- 您现在的位置：买卖IC网 > PDF目录30756 > LM5007MMEP (NATIONAL SEMICONDUCTOR CORP) SWITCHING REGULATOR, PDSO8 PDF资料下载
参数资料
| 型号： | LM5007MMEP |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, PDSO8 |
| 封装： | PLASTIC, MSOP-8 |
| 文件页数： | 11/12页 |
| 文件大小： | 231K |
| 代理商： | LM5007MMEP |
On Time Generator and Shutdown (Continued)
Current Limit
The LM5007EP contains an intelligent current limit off timer
intended to reduce the foldback characteristic inherent with
fixed off-time over-current protection. If the current in the
Buck switch exceeds 725mA the present cycle on time is
immediately terminated (cycle by cycle current limit). Follow-
ing the termination of the cycle a non-resetable current limit
off timer is initiated. The duration of the off time is a function
of the external resistor (R
CI) and the FB pin voltage. When
the FB pin voltage equals zero, the current limit off time is
internally preset to 17uS. This condition occurs in short
circuit operation when a maximum amount of off time is
required.
In cases of overload (not complete short circuit) the current
limit off time can be reduced as a function of the output
voltage (measured at the FB pin). Reducing the off time with
smaller overloads reduces the amount of foldback and also
reduces the initial start-up time. The current limit off time for
a given FB pin voltage and R
CI resistor can be calculated by
the following equation:
Toff=10
-5 / (0.59 + (V
FB /7.22x10
-6 xR
CL))
Applications utilizing low resistance inductors and/or a low
voltage drop rectifier may require special evaluation at high
line, short circuit conditions. In this special case the preset
17uS (FB = 0V) off time may be insufficient to balance the
inductor volt*time product. Additional inductor resistance,
output resistance or a larger voltage drop rectifier may be
necessary to balance the inductor cycle volt*time product
and limit the short circuit current.
N - Channel Buck Switch and
Driver
The LM5007EP integrates an N-Channel Buck switch and
associated floating high voltage gate driver. This gate driver
circuit works in conjunction with an external bootstrap ca-
pacitor and an internal high voltage diode. The bootstrap
capacitor is charged by V
CC through the internal high voltage
diode. A 0.01uF ceramic capacitor connected between the
BST pin and SW pin is recommended.
During each cycle when the Buck switch turns off, the SW
pin is approximately 0V. When the SW pin voltage is low, the
bootstrap capacitor will be charged from Vcc through the
internal diode. The minimum off timer, set to 300ns, ensures
that there will be a minimum interval every cycle to recharge
the bootstrap capacitor.
An external re-circulating diode from the SW pin to ground is
necessary to carry the inductor current after the internal
Buck switch turns off. This external diode must be of the
Ultra-fast or Schottky type to reduce turn-on losses and
current over-shoot. The reverse voltage rating of the re-
circulating diode must be greater than the maximum line
input voltage.
Thermal Protection
Internal Thermal Shutdown circuitry is provided to protect the
integrated circuit in the event the maximum junction tem-
perature is exceeded. When thermal protection is activated,
typically at 165 degrees Celsius, the controller is forced into
a low power reset state, disabling the output driver. This
feature is provided to prevent catastrophic failures from ac-
cidental device overheating.
20093907
FIGURE 3. Shutdown Implementation
LM5007EP
Enhanced
Plastic
www.national.com
8
相关PDF资料 |
PDF描述 |
|---|---|
| LM5060MMX | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10 |
| LM5060MM | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10 |
| LM556J/883C | DUAL RECTANGULAR, TIMER, CDIP14 |
| LM556J/883B | DUAL RECTANGULAR, TIMER, CDIP14 |
| LM556J/NOPB | DUAL RECTANGULAR, TIMER, CDIP14 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM5007MMX | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM5007MMX/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM5007MMXNOPB | 制造商:National Semiconductor 功能描述:Conv DC-DC Single Step Down 9V to 75V 8-Pin MSOP T/R |
| LM5007SD | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LM5007SD/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
发布紧急采购，3分钟左右您将得到回复。