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參數(shù)資料
| 型號： | LT3695EMSE-5#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 2 A SWITCHING REGULATOR, 2420 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-16 |
| 文件頁數(shù)： | 9/30頁 |
| 文件大?。?/td> | 491K |
| 代理商： | LT3695EMSE-5#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
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LT3695EMSEPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:1A Fault Tolerant Micropower Step-Down Regulator |
| LT3695EMSETRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:1A Fault Tolerant Micropower Step-Down Regulator |
| LT3695HMSE#PBF | 功能描述:IC REG BUCK ADJ 1A 16MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 設計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應商設備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT3695HMSE#TRPBF | 功能描述:IC REG BUCK ADJ 1A 16MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 設計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應商設備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
| LT3695HMSE-3.3#PBF | 功能描述:IC REG BUCK 3.3V 1A 16MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關穩(wěn)壓器 系列:- 設計資源:Design Support Tool 標準包裝:1 系列:- 類型:升壓（升壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3V 輸入電壓:0.75 V ~ 2 V PWM 型:- 頻率 - 開關:- 電流 - 輸出:100mA 同步整流器:是 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-5 細型，TSOT-23-5 包裝:剪切帶 (CT) 供應商設備封裝:TSOT-23-5 其它名稱:AS1323-BTTT-30CT |
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