参数资料
型号: LM2586-ADJMDC
厂商: NATIONAL SEMICONDUCTOR CORP
元件分类: 稳压器
英文描述: 7 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC
封装: DIE
文件页数: 14/32页
文件大小: 858K
代理商: LM2586-ADJMDC
Typical Boost Regulator Applications (Continued)
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 Application Hints.
Application Hints
LM2586 SPECIAL FEATURES
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 op-
eration, 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 A of supply current
(16 A to V
IN and 40 A to the ON /OFF pin). To turn the de-
vice 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).
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 fre-
quency 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 se-
lection and compensation component values.
DS012516-57
FIGURE 37. +24V to +48V Boost Regulator
DS012516-58
FIGURE 38. Shutdown Operation
R
SET(k)
Frequency (kHz)
Open
100
200
125
47
150
33
175
22
200
FIGURE 39. Frequency Setting Resistor Guide
www.national.com
21
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