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| 型号： | LTC3852EUDD#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/32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 |
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LTC3852
OPERATION
Main Control Loop
The LTC3852 is a constant frequency, current mode
step-down DC/DC controller which can be powered by
an onboard charge pump. Supplies as low as 2.7V, when
doubled by the charge pump, provide 5V to the LTC3852’s
control logic and gate drives, supporting a wide selection
of logic-level MOSFETs.
The alternative arrangement in Figure 1b allows the
LTC3852 to step down from as high as 38V, while powering
itself from an available 3.3V bus. The input to the charge
pump, V IN1 , is connected to 3.3V instead of the drain of
the top MOSFET. It is not necessary to step the high input
voltage down to 5V through a linear regulator. Logic level
MOSFETs are usable in both cases.
During normal operation, the controller’s top MOSFET is
turned on when the clock sets the RS latch, and is turned
V IN
3.3V
off when the main current comparator, I CMP , resets the
RS latch. The peak inductor current at which I CMP resets
the RS latch is controlled by the voltage on the I TH pin,
which is the output of the error ampli?er EA. The V FB pin
V PUMP
V IN1
TG
BG
receives the voltage feedback signal, which is compared
to the internal reference voltage by the EA. When the
load current increases, it causes a slight decrease in V FB
relative to the 0.8V reference, which in turn causes the
I TH voltage to increase until the average inductor current
matches the new load current. After the top MOSFET has
V IN2
INTV CC
3852 F01a
Figure 1a
turned off, the bottom MOSFET is turned on until either
the inductor current starts to reverse, as indicated by the
reverse current comparator, I REV , or the beginning of the
next cycle.
3.3V
V IN1
TG
V IN ≤ 38V
The charge pump section uses a switched capacitor doubler
to boost V IN1 to 2 ￥ V IN1 , with a regulated maximum of
5V. Regulation is achieved by sensing the output voltage
V PUMP
V IN2
BG
through an internal resistor divider and modulating the
charge pump output current based on the error signal. A
2-phase nonoverlapping clock activates the charge pump
switches. The ?ying capacitor is charged from V IN1 on
the ?rst phase of the clock. On the second phase of the
clock it is stacked in series with V IN1 and connected to
V PUMP . This sequence of charging and discharging the
?ying capacitor continues at a free running frequency of
1.2MHz (typ).
Two con?gurations address most LTC3852 applications.
Figure 1a covers the single low input voltage case, typically
3.3V. The input to the charge pump, V IN1 , is connected to
the same input voltage as the drain of the top MOSFET.
V PUMP , V IN2 and INTV CC are tied together, so that the
charge pump’s 5V output provides all power to the buck
controller section.
INTV CC
3852 F01b
Figure 1b
INTV CC Power
Power for the top and bottom MOSFET drivers and most
other internal circuitry is derived from the INTV CC pin. Peak
current drawn from INTV CC should not exceed 50mA.
The top MOSFET driver is biased from the ?oating boot-
strap capacitor, C B , which normally recharges during each
off cycle through an external diode when the top MOSFET
turns off. If V IN decreases to a voltage close to V OUT , the
loop may enter dropout and attempt to turn on the top
MOSFET continuously. The dropout detector detects this
and forces the top MOSFET off for about 1/10 of the clock
period every tenth cycle to allow C B to recharge. However, it
3852f
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相关代理商/技术参数 |
参数描述 |
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| 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 |
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