- 您现在的位置：买卖IC网 > PDF目录1832 > LTC3852EUDD#PBF (Linear Technology)IC REG CTRLR DOUBLER PWM 24-QFN PDF资料下载
参数资料
| 型号： | LTC3852EUDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 13/32页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR DOUBLER PWM 24-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 810kHz |
| 占空比： | 99% |
| 电源电压： | 2.7 V ~ 38 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 是 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页当前第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页
LTC3852
OPERATION
is recommended that there is always a load present during
the drop-out transition to ensure C B is recharged.
Shutdown and Start-Up (RUN, SHDN and TRACK/SS)
The switching regulator section of the LTC3852 can be
shut down using the RUN pin. Pulling this pin below 1.1V
disables the controller and most of the internal circuitry.
Releasing the RUN pin allows an internal 2μA current to
pull up the pin and enable the controller. Alternatively, the
RUN pin may be externally pulled up or driven directly by
logic. Be careful not to exceed the absolute maximum
rating of 6V on this pin.
The start-up of the controller’s output voltage, V OUT , is
controlled by the voltage on the TRACK/SS pin. When the
voltage on the TRACK/SS pin is less than the 0.8V internal
reference, the LTC3852 regulates the V FB voltage to the
TRACK/SS pin voltage instead of the 0.8V reference. This
allows the TRACK/SS pin to be used to program a soft-start
by connecting an external capacitor from the TRACK/SS
pin to GND. An internal 1μA pull-up current charges this
capacitor, creating a voltage ramp on the TRACK/SS pin.
As the TRACK/SS voltage rises linearly from 0V to 0.8V
(and beyond), the output voltage V OUT rises smoothly from
zero to its ?nal value. Alternatively, the TRACK/SS pin can
be used to cause the start-up of V OUT to “track” another
supply. Typically, this requires connecting to the TRACK/SS
pin an external resistor divider from the other supply to
ground (see the Applications Information section). When
the RUN pin is pulled low to disable the controller, or when
INTV CC drops below its undervoltage lockout threshold
of 3.2V, the TRACK/SS pin is pulled low by an internal
MOSFET. When in undervoltage lockout, the controller is
disabled and the external MOSFETs are held off.
The charge pump is separately controlled by SHDN . In
shutdown mode, all charge pump circuitry is turned off and it
draws only leakage current from the V IN1 supply. Furthermore,
V PUMP is disconnected from V IN1 . The SHDN pin is a CMOS
input with a threshold voltage of approximately 0.7V. The
charge pump is in shutdown when a logic low is applied to
the SHDN pin. Since the SHDN pin is a very high impedance
CMOS input, it should never be allowed to ?oat. To ensure
that its state is de?ned, it must always be driven with a valid
logic level not exceeding V IN1 , even if it is tied to RUN.
Since the output voltage of the charge pump can go above
the input voltage, special circuitry is required to control the
internal logic. Detection logic will draw an input current
of 5μA when in shutdown. However, this current will
be eliminated if the output voltage (V PUMP ) is less than
approximately 0.8V.
The charge pump has built-in soft-start circuitry to prevent
excessive current ?ow during start-up. The soft-start is
achieved by charging an internal capacitor with a very weak
current source. The voltage on this capacitor, in turn, slowly
ramps the amount of current available to the output storage
capacitor from zero to a value of 50mA over a period of
approximately 125μs. The soft-start circuit is reset in the
event of a commanded shutdown or thermal shutdown.
Light Load Current Operation (Burst Mode Operation,
Pulse skipping or Continuous Conduction)
The LTC3852 can be enabled for high ef?ciency Burst
Mode operation, constant frequency pulse skipping mode
or forced continuous conduction mode. To select forced
continuous operation, tie the MODE/PLLIN pin to INTV CC .
To select pulse skipping mode of operation, ?oat the
MODE/PLLIN pin or tie it to GND2. To select Burst Mode
operation, tie MODE/PLLIN to INTV CC through a resistor
no less than 50k, but no greater than 250k.
When the controller is enabled for Burst Mode operation,
the peak current in the inductor is set to approximately
one-fourth of the maximum sense voltage even though
the voltage on the I TH pin indicates a lower value. If the
average inductor current is higher than the load current,
the error ampli?er, EA, will decrease the voltage on the I TH
pin. When the I TH voltage drops below 0.4V, the internal
sleep signal goes high (enabling sleep mode) and both
external MOSFETs are turned off.
In sleep mode, the load current is supplied by the output
capacitor. As the output voltage decreases, the EA’s output
begins to rise. When the output voltage drops enough, the
sleep signal goes low, and the controller resumes normal
operation by turning on the top external MOSFET on the
next cycle of the internal oscillator. When the controller is
enabled for Burst Mode operation, the inductor current is
not allowed to reverse. The reverse current comparator,
I REV , turns off the bottom external MOSFET just before the
3852f
13
相关PDF资料 |
PDF描述 |
|---|---|
| LTC3853EUJ#PBF | IC REG CTRLR BUCK PWM CM 40-QFN |
| LTC3854EMSE#PBF | IC REG CTRLR BUCK PWM CM 12-MSOP |
| LTC3855IUJ#PBF | IC REG CTRLR BUCK PWM CM 40-QFN |
| LTC3856IFE#TRPBF | IC REG CTRLR BUCK PWM CM 38TSSOP |
| LTC3858IUH#TRPBF | IC REG CTRLR BUCK PWM CM 32-QFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3852IUDD#PBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3852IUDD#TRPBF | 功能描述:IC REG CTRLR DOUBLER PWM 24-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 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:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3853EUJ#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJ#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 40-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC3853EUJPBF | 制造商:Linear Technology 功能描述:DC-DC Controller Triple Buck 24V QFN40 |
发布紧急采购，3分钟左右您将得到回复。