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参数资料
| 型号： | LTC3785EUF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 3 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC24 |
| 封装： | 4 X 4 MM, PLASTIC, MO-220WGGD, QFN-24 |
| 文件页数： | 19/20页 |
| 文件大小： | 275K |
| 代理商： | LTC3785EUF |
LTC3785
3785fc
operaTion
MAIN CONTROL LOOP
The LTC3785 is a buck-boost voltage mode controller that
provides an output voltage above, equal to or below the
input voltage.
The LTC proprietary topology and control architecture also
employs drain-to-source sensing (No RSENSE)forforward
and reverse current limiting. The controller provides
all N-channel MOSFET output switch drive, facilitating
single package multiple power switch technology along
with lower RDS(ON). The error amp output voltage (VC)
determines the output duty cycle of the switches. Since
the VC pin is a filtered signal, it provides rejection of high
frequency noise.
The FB pin receives the voltage feedback signal, which
is compared to the internal reference voltage by the er-
ror amplifier. The top MOSFET drivers are biased from a
floating bootstrap capacitor, which is normally recharged
during each off cycle through an external diode when the
top MOSFET turns off. Optional Schottky diodes can be
connected across synchronous switch B and D to provide
a lower drop during the dead time and eliminate efficiency
loss due to body diode reverse recovery.
The main control loop is shut down by pulling the RUN/
SS pin low. An internal 1A current source charges the
RUN/SS pin and when the pin voltage is higher than 0.7V
the IC is enabled. The VC voltage is then clamped to the
RUN/SS voltage minus 0.7V while CSS is slowly charged
during start-up. This soft-start clamping prevents inrush
current draw from the input power supply.
POWER SWITCH CONTROL
Figure 1 shows a simplified diagram of how the four power
switchesareconnectedtotheinductor,VIN,VOUTandGND.
Figure 2 shows the regions of operation for the LTC3785
as a function of duty cycle D. The power switches are
properly controlled so that the transfer between modes
is continuous.
Buck Region (VIN > VOUT)
Switch D is always on and switch C is always off during
buck mode. When the error amp output voltage, VC, is ap-
proximately above 0.1V, output A begins to switch. During
the off time of switch A, synchronous switch B turns on for
theremainderoftheswitchingperiod.SwitchesAandBwill
alternate similar to a typical synchronous buck regulator.
As the control voltage increases, the duty cycle of switch
A increases until the max duty cycle of the converter in
buck mode reaches DMAX_BUCK, given by:
DMAX_BUCK = 100 – D4(SW)%
where D4(SW) = duty cycle % of the four switch range.
D4(SW) = (300ns f) 100%
where f = operating frequency, Hz.
Beyond this point the four switch or buck-boost region
is reached.
Buck-Boost or Four Switch (VIN ~ VOUT)
When the error amp output voltage, VC, is above ap-
proximately 0.65V, switch pair AD remain on for duty
cycle DMAX_BUCK, and the switch pair AC begin to phase
in. As switch pair AC phases in, switch pair BD phases
out accordingly. When the VC voltage reaches the edge of
Figure 1. Output Switch Configuration
Figure 2. Operation Mode vs VC Voltage
SW2
BG1
C
3785 F01
SW1
B
BG2
L
VOUT
VIN
TG1
D
A
TG2
BOOST REGION
BUCK/BOOST REGION
FOUR SWITCH PWM
90%
DMAX
BOOST
DMIN
BOOST
A ON, B OFF
PWM C, D SWITCHES
BUCK REGION
DMIN
BUCK
3785 F02
DMAX
BUCK
D ON, C OFF
PWM A, B SWITCHES
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3785EUF#PBF | 功能描述:IC REG CTRLR BST PWM VM 24-QFN 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 |
| LTC3785EUF#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 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) |
| LTC3785EUF-1#PBF | 功能描述:IC REG CTRLR BST PWM VM 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) |
| LTC3785EUF-1#TRPBF | 功能描述:IC REG CTRLR BST PWM VM 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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:-40°C ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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