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| 型号： | LT3684EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 14/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 2A 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 1.27 V ~ 20 V |
| 输入电压： | 3.6 V ~ 34 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 300kHz ~ 3MHz |
| 电流 - 输出： | 2A |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LT3684
APPLICATIONS INFORMATION
LT3684
V OUT = 12V, FRONT PAGE APPLICATION
CURRENT MODE
POWER STAGE
SW
OUTPUT
g m = 3.5mho
ERROR
AMPLIFIER
R1
C PL
I L
1A/DIV
FB
3M
g m =
330 μ mho
1.265V
ESR
+
C1
V OUT
C1
POLYMER
CERAMIC
100mV/DIV
V C
GND
OR
TANTALUM
10 μ s/DIV
3684 F03
C F
R C
C C
R2
Figure 3. Transient Load Response of the LT3684 Front Page
Application as the Load Current is Stepped from 500mA to
1500mA. V OUT = 3.3V
3684 F02
Figure 2. Model for Loop Response
Loop compensation determines the stability and transient
performance. Designing the compensation network is a
bit complicated and the best values depend on the ap-
plication 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 compensation network to optimize the performance.
Stability should then be checked across all operating
conditions, including load current, input voltage and
temperature. The LT1375 data sheet contains a more
thorough discussion of loop compensation and describes
how to test the stability using a transient load. Figure 2
shows an equivalent circuit for the LT3684 control loop.
The error ampli?er is a transconductance ampli?er with
?nite output impedance. The power section, consisting of
the modulator, power switch and inductor, is modeled as
a transconductance ampli?er generating an output cur-
rent proportional to the voltage at the V C pin. Note that
the output capacitor integrates this current, and that the
capacitor on the V C pin (C C ) integrates the error ampli-
?er output current, 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 R C in series with
C C . 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 (C PL ) across the feedback divider
may improve the transient response. Figure 3 shows the
transient response when the load current 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 0.22μF 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 ef?ciency. For
outputs of 3V and above, the standard circuit (Figure 4a)
is best. For outputs between 2.8V and 3V, use a 1μF boost
capacitor. A 2.5V output presents a special case because it
is marginally adequate to support the boosted drive stage
while using the internal boost diode. For reliable BOOST pin
operation with 2.5V outputs use a good external Schottky
diode (such as the ON Semi MBR0540), and a 1μF 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. The circuit in Figure 4a
is more ef?cient because the BOOST pin current and BIAS
pin quiescent current comes from a lower voltage source.
You must also be sure that the maximum voltage ratings
of the BOOST and BIAS pins are not exceeded.
The minimum operating voltage of an LT3684 application
is limited by the minimum input voltage (3.6V) and by the
maximum duty cycle as outlined in a previous section. For
3684f
14
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相关代理商/技术参数 |
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| LT3684EMSE | 制造商:LINER 制造商全称:Linear Technology 功能描述:36V, 2A, 2.8MHz Step-Down Switching Regulator |
| LT3684EMSE#PBF | 功能描述:IC REG BUCK ADJ 2A 10MSOP 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 |
| LT3684EMSE#PBF | 制造商:Linear Technology 功能描述:Switching Regulator IC 制造商:Linear Technology 功能描述:IC, STEP-DOWN REGULATOR, MSOP-10 |
| LT3684EMSE#TRPBF | 功能描述:IC REG BUCK ADJ 2A 10MSOP 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:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LT3684EMSEPBF | 制造商:Linear Technology 功能描述:36V/2A Buck(non BurstMode LT3481) LT3684 |
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