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參數(shù)資料
| 型號： | LT1949-1EMS8 |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 1.5 A SWITCHING REGULATOR, 1350 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封裝： | PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 5/8頁 |
| 文件大?。?/td> | 222K |
| 代理商： | LT1949-1EMS8 |
5
LT1949-1
BLOCK DIAGRA
W
–
+
–
+
–
+
–
+
–
+
Σ
RAMP
GENERATOR
1.24V
REFERENCE
R
BIAS
VC
gm
FB
ENABLE
200mV
A = 2
FF
A1
COMPARATOR
A2
COMPARATOR
ERROR
AMPLIFIER
A4
0.06
DRIVER
SW
GND
1949-1 BD
Q3
Q
S
1.1MHz
OSCILLATOR
5
LBO
LBI
SHDN
SHUTDOWN
3
7
1
4
R1
(EXTERNAL)
VOUT
8
R2
(EXTERNAL)
FB
2
Figure 3. LT1949-1 Block Diagram
The LT1949-1 is a current mode, fixed frequency step-up
DC/DC converter with an internal 1A NPN power transis-
tor. Operation can best be understood by referring to the
Block Diagram.
At the beginning of each oscillator cycle, the flip-flop is set
and the switch is turned on. Current in the switch ramps
up until the voltage at A2’s positive input reaches the VC
pin voltage, causing A2’s output to change state and the
switch to be turned off. The signal at A2’s positive input is
a summation of a signal representing switch current and
a ramp generator (introduced to avoid subharmonic oscil-
lations at duty factors greater than 50%). If the load
increases, VOUT (and FB) will drop slightly and the error
amplifier will drive VC to a higher voltage, causing current
in the switch to increase. In this way, the error amplifier
drives the VC pin to the voltage necessary to satisfy the
load. Frequency compensation is provided by an external
series RC network connected between the VC pin and
ground.
Layout Hints
The LT1949-1 switches current at high speed, mandating
careful attention to layout for proper performance.
You
will not get advertised performance with careless layouts.
Figure 4 shows recommended component placement for
a boost (step-up) converter. Follow this closely in your PC
layout. Note the direct path of the switching loops. Input
capacitor C1
must be placed close (< 5mm) to the IC
package. As little as 10mm of wire or PC trace from CIN to
VIN will cause problems such as inability to regulate or
oscillation.
The ground terminal of output capacitor C2 should tie
close to Pin 4 of the LT1949-1. Doing this reduces dI/dt in
the ground copper which keeps high frequency spikes to
a minimum. The DC/DC converter ground should tie to the
PC board ground plane at one place only, to avoid intro-
ducing dI/dt in the ground plane.
OPERATIO
U
19491i
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| LT1949-1EMS8#PBF | 功能描述:IC REG BOOST ADJ 1A 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| LT1949-1EMS8#TR | 功能描述:IC REG BOOST ADJ 1A 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| LT1949-1EMS8#TRPBF | 功能描述:IC REG BOOST ADJ 1A 8MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| LT1949-1EMS8TR | 功能描述:IC REG BOOST ADJ 1A 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開關(guān):52kHz 電流 - 輸出:1A 同步整流器:無 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12 |
| LT1949EMS8 | 功能描述:IC REG BOOST ADJ 1A 8MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:- 標(biāo)準包裝:2,500 系列:- 類型:升壓（升壓） 輸出類型:可調(diào)式 輸出數(shù):1 輸出電壓:1.24 V ~ 30 V 輸入電壓:1.5 V ~ 12 V PWM 型:電流模式，混合 頻率 - 開關(guān):600kHz 電流 - 輸出:500mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 包裝:帶卷 (TR) 供應(yīng)商設(shè)備封裝:8-SOIC |
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