551011367-051 National Semiconductor, 551011367-051 Datasheet - Page 24

• Manufacturer Part Number: 551011367-051
• Description: BOARD WEBENCH BUILD IT LM2586/88
• Manufacturer: National Semiconductor
• Series: WEBENCH® Buildit Boardr

Specifications of 551011367-051

• Main Purpose: DC/DC, Step Up
• Regulator Topology: Boost
• Board Type: Bare (Unpopulated)
• Utilized Ic / Part: LM2586, LM2588
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Current - Output: -
• Voltage - Output: -
• Voltage - Input: -
• Power - Output: -
• Frequency - Switching: -
• Outputs And Type: -
• Lead Free Status / Rohs Status: Not Compliant
• Other names: *551011367-051

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Typical Boost Regulator Applications
Note 24: The LM2586 will require a heat sink in these applications. The size
of the heat sink will depend on the maximum ambient temperature. To
calculate the thermal resistance of the IC and the size of the heat sink
needed, see the “Heat Sink/Thermal Considerations” section in the Applica-
tion Hints.
SHUTDOWN CONTROL
A feature of the LM2586 is its ability to be shut down using
the ON /OFF pin (pin 1). This feature conserves input power
by turning off the device when it is not in use. For proper
operation, an isolation diode is required (as shown in Figure
38).
The device will shut down when 3V or greater is applied on
the ON /OFF pin, sourcing current into pin 1. In shut down
mode, the device will draw typically 56 µA of supply current
(16 µA to V
device back on, leave pin 1 floating, using an (isolation)
diode, as shown in Figure 38 (for normal operation, do not
source or sink current to or from this pin — see the next
section).
IN
and 40 µA to the ON /OFF pin). To turn the
FIGURE 37. +24V to +48V Boost Regulator
FIGURE 38. Shutdown Operation
24
(Continued)
Application Hints
LM2586 SPECIAL FEATURES
FREQUENCY ADJUSTMENT
The switching frequency of the LM2586 can be adjusted with
the use of an external resistor. This feature allows the user to
optimize the size of the magnetics and the output capaci-
tor(s) by tailoring the operating frequency. A resistor con-
nected from pin 1 (the Freq. Adj. pin) to ground will set the
switching frequency from 100 kHz to 200 kHz (maximum).
As shown in Figure 38, the pin can be used to adjust the
frequency while still providing the shut down function. A
curve in the Performance Characteristics Section graphs the
resistor value to the corresponding switching frequency. The
table in Figure 39 shows resistor values corresponding to
commonly used frequencies.
However, changing the LM2586’s operating frequency from
its nominal value of 100 kHz will change the magnetics
selection and compensation component values.
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