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参数资料
| 型号： | LTC3553EUD#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC20 |
| 封装： | 3 X 3 MM, 0.75 MM HEIGHT, LEAD FREE, PLASTIC, QFN-20 |
| 文件页数： | 13/36页 |
| 文件大小： | 518K |
| 代理商： | LTC3553EUD#TRPBF |
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LTC3553
20
3553fa
OPERATION
BUCK REGULATOR
Introduction
The LTC3553 includes a constant-frequency current-
mode 200mA buck regulator. At light loads, the regulator
automatically enters Burst Mode operation to maintain
high efciency.
Applications with a near-zero-current sleep or memory
keep-alive mode can command the LTC3553 buck regula-
tor into a standby mode that maintains output regulation
while drawing only 1.5μA quiescent current. Load capability
drops to 10mA in this mode.
The buck regulator is enabled, disabled and sequenced
through the pushbutton interface (see the Pushbutton
Interface section for more information). It is recommended
that the buck regulator input supply (BVIN) be connected
to the system supply pin (VOUT). This is recommended
because the undervoltage lockout circuit on the VOUT pin
(VOUT UVLO) disables the buck regulator when the VOUT
voltage drops below the VOUT UVLO threshold. If driv-
ing the buck regulator input supply from a voltage other
than VOUT, the regulator should not be operated outside
its specied operating voltage range as operation is not
guaranteed beyond this range.
Output Voltage Programming
Figure 3 shows the buck regulator application circuit. The
output voltage for the buck regulator is programmed using
a resistor divider from the buck regulator output connected
to the feedback pin (BUCK_FB) such that:
V
BUCK = 0.8V
R1
R2
+1
Typical values for R1 can be as high as 2.2MΩ.
(R1 + R2) can be as high as 3MΩ. The capacitor CFB
cancels the pole created by feedback resistors and the
input capacitance of the BUCK_FB pin and also helps
to improve transient response for output voltages much
greater than 0.8V. A variety of capacitor sizes can be used
for CFB but a value of 10pF is recommended for most
applications. Experimentation with capacitor sizes between
2pF and 22pF may yield improved transient response.
Normal Buck Operating Mode (STBY Pin Low)
In normal mode (STBY pin low), the buck regulator per-
forms as a traditional constant-frequency current mode
switching regulator. Switching frequency is determined
by an internal oscillator which operates at 1.125MHz. An
internal latch is set at the start of every oscillator cycle,
turning on the main P-channel MOSFET switch. During
each cycle, a current comparator compares the inductor
current to the output of an error amplier. The output of
the current comparator resets the internal latch, which
causes the main P-channel MOSFET switch to turn off and
the N-channel MOSFET synchronous rectier to turn on.
The N-channel MOSFET synchronous rectier turns off
at the end of the clock cycle, or when the current through
the N-channel MOSFET synchronous rectier drops to
zero, whichever happens rst. Via this mechanism, the
error amplier adjusts the peak inductor current to deliver
the required output power. All necessary compensation
is internal to the buck regulator requiring only a single
ceramic output capacitor for stability.
At light load and no-load conditions, the buck automatically
switches to a power-saving hysteretic control algorithm
that operates the switches intermittently to minimize
switching losses. Known as Burst Mode operation, the
Figure 3. Buck Regulator Application Circuit
3553 F03
0.8V
VIN
CFB
COUT
VBUCK
MP
MN
GND
BUCK_FB
R1
SW
L
PWM
CONTROL
EN
STBY
R2
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相关代理商/技术参数 |
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| LTC3554 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower USB Power Manager with Li-Ion Charger and Two Step-Down Regulators |
| LTC3554EPD | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower USB Power Manager with Li-Ion Charger and Two Step-Down Regulators |
| LTC3554EPD#PBF | 功能描述:IC USB POWER MANAGER 20-UTQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 标准包装:1 系列:- 应用:手持/移动设备 电流 - 电源:- 电源电压:3 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-WFDFN 裸露焊盘 供应商设备封装:14-LLP-EP（4x4） 包装:Digi-Reel® 配用:LP3905SD-30EV-ND - BOARD EVALUATION LP3905SD-30 其它名称:LP3905SD-30DKR |
| LTC3554EPD#TRPBF | 功能描述:IC USB POWER MANAGER 20-UTQFN RoHS:是 类别:集成电路 (IC) >> PMIC - 电源管理 - 专用 系列:- 应用说明:Ultrasound Imaging Systems Application Note 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:37 系列:- 应用:医疗用超声波成像，声纳 电流 - 电源:- 电源电压:2.37 V ~ 6 V 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:56-WFQFN 裸露焊盘 供应商设备封装:56-TQFN-EP（8x8） 包装:管件 |
| LTC3554EPDPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Micropower USB Power Manager with Li-Ion Charger and Two Step-Down Regulators |
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