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参数资料
| 型号： | L6668 |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | 0.8 A SWITCHING CONTROLLER, 105 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | LEAD FREE, SOP-16 |
| 文件页数： | 8/23页 |
| 文件大小： | 720K |
| 代理商： | L6668 |
L6668
16/23
Figure 40. Load-dependent operating modes: timing diagram
The operating range of the voltage V(SKIPADJ) is practically limited upwards by the onset of audible
noise: typically, with a voltage above 2-2.1V some noise can be heard under some line/load conditions. If,
instead, V(SKIPADJ) is set below the low saturation value of the PWM control voltage (1.4V typ.) burst-
mode operation will never take place. Always bias the pin at some voltage, a floating pin will result in
anomalous behavior. The SKIPADJ pin doubles its function: if the voltage is pulled below 0.8V the IC is
disabled completely, except for the externally available reference voltage VREF, and its quiescent con-
sumption reduced. The soft-start capacitor is discharged so that, when the voltage on the SKIPADJ pin is
pulled above 0.8V, the chip is soft-started just like exiting from UVLO. This function is useful for some kind
of remote ON/OFF control. The comparator referenced to 0.8V does not have hysteresis; hence make
sure that the voltage on the pin does not linger on the threshold to prevent uncertain behavior.
4.4 PWM control Block
The device is specific for secondary feedback. Typically, there is a TL431 at the secondary side and an
optocoupler that transfers output voltage information to the PWM control at the primary side, crossing the
isolation barrier. The PWM control input (pin #10, COMP) is driven directly by the phototransistor's col-
lector (the emitter is grounded to GND) to modulate the duty cycle.
4.5 Current Comparator, PWM Latch and Hiccup-mode OCP
The current comparator senses the voltage across the current sense resistor (Rs) on pin 12 (ISEN) and,
by comparing it with the programming signal derived form the control voltage on pin 10 (COMP), deter-
mines the exact time when the external MOSFET is to be switched off. The PWM latch avoids spurious
switching of the MOSFET, which might result from the noise generated ("double-pulse suppression").
OUT
V(SKIPADJ)
t
COMP
50 mV
hyster.
3.0V
Fix. Freq.
Mode
Frequency Foldback Mode
Burst-mode
fosc
Fix. Freq.
Mode
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L6668_06 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:SMART PRIMARY CONTROLLER |
| L6668B2 | 功能描述:电流型 PWM 控制器 POWER SUPPLY RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| L6668TR | 功能描述:电流型 PWM 控制器 SMART CONTROLLER RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| L667 | 制造商:BURNDY 功能描述:L-DIE |
| L-667 | 制造商:RHOMBUS-IND 制造商全称:Rhombus Industries Inc. 功能描述:Common Mode Inductor For DC/DC Power supply |
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