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| 型号： | LT3972EMSE#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK ADJ 3.5A 10MSOP |
| 标准包装： | 50 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.79 V ~ 30 V |
| 输入电压： | 3.6 V ~ 33 V |
| PWM 型： | 电流模式，Burst Mode? |
| 频率 - 开关： | 230kHz ~ 2.45MHz |
| 电流 - 输出： | 3.5A |
| 同步整流器： | 无 |
| 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： | 管件 |
| 供应商设备封装： | 10-MSOP 裸露焊盘 |
| 产品目录页面： | 1332 (CN2011-ZH PDF) |
LT3972
APPLICATIONS INFORMATION
Frequency Compensation
The LT3972 uses current mode control to regulate the
output. This simpli?es loop compensation. In particular,
the LT3972 does not require the ESR of the output capacitor
for stability, so you are free to use ceramic capacitors to
achieve low output ripple and small circuit size. Frequency
compensation is provided by the components tied to the
V C pin, as shown in Figure 2. Generally a capacitor (C C )
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 cur-
rent is stepped from 1A to 3A and back to 1A.
LT3972
and a resistor (R C ) in series to ground are used. In addi-
tion, there may be lower value capacitor in parallel. This
capacitor (C F ) is not part of the loop compensation but
is used to ?lter noise at the switching frequency, and is
required only if a phase-lead capacitor is used or if the
output capacitor has high ESR.
CURRENT MODE
POWER STAGE
g m = 5.3mho
3M
SW
ERROR
AMPLIFIER
FB
g m =
500μmho
0.8V
R1
C PL
ESR
+
OUTPUT
C1
C1
Loop compensation determines the stability and transient
performance. Designing the compensation network is a bit
complicated and the best values depend on the application
and in particular the type of output capacitor. A practical
C F
V C
R C
GND
R2
POLYMER
OR
TANTALUM
CERAMIC
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
LT1375 data sheet contains a more thorough discussion of
loop compensation and describes how to test the stabil-
ity using a transient load. Figure 2 shows an equivalent
circuit for the LT3972 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 current proportional to
the voltage at the V C pin. Note that the output capacitor
C C
Figure 2. Model for Loop Response
V OUT
100mV/DIV
I L
1A/DIV
3972 F02
integrates this current, and that the capacitor on the V C pin
(C C ) integrates the error ampli?er output current, resulting
V IN = 12V
V OUT = 3.3V
10μs/DIV
3972 F03
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
Figure 3. Transient Load Response of the LT3972 Front Page
Application as the Load Current is Stepped from 1A to 3A.
V OUT = 5V
3972fa
13
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3972EMSE-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:33V, 3.5A, 2.4MHz Step-Down Switching Regulator with 75μA Quiescent Current |
| LT3972HMSE#PBF | 功能描述:IC REG BUCK ADJ 3.5A 10MSOP 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 |
| LT3972HMSE#TRPBF | 功能描述:IC REG BUCK ADJ 3.5A 10MSOP 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 |
| LT3972IDD#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:- 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 |
| LT3972IDD#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 |
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