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参数资料
| 型号： | LTC3783IFE#TR |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 1 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | 4.40 MM, PLASTIC, TSSOP-16 |
| 文件页数： | 24/24页 |
| 文件大小： | 250K |
| 代理商： | LTC3783IFE#TR |
LTC3783
9
3783fb
OPERATION
Main Control Loop
The LTC3783 is a constant frequency, current mode con-
troller for PWM LED as well as DC/DC boost, SEPIC and
yback converter applications. In constant current LED
applications, the LTC3783 provides an especially wide PWM
dimming range due to its unique switching scheme, which
allows PWM pulse widths as short as several converter
switching periods.
For voltage feedback circuit operation (dened by VFBP ≤
1.23V), please refer to the Block Diagram of the IC and the
Typical Application on the rst page of this data sheet. In
normal operation with PWMIN high, the power MOSFET
is turned on (GATE goes high) when the oscillator sets
the PWM latch, and is turned off when the ITRIP current
comparator resets the latch. Based on the error voltage
represented by (VFBP – VFBN), the error amplier output
signal at the ITH pinsetstheITRIPcurrentcomparatorinput
threshold. When the load current increases, a fall in the
FBN voltage relative to the reference voltage at FBP causes
the ITH pin to rise, causing the ITRIP current comparator
to trip at a higher peak inductor current value. The average
inductor current will therefore rise until it equals the load
current, thereby maintaining output regulation.
When PWMIN goes low, PWMOUT goes low, the ITH switch
opens and GATE switching is disabled. Lowering PWMOUT
and disabling GATE causes the output capacitor COUT to
hold the output voltage constant in the absence of load
current. Opening the ITH switch stores the correct load
current value on the ITH capacitor CITH. As a result, when
PWMIN goes high again, both ITH and VOUT are instantly
at the appropriate levels.
In voltage feedback operation, an overvoltage compara-
tor, OV, senses when the OV/FB pin exceeds the reference
voltage by 7% and provides a reset pulse to the main RS
latch. Because this RS latch is reset-dominant, the power
MOSFET is actively held off for the duration of an output
overvoltage condition.
For constant current/constant voltage regulation operation
(dened by VFBP > 2.5V), please refer to the Block Diagram
of the IC and Figure 11. Loop operation is similar to the
voltage feedback, except FBP and FBN now sense the
voltage across sense resistor RL in series with the load.
The ITH pin now represents the error from the desired dif-
ferential set voltage, from 10mV to 100mV, for ILIM values
of 0.123V to 1.23V. That is, with VILIM = 1.23V, the loop
will regulate such that VFBP – VFBN = 100mV; lower values
of ILIM attenuate the difference proportionally. PWMIN is
still functional as above, but will only work properly if load
current can be disconnected by the PWMOUT signal.
In constant current/constant voltage operation, the OV/FB
pin becomes a voltage feedback pin, which causes the loop
to regulate such that VOV/FB = 1.23V, provided the above
current-sense voltage is not reached. In this way, the loop
regulates either voltage or current, whichever parameter
hits its preset limit rst.
The nominal operating frequency of the LTC3783 is pro-
grammed using a resistor from the FREQ pin to ground
and can be controlled over a 20kHz to 1MHz range. In
addition, the internal oscillator can be synchronized to an
external clock applied to the SYNC pin and can be locked
to a frequency between 100% and 130% of its nominal
value. When the SYNC pin is left open, it is pulled low by
an internal 100k resistor. With no load, or an extremely
light one, the controller will skip pulses in order to maintain
regulation and prevent excessive output ripple.
The RUN pin controls whether the IC is enabled or is in a
low current shutdown state. A micropower 1.248V refer-
ence and RUN comparator allow the user to program the
supply voltage at which the IC turns on and off (the RUN
comparator has 100mV of hysteresis for noise immunity).
With the RUN pin below 1.248V, the chip is off and the
input supply current is typically only 20μA.
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相关代理商/技术参数 |
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| 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) |
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| LTC3785EUFPBF | 制造商:Linear Technology 功能描述:10V Synch Buck-Boost Controller LTC3785 |
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