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| 型号： | LM5020SDX-2/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 7/17页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK INV 10LLP |
| 标准包装： | 4,500 |
| 系列： | PowerWise® |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 50% |
| 电源电压： | 13 V ~ 90 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 是 |
| 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： | 10-WDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 其它名称： | LM5020SDX-2 |
SNVS275F – MAY 2004 – REVISED APRIL 2006
DETAILED OPERATING DESCRIPTION
The LM5020 High Voltage PWM controller contains all of the features needed to implement single ended primary
power converter topologies. The LM5020 includes a high-voltage startup regulator that operates over a wide
input range to 100V. The PWM controller is designed for high speed capability including an oscillator frequency
range to 1MHz and total propagation delays less than 100ns. Additional features include an error amplifier,
precision reference, line under-voltage lockout, cycle-by-cycle current limit, slope compensation, softstart,
oscillator sync capability and thermal shutdown. The functional block diagram of the LM5020 is shown in Figure
1. The LM5020 is designed for current-mode control power converters, which require a single drive output, such
as Flyback and Forward topologies. The LM5020 provides all of the advantages of current-mode control
including line feed-forward, cycle-by-cycle current limiting and simplified loop compensation .
High Voltage Start-Up Regulator
The LM5020 contains an internal high voltage startup regulator, that allows the input pin (Vin) to be connected
directly to line voltages as high as 100V. The regulator output is internally current limited to 15mA. When power
is applied, the regulator is enabled and sources current into an external capacitor connected to the V CC pin. The
recommended capacitance range for the Vcc regulator is 0.1μF to 100μF. When the voltage on the V CC pin
reaches the regulation level of 7.7V, the controller output is enabled. The controller will remain enabled until V CC
falls below 6V.
In typical applications, a transformer auxiliary winding is connected through a diode to the V CC pin. This winding
should raise the V CC voltage above 8V to shut off the internal startup regulator. Powering V CC from an auxiliary
winding improves conversion efficiency while reducing the power dissipated in the controller. The external V CC
capacitor must be selected such that the capacitor maintains the Vcc voltage greater than the V CC UVLO falling
threshold (6V) during the initial start-up. During a fault condition when the converter auxiliary winding is inactive,
external current draw on the V CC line should be limited such that the power dissipated in the start-up regulator
does not exceed the maximum power dissipation capability of the controller.
An external start-up or other bias rail can be used instead of the internal start-up regulator by connecting the V CC
and the Vin pins together and feeding the external bias voltage (8-15V) to the two pins.
Line Under Voltage Detector
The LM5020 contains a line Under Voltage Lock Out (UVLO) circuit. An external set-point voltage divider from
Vin to GND sets the operational range of the converter. The resistor divider must be designed such that the
voltage at the UVLO pin is greater than 1.25V when Vin is in the desired operating range. If the under voltage
threshold is not met, all functions of the controller are disabled and the controller remains in a low power standby
state.
UVLO hysteresis is accomplished with an internal 20μA current source that is switched on or off into the
impedance of the set-point divider. When the UVLO threshold is exceeded, the current source is activated to
instantly raise the voltage at the UVLO pin. When the UVLO pin voltage falls below the 1.25V threshold the
current source is turned off, causing the voltage at the UVLO pin to fall. The UVLO pin can also be used to
implement a remote enable / disable function. If an external transistor pulls the UVLO pin below the 1.25V
threshold, the converter is disabled.
Error Amplifier
An internal high gain error amplifier is provided within the LM5020. The amplifier's non-inverting input is internally
set to a fixed reference voltage of 1.25V. The inverting input is connected to the FB pin. In non-isolated
applications, the power converter output is connected to the FB pin via voltage scaling resistors. Loop
compensation components are connected between the COMP and FB pins. For most isolated applications the
error amplifier function is implemented on the secondary side of the converter and the internal error amplifier is
not used. The internal error amplifier is configured as an open drain output and can be disabled by connecting
the FB pin to ground. An internal 5K pull-up resistor between a 5V reference and COMP can be used as the pull-
up for an optocoupler in isolated applications.
Copyright ? 2004–2006, Texas Instruments Incorporated
Product Folder Links: LM5020
7
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5021 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:AC-DC Current Mode PWM Controller |
| LM5021-1QDGKRQ1 | 功能描述:Converter Offline Flyback Topology 150kHz ~ 1MHz 8-VSSOP 制造商:texas instruments 系列:汽车级，AEC-Q100 包装:剪切带（CT） 零件状态:有效 输出隔离:隔离 内部开关:无 电压 - 击穿:- 拓扑:回扫 电压 - 启动:20V 电压 - 电源（Vcc/Vdd）:8 V ~ 30 V 占空比:80% 频率 - 开关:150kHz ~ 1MHz 功率（W）:- 故障保护:限流，过载 控制特性:频率控制，软启动，同步 工作温度:-40°C ~ 125°C （TJ） 封装/外壳:8-TSSOP，8-MSOP（0.118"，3.00mm 宽） 供应商器件封装:8-VSSOP 安装类型:表面贴装 标准包装:1 |
| LM5021MM-1 | 功能描述:电流型 PWM 控制器 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 |
| LM5021MM-1/NOPB | 功能描述:电流型 PWM 控制器 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 |
| LM5021MM-1/S7003080 | 制造商:Texas Instruments 功能描述:AC-DC Current Mode PWM Controller |
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