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| 型号： | LTC3447EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 7/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 0.6A 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： | 0.69 V ~ 2.05 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1MHz |
| 电流 - 输出： | 600mA |
| 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： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LTC3447
OPERATIO
BUCK OPERATION
50mA. When below this level, the power MOSFETs and any
unneeded circuitry are turned off, reducing the quiescent
V FB
EA
PEAK CURRENT LEVEL REF
V IN
current to 33μA, and the peak current level reference level
is held at 150mA. The LTC3447 remains in this sleep state
V REF
until the output voltage falls below the output voltage set-
ting. Once this occurs, the regulator wakes up and allows
RS
LATCH
I COMP
RS
the inductor to develop 150mA current pulses. For light
OSC
S
Q
loads, this will cause the output voltage to increase and the
R
QB
BURST
LOGIC
I RCMP
PFET
NFET
SW
internal peak current reference to decrease. When the peak
current reference falls to below 50mA, the part re-enters
sleep mode and the cycle is repeated. This process repeats
at a rate that is dependent on the load demand.
Pulse Skipping Mode Operation
At light loads, the inductor current may reach zero or
BUCK REGULATOR
Figure 3. LTC3447 Buck Regulator Diagram
3447 AI01
reverse on each pulse. The bottom MOSFET is turned off
by the current reversal comparator, I RCMP , and the switch
voltage will ring. This is discontinuous mode operation,
Main Control Loop
The LTC3447 uses current mode step-down architecture
with both the main (P-channel MOSFET) and synchronous
(N-channel MOSFET) switches internal. During normal
operation, the internal top power MOSFET is turned on
each cycle when the oscillator sets the RS latch, and
turned off when the current comparator, I COMP , resets
the RS latch. The peak inductor current at which I COMP
resets the RS latch, is controlled by the output of error
ampli?er EA. When the load current increases, it causes
a slight decrease in the feedback voltage, FB, relative to
an internal reference voltage, which in turn, causes the
EA ampli?er’s output voltage to increase until the average
inductor current matches the new load current. While the
top MOSFET is off, the bottom MOSFET is turned on until
either the inductor current starts to reverse, as indicated
by the current reversal comparator I RCMP , or the beginning
of the next clock cycle.
Burst Mode Operation
The LTC3447 is capable of Burst Mode operation in which
the internal power MOSFETs operate intermittently based
on load demand. Burst Mode operation can be disabled via
the I 2 C interface. When Burst Mode operation is disabled,
the regulator is in pulse skipping mode operation.
During Burst Mode operation, the LTC3447’s internal
circuits sense when the inductor peak current falls below
and is normal behavior for a switching regulator. At very
light loads, the LTC3447 will automatically skip pulses
in pulse skipping mode operation to maintain output
regulation. This feature is enabled when the Burst Mode
operation is disabled.
Short-Circuit Protection
When the output is shorted to ground, the frequency of
the oscillator is reduced to about 160kHz. This frequency
foldback ensures that the inductor current has more
time to decay, thereby preventing thermal runaway. The
oscillator’s frequency will progressively increase to 1MHz
when V OUT rises above 0V.
Dropout Operation
When using the optional external feedback resistors, it is
possible for V IN to approach the output voltage level. As
the input supply voltage decreases to a value approaching
the output voltage, the duty cycle increases toward the
maximum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one cycle
until it reaches 100% duty cycle. The output voltage will
then be determined by the input voltage minus the voltage
drop across the P-channel MOSFET and the inductor.
An important detail to remember is that at low input supply
voltages, the R DS(ON) of the P-channel switch increases
(see Typical Performance Characteristics). Therefore,
3447f
7
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相关代理商/技术参数 |
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|---|---|
| LTC3448 | 制造商:LINER 制造商全称:Linear Technology 功能描述:1.5MHz/2.25MHz, 600mA Synchronous Step-Down Regulator with LDO Mode |
| LTC3448EDD | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8DFN RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:MIC23xxx HyperLight Load™ Regulators 标准包装:5,000 系列:HyperLight Load® 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.8V 输入电压:2.7 V ~ 5.5 V PWM 型:混合物 频率 - 开关:4MHz 电流 - 输出:2A 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:8-VFDFN 裸露焊盘，8-MLF? 包装:带卷 (TR) 供应商设备封装:8-MLF?（2x2） 产品目录页面:1094 (CN2011-ZH PDF) 其它名称:576-3303-2 |
| LTC3448EDD#PBF | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8DFN 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 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:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC3448EDD#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8DFN 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 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:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
| LTC3448EMS8E | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:否 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:升压（升压） 输出类型:可调式 输出数:1 输出电压:1.24 V ~ 30 V 输入电压:1.5 V ~ 12 V PWM 型:电流模式，混合 频率 - 开关:600kHz 电流 - 输出:500mA 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:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:8-SOIC |
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