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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： | 4/23页 |
| 文件大小： | 720K |
| 代理商： | L6668 |
L6668
12/23
4
Application Information
The L6668 is a versatile current-mode PWM controller specific for offline fixed-frequency, peak-current-
mode-controlled flyback converters.
The device is able to operate in different modes (fig. 34), depending on the converter's load conditions:
1) Fixed frequency at heavy load. In this region the IC operates exactly like a standard current mode control
chip: a relaxation oscillator, externally programmable with a capacitor and a resistor, generates a sawtooth
and releases a clock pulse during the falling edge of the sawtooth; the power switch is turned on by the clock
pulses and is turned off by the control loop.
2) Frequency-foldback mode at medium and light load. As the load is reduced the oscillator frequency is re-
duced as well by slowing down the charge of the timing capacitor proportionally to the load itself.
3) Burst-mode control with no or very light load. When the load is extremely light or disconnected, the converter
will enter a controlled on/off operation with constant peak current. A load decrease will be then translated
into a frequency reduction, which can go down even to few hundred hertz, thus minimizing all frequency-
related losses and making it easier to comply with energy saving regulations. Being the peak current very
low, no issue of audible noise arises.
Figure 34. Multi-mode operation of the L6668
4.1 High-voltage start-up generator
Figure 35 shows the internal schematic of the high-voltage start-up generator (HV generator). It is made
up of a high-voltage N-channel FET, whose gate is biased by a 15 M
resistor, with a temperature-com-
pensated current generator connected to its source.
Figure 35. High-voltage start-up generator: internal schematic
The HV generator is physically located on a separate chip, made with BCD off-line technology able to with-
stand 700V, controlled by a low-voltage chip, where all of the control functions reside.
0
fsw
Pin
Fixed-frequency mode
Frequency foldback mode
Pinmax
B
u
rs
tm
o
de
L6668
15 M
GND
HV
Vcc
5
3
1
Icharge
Vcc_OK
IHV
CONTROL
HV_EN
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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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