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: 10/12页
文件大小: 231K
代理商: LM5007MMEP
High Voltage Bias Regulator (Continued)
Over-Voltage Comparator
The over-voltage comparator is provided to protect the out-
put from overvoltage conditions due to sudden input line
voltage changes or output loading changes. The over-
voltage comparator monitors the FB pin versus an internal
2.875V reference (OV_REF). If the voltage at FB rises above
OV_REF the comparator immediately terminates the buck
switch on time pulse.
On Time Generator and Shutdown
The on time of the LM5007EP is set inversely proportional to
the input voltage by an external resistor connected between
R
ON and Vin. The RON terminal is a low impedance input
biased at approximately 1.5V. Thus the current through the
resistor and into the R
ON terminal is approximately propor-
tional to Vin and used internally to control the on timer. This
scheme of input voltage feed-forward hysteretic operation
achieves nearly constant operational frequency over varying
line and load conditions. The on time equation for the
LM5007EP is :
Ton=1.42x10
-10 xR
ON /VIN
The R
ON pin of the LM5007EP also provides a shutdown
function which disables the regulator and significantly de-
creases quiescent power dissipation. By pulling the R
ON pin
to below 0.7V logic threshold activates the low power shut-
down mode. The V
IN quiescent current in the shutdown
mode is approximately 100A internal to the LM5007EP plus
the current in the R
ON resistor.
20093906
FIGURE 2. Self Biased Configuration
LM5007EP
Enhanced
Plastic
www.national.com
7
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