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参数资料
| 型号： | LT3742EUF#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 8/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-QFN |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 2 |
| 频率 - 最大： | 560kHz |
| 占空比： | 100% |
| 电源电压： | 4 V ~ 30 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： | 24-WFQFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
LT3742
OPERATION
The LT3742 is a dual, constant frequency, current mode
DC/DC step-down controller. The two controllers in each
device share some common circuitry including protec-
tion circuitry, the internal bias supply, voltage reference,
master oscillator and the gate drive boost regulator. The
Block Diagram shows the shared common circuitry and
the independent circuitry for both DC/DC controllers.
Important protection features included in the LT3742 are
undervoltage lockout and thermal shutdown. When either
of these conditions exist, the gate drive bias regulator and
both DC/DC controllers are disabled and both RUN/SS pins
are discharged to 0.5V to get ready for a new soft-start
cycle. Undervoltage lockout (UVLO) is programmed using
two external resistors. When the UVLO pin drops below
1.25V, a 3μA current sink is activated to provide program-
mable hysteresis for the UVLO function. A separate, less
accurate, internal undervoltage lockout will disable the
LT3742 when V IN is less than 2.5V.
The gate drive boost regulator is enabled when all internal
fault conditions have been cleared. This regulator uses
both an internal NPN power switch and Schottky diode to
generate a voltage at the BIAS pin that is 7V higher than
the input voltage. Both DC/DC controllers are disabled until
the BIAS voltage has reached ~90% of its final regulation
voltage. This ensures that sufficient gate drive to fully
enhance the external MOSFETs is present before the driver
is allowed to turn on.
The master oscillator runs at 1MHz and clocks the gate
drive boost regulator at this frequency. The master oscilla-
tor also generates two 500kHz clocks, 180° out of phase,
for the DC/DC controllers.
A power good comparator pulls the PG pin low whenever
the FB pin is not within ±10% of the 800mV internal
reference voltage. PG is the open-collector output of an
NPN that is off when the FB pin is in regulation, allowing
an external resistor to pull the PG pin high. This power
good indication is valid only when the device is enabled
(RUN/SS is high) and V IN is 4V or greater.
The LT3742 enables each controller independently when its
RUN/SS pin is above 0.5V and each controller generates
its own soft-start ramp. During start-up, the error ampli-
fier compares the FB pin to the soft-start ramp instead of
the precision 800mV reference, which slowly raises the
output voltage until it reaches its resistor programmed
regulation point. Control of the inductor current is strictly
maintained until the output voltage is reached. The LT3742
is ideal for applications where both DC/DC controllers need
to operate separately.
A pulse from the 500kHz oscillator sets the RS flip-flop
and turns on the external N-channel MOSFET. Current in
the switch and the external inductor begins to increase.
When this current reaches a level determined by the control
voltage (V C ), the PWM comparator resets the flip-flop,
turning off the MOSFET. The current in the inductor then
flows through the external Schottky diode and begins to
decrease. This cycle begins again at the next set pulse from
the slave oscillator. In this way, the voltage at the V C pin
controls the current through the inductor to the output.
The internal error amplifier regulates the output voltage
by continually adjusting the V C pin voltage. Direct control
of the peak inductor current on a cycle-by-cycle basis is
managed by the current sense amplifier. Because the induc-
tor current is constantly monitored, the devices inherently
provide excellent output short-circuit protection.
3742fa
8
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相关代理商/技术参数 |
参数描述 |
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| LT3743 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Current Synchronous Step-Down LED Driver with Three-State Control |
| LT3743_10 | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Current Synchronous Step-Down LED Driver with Three-State Control |
| LT3743EFE#PBF | 功能描述:IC LED DVR HP CONST CURR 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C |
| LT3743EFE#PBF | 制造商:Linear Technology 功能描述:IC LED DRIVER BUCK TSSOP-28 |
| LT3743EFE#TRPBF | 功能描述:IC LED DVR SYNC STEPDOWN 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND |
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