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参数资料
| 型号： | LT1912EMSE#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 4.2 A SWITCHING REGULATOR, 240 kHz SWITCHING FREQ-MAX, PDSO10 |
| 封装： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件页数： | 5/24页 |
| 文件大小： | 365K |
| 代理商： | LT1912EMSE#PBF |
LT1912
13
1912fa
APPLICATIONS INFORMATION
and in particular the type of output capacitor. A practical
approach is to start with one of the circuits in this data
sheet that is similar to your application and tune the com-
pensation network to optimize the performance. Stability
should then be checked across all operating conditions,
including load current, input voltage and temperature. The
LT1375datasheetcontainsamorethoroughdiscussionof
loop compensation and describes how to test the stabil-
ity using a transient load. Figure 2 shows an equivalent
circuit for the LT1912 control loop. The error amplifier is a
transconductance amplifier with finite output impedance.
The power section, consisting of the modulator, power
switch and inductor, is modeled as a transconductance
amplifier generating an output current proportional to
the voltage at the VC pin. Note that the output capacitor
integrates this current, and that the capacitor on the VC pin
(CC)integratestheerroramplifieroutputcurrent,resulting
in two poles in the loop. In most cases a zero is required
and comes from either the output capacitor ESR or from
a resistor RC in series with CC. This simple model works
well as long as the value of the inductor is not too high
and the loop crossover frequency is much lower than the
switching frequency. A phase lead capacitor (CPL) across
the feedback divider may improve the transient response.
Figure3showsthetransientresponsewhentheloadcurrent
is stepped from 500mA to 1500mA and back to 500mA.
BOOST and BIAS Pin Considerations
Capacitor C3 and the internal boost Schottky diode (see
the Block Diagram) are used to generate a boost volt-
age that is higher than the input voltage. In most cases
a 0.22F capacitor will work well. Figure 2 shows three
ways to arrange the boost circuit. The BOOST pin must be
more than 2.3V above the SW pin for best efficiency. For
outputs of 3V and above, the standard circuit (Figure 4a)
is best. For outputs between 2.8V and 3V, use a 1F boost
capacitor. A 2.5V output presents a special case because it
is marginally adequate to support the boosted drive stage
whileusingtheinternalboostdiode.ForreliableBOOSTpin
operation with 2.5V outputs use a good external Schottky
diode (such as the ON Semi MBR0540), and a 1F boost
capacitor (see Figure 4b). For lower output voltages the
boost diode can be tied to the input (Figure 4c), or to
another supply greater than 2.8V. Tying BD to VIN reduces
the maximum input voltage to 30V. The circuit in Figure 4a
is more efficient because the BOOST pin current and BD
pin quiescent current comes from a lower voltage source.
You must also be sure that the maximum voltage ratings
of the BOOST and BD pins are not exceeded.
The minimum operating voltage of an LT1912 application
is limited by the minimum input voltage (3.6V) and by the
maximum duty cycle as outlined in a previous section. For
proper startup, the minimum input voltage is also limited
by the boost circuit. If the input voltage is ramped slowly,
thentheboostcapacitormaynotbefullycharged.Because
–
+
0.8V
SW
VC
gm =
420mho
GND
3Meg
LT1912
1912 F02
R1
OUTPUT
ESR
CF
CC
RC
ERROR
AMPLIFIER
FB
R2
C1
CURRENT MODE
POWER STAGE
gm = 3.5mho
+
POLYMER
OR
TANTALUM
CERAMIC
CPL
Figure 2. Model for Loop Response
Figure 3. Transient Load Response of the LT1912 Front Page
Application as the Load Current is Stepped from 500mA to
1500mA. VOUT = 3.3V
1912 F03
IL
0.5A/DIV
VOUT
100mV/DIV
10s/DIV
VIN = 12V; FRONT PAGE APPLICATION
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT1912EMSE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 500kHz Step-Down Switching Regulator |
| LT1913 | 制造商:LINER 制造商全称: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 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
| LT1913EDD#TRPBF | 功能描述:IC REG BUCK ADJ 3.5A 10DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 设计资源:Design Support Tool 标准包装:1 系列:- 类型:升压（升压） 输出类型:固定 输出数:1 输出电压:3V 输入电压:0.75 V ~ 2 V PWM 型:- 频率 - 开关:- 电流 - 输出:100mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SOT-23-5 细型，TSOT-23-5 包装:剪切带 (CT) 供应商设备封装:TSOT-23-5 其它名称:AS1323-BTTT-30CT |
| LT1913EDD-PBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:25V, 3.5A, 2.4MHz Step-Down Switching Regulator |
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