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| 型号： | LT3695EMSE-3.3#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 2 A SWITCHING REGULATOR, 2420 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件页数： | 9/30页 |
| 文件大小： | 491K |
| 代理商： | LT3695EMSE-3.3#TRPBF |
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LT3695 Series
17
3695fa
Audible Noise
Ceramic capacitors are small, robust and have very low
ESR. However, ceramic capacitors can sometimes cause
problems when used with the LT3695 regulators due to
their piezoelectric nature. When in Burst Mode operation,
the LT3695 regulators’ switching frequency depends on the
load current, and at very light loads the LT3695 regulators
can excite the ceramic capacitor at audio frequencies, gen-
erating audible noise. Since the LT3695 regulators operate
at a lower current limit during Burst Mode operation, the
noise is typically very quiet. If this is unacceptable, use
a high performance tantalum or electrolytic capacitor at
the output.
Frequency Compensation
The LT3695 regulators use current mode control to
regulate the output. This simplies loop compensation.
In particular, the LT3695 regulators do 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 VC pin, as shown in Figure 1.
Generally a capacitor (CC) and a resistor (RC) in series to
ground are used. In addition, there may be a lower value
capacitor in parallel. This capacitor (CF) is used to lter
noise at the switching frequency, and is required only if a
phase-lead capacitor (CPL, LT3695 only) is used or if the
output capacitor has high ESR.
APPLICATIONS INFORMATION
Loop compensation determines the stability and transient
performance. Optimizing the design of the compensation
network depends on the application and type of output
capacitor. A practical approach is to start with one of the
circuits in this data sheet that is similar to your applica-
tion 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 1
shows an equivalent circuit for the LT3695 regulators
control loop. The error amplier is a transconductance
amplier with nite output impedance. The power section,
consisting of the modulator, power switch and inductor, is
modeled as a transconductance amplier 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) integrates the error
amplier 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 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, LT3695 only) across the feedback divider
may improve the transient response. Figure 2 shows the
transient response when the load current is stepped from
300mA to 650mA and back to 300mA.
0.8V
LT3695
CF
RC
VC
3M
3695 F01
CURRENT MODE
POWER STAGE
gm = 1.25S
CC
CPL
C1
R2
R1
SW
FB
GND
OUTPUT
CERAMIC
POLYMER
OR
TANTALUM
OR
ELECTROLITIC
ESR
+
C1
–
+
gm = 430μS
Figure 1. Model for Loop Response. Note That R1 and R2 Are
Integrated in the LT3695-3.3 and LT3695-5
Figure 2. Transient Load Response of the LT3695
Regulators. A 3.3VOUT Typical Application with VIN = 12V
as the Load Current Is Stepped from 300mA to 650mA
VOUT
100mV/DIV
ILOAD
0.5A/DIV
20μs/DIV
3695 F02
相关PDF资料 |
PDF描述 |
|---|---|
| LT3751IUFD#TR | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| LT3751IUFD#TRPBF | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| LT3751EFE | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO20 |
| LT3751EUFD#TRPBF | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| LT3751EUFD | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3695EMSE-5#PBF | 功能描述:IC REG BUCK 5V 1A 16MSOP 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 |
| LT3695EMSE-5#PBF | 制造商:Linear Technology 功能描述:IC STEP-DOWN REGULATOR MSOP-16 |
| LT3695EMSE-5#TRPBF | 功能描述:IC REG BUCK 5V 1A 16MSOP 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 |
| LT3695EMSEPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:1A Fault Tolerant Micropower Step-Down Regulator |
| LT3695EMSETRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:1A Fault Tolerant Micropower Step-Down Regulator |
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