LM5007EVAL National Semiconductor, LM5007EVAL Datasheet - Page 7

• Manufacturer Part Number: LM5007EVAL
• Description: EVALUATION BOARD KIT, LM5007 SERIES
• Manufacturer: National Semiconductor

Specifications of LM5007EVAL

• Svhc: No SVHC (15-Dec-2010)
• Development Tool Type: Evaluation Board
• Kit Features: 12V To 75V Input Range, 90% Measured Efficiency, 10V Output Voltage, 400mA Output Current
• Silicon Manufacturer: National Semiconductor
• Kit Contents: Board, Datasheet
• Features: Thermal Shutdown, Intelligent Current Limit Protection, Highly Efficient Operation

High Voltage Bias Regulator
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 LM5007 is set inversely proportional to
the input voltage by an external resistor connected between
Ron and Vin. The Ron terminal is a low impedance input
biased at approximately 1.5V. Thus the current through the
FIGURE 2. Self Biased Configuration
(Continued)
7
resistor and into the Ron 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
LM5007 is :
The R
tion which disables the regulator and significantly decreases
quiescent power dissipation. By pulling the R
0.7V logic threshold activates the low power shutdown
mode. The V
approximately 100µA internal to the LM5007 plus the current
in the R
ON
ON
pin of the LM5007 also provides a shutdown func-
resistor.
IN
Ton = 1.42 x 10
quiescent current in the shutdown mode is
20078306
-10
x R
ON
/ V
IN
ON
pin to below
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