参数资料
| 型号： | LT3742EUF#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 9/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-QFN |
| 标准包装： | 91 |
| 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： | 管件 |
| 产品目录页面： | 1332 (CN2011-ZH PDF) |
LT3742
APPLICATIONS INFORMATION
Soft-Start and Shutdown
The RUN/SS (Run/Soft-Start) pins are used to enable each
controller independently, and to provide a user-program-
mable soft-start function that reduces the peak input
current and prevents output voltage overshoot during
start-up. To disable either controller, pull its RUN/SS pin
to ground with an open-drain or open-collector device.
If both RUN/SS pins are pulled to ground, the LT3742
is placed in shutdown mode, and quiescent current is
reduced to 20μA. Internal 1μA current sources pull up on
each RUN/SS pin, and when either pin reaches 0.5V, that
controller is enabled, along with the internal bias supply,
gate drive boost regulator, voltage reference and master
oscillator. If both outputs are always enabled together,
one soft-start capacitor can be used with both RUN/SS
pins tied together.
The Benefits of Soft-Start
When a capacitor is tied from the RUN/SS pin to ground,
the internal 1μA pull-up current source generates a volt-
age ramp on this pin. During start-up, the error amplifier
V OUT
5V/DIV
I L
2A/DIV
compares the FB pin to this ramp instead of to the 800mV
reference; this slowly and smoothly increases the output
voltage to its final value, while maintaining control of the
inductor current. Always check the inductor current and
output voltage waveforms to ensure that the programmed
soft-start time is long enough. A new soft-start cycle will
be initiated whenever V IN drops low enough to trigger
undervoltage lockout (programmed using the UVLO pin),
or the LT3742 die temperature exceeds thermal shutdown.
A typical value for the soft-start capacitor is 1nF.
Soft-start is strongly recommended for all LT3742 appli-
cations, as it provides the least amount of stress on the
external power MOSFET and catch diode. Without soft-start,
both of these components will see the maximum current
limit every start-up cycle. Figures 1a and 1b show start-
up waveforms with and without soft-start for the circuit
on the front page. Notice the large inductor current spike
and the output voltage overshoot when soft-start is not
used. While this may be acceptable for some systems, the
addition of a single capacitor dramatically improves the
start-up behavior of each DC/DC controller.
V OUT
5V/DIV
I L
2A/DIV
0.5ms/DIV
3742 F01a
0.5ms/DIV
3742 F01b
Figure 1a. Start-Up Waveforms Without Soft-Start
Figure 1b. Start-Up Waveforms with 1nF Soft-Start Capacitor
3742fa
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3742EUF-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual, 2-Phase Step-Down Switching Controller |
| 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 |
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