2.4MHz Step-Down Switching Regulator |
發(fā)布緊急采購，3分鐘左右您將得到回復。