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参数资料
| 型号： | LM5025 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | Active Clamp Voltage Mode PWM Controller |
| 中文描述： | 有源钳位电压模式PWM控制器 |
| 文件页数： | 3/16页 |
| 文件大小： | 316K |
| 代理商： | LM5025 |
PWM Outputs (Continued)
Compound Gate Drivers
The LM5025 contains two unique compound gate drivers,
which parallel both MOS and Bipolar devices to provide high
drive current throughout the entire switching event. The Bi-
polar device provides most of the drive current capability and
provides a relatively constant sink current which is ideal for
driving large power MOSFETs. As the switching event nears
conclusion and the Bipolar device saturates, the internal
MOS device continues to provide a low impedance to com-
pete the switching event.
During turn-off at the Miller plateau region, typically around
2V - 3V, is where gate driver current capability is needed
most. The resistive characteristics of all MOS gate drivers
are adequate for turn-on since the supply to output voltage
differential is fairly large at the Miller region. During turn-off
however, the voltage differential is small and the current
source characteristic of the Bipolar gate driver is beneficial to
provide fast drive capability.
20086913
PWM Comparator
The PWM comparator compares the ramp signal (RAMP) to
the loop error signal (COMP). This comparator is optimized
for speed in order to achieve minimum controllable duty
cycles. The internal 5k
pull-up resistor, connected between
the internal 5V reference and COMP, can be used as the
pull-up for an optocoupler. The comparator polarity is such
that 0V on the COMP pin will produce a zero duty cycle on
both gate driver outputs.
Volt Second Clamp
The Volt x Second Clamp comparator compares the ramp
signal (RAMP) to a fixed 2.5V reference. By proper selection
of RFF and CFF, the maximum ON time of the main switch
can be set to the desired duration. The ON time set by Volt
x Second Clamp varies inversely with the line voltage be-
cause the RAMP capacitor is charged by a resistor con-
nected to Vin while the threshold of the clamp is a fixed
voltage (2.5V). An example will illustrate the use of the Volt x
Second Clamp comparator to achieve a 50% duty cycle limit,
at 200KHz, at a 48V line input: A 50% duty cycle at a 200KHz
requires a 2.5s of ON time. At 48V input the Volt x Second
product is 120V x s (48V x 2.5s). To achieve this clamp
level:
R
FF xCFF =VIN xTON / 2.5V
48 x 2.5 / 2.5 = 48
Select C
FF = 470pF
R
FF = 102k
The recommended capacitor value range for CFF is 100pF
to 1000pF.
The C
FF ramp capacitor is discharged at the conclusion of
every cycle by an internal discharge switch controlled by
either the internal clock or by theVxS Clamp comparator,
whichever event occurs first.
Current Limit
The LM5025 contains two modes of over-current protection.
If the sense voltage at the CS1 input exceeds 0.25V the
present power cycle is terminated (cycle-by-cycle current
limit). If the sense voltage at the CS2 input exceeds 0.25V,
the controller will terminate the present cycle, discharge the
softstart capacitor and reduce the softstart current source to
1A. The softstart (SS) capacitor is released after being fully
discharged and slowly charges with a 1A current source.
When the voltage at the SS pin reaches approximately 1V,
20086912
FIGURE 1.
LM5025
www.national.com
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5025A | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Active Clamp Voltage Mode PWM Controller |
| LM5025AEVAL | 功能描述:BOARD EVALUATION LM5025A RoHS:否 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:PowerWise® 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| LM5025AEVAL/NOPB | 功能描述:电源管理IC开发工具 LM5025A EVAL BOARD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM5025AMTC | 功能描述:电压模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| LM5025AMTC/NOPB | 功能描述:电压模式 PWM 控制器 100V Forward Active Clamp RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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