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参数资料
| 型号： | LT3844IFE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 10/24页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST INV PWM 16TSSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 330kHz |
| 占空比： | 95% |
| 电源电压： | 4 V ~ 60 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 无 |
| 反相： | 是 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 包装： | 带卷 (TR) |
LT3844
OPERATION
(Refer to Functional Diagram)
the C SS pin voltage then the current threshold set by the
DC control voltage, V C , is decreased and the inductor cur-
rent is lowered. This in turn decreases the output voltage
slew rate allowing the C SS pin voltage ramp to catch up
to the V FB pin voltage. An internal 100mV offset is added
to the V FB pin voltage relative to the to C SS pin voltage
so that at start-up the soft-start circuit will discharge the
V C pin voltage below the DC control voltage equivalent to
zero inductor current. This will reduce the input supply
inrush current. The soft-start circuit is disabled once the
C SS pin voltage has been charged to 200mV above the
internal reference of 1.231V.
During a V IN UVLO, V CC UVLO or SHDN UVLO event, the
C SS pin voltage is discharged with a 50μA current source.
In normal operation the C SS pin voltage is clamped to a
diode above the V FB pin voltage. Therefore, the value of
the C SS capacitor is relevant in how long of a fault event
will retrigger a soft-start. In other words, if any of the
above UVLO conditions occur, the C SS pin voltage will be
discharged with a 50μA current source. There is a diode
worth of voltage headroom to ride through the fault before
the C SS pin voltage enters its active region and the soft-
start function is enabled.
Also, since the C SS pin voltage is clamped to a diode above
the V FB pin voltage, during a short circuit the C SS pin volt-
age is pulled low because the V FB pin voltage is low. Once
the short has been removed the V FB pin voltage starts to
recover. The soft-start circuit takes control of the output
voltage slew rate once the V FB pin voltage has exceeded
the slowly ramping C SS pin voltage, reducing the output
voltage overshoot during a short-circuit recovery.
APPLICATIONS INFORMATION
The basic LT3844 step-down (buck) application, shown
in the Typical Application on the front page, converts a
larger positive input voltage to a lower positive or negative
output voltage. This Application Information section assists
selection of external components for the requirements of
the power supply.
Slope/Antislope Compensation
The IC incorporates slope compensation to eliminate
potential subharmonic oscillations in the current control
loop. The IC’s slope compensation circuit imposes an
arti?cial ramp on the sensed current to increase the rising
slope as duty cycle increases.
Typically, this additional ramp affects the sensed current
value, thereby reducing the achievable current limit value
by the same amount as the added ramp represents. As
such, the current limit is typically reduced as the duty cycle
increases. The LT3844, however, contains antislope com-
pensation circuitry to eliminate the current limit reduction
associated with slope compensation. As the slope compen-
sation ramp is added to the sensed current, a similar ramp
is added to the current limit threshold. The end result is that
the current limit is not compromised so the LT3844 can
provide full power regardless of required duty cycle.
Shutdown
The LT3844 includes a shutdown mode where all the
internal IC functions are disabled and the V IN current is
reduced to less than 10μA. The shutdown pin can be used
for undervoltage lockout with hysteresis, micropower shut-
down or as a general purpose on/off control of the converter
output. The shutdown function has two thresholds. The
?rst threshold, a precision 1.23V threshold with 120mV
of hysteresis, disables the converter from switching. The
second threshold, approximately a 0.7V referenced to
SGND, completely disables all internal circuitry and reduces
the V IN current to less than 10μA. See the Application
Information section for more information.
R SENSE Selection
The current sense resistor, RS ENSE , monitors the inductor
current of the supply (See Typical Application on front
page). Its value is chosen based on the maximum required
output load current. The LT3844 current sense ampli?er
has a maximum voltage threshold of, typically, 100mV.
3844fb
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3845 | 制造商:Cooper Crouse-Hinds 功能描述: |
| LT3845_1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency |
| LT3845A | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage, Current Mode Switching Regulator Controller Thermal Shutdown |
| LT3845AEFE#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LT3845AEFE#PBF | 制造商:Linear Technology 功能描述:IC DC-DC CONV 500kHz TSSOP16 制造商:Linear Technology 功能描述:IC, DC-DC CONV, 500kHz, TSSOP16 |
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