LM2585S-5.0 National Semiconductor, LM2585S-5.0 Datasheet - Page 17

• Manufacturer Part Number: LM2585S-5.0
• Description: DC/DC Converter IC
• Manufacturer: National Semiconductor

Specifications of LM2585S-5.0

• Input Voltage: 40V
• Output Voltage: 5V
• No. Of Pins: 5
• Termination Type: SMD
• Mounting Type: Through Hole
• Output Current Max: 0.5A
• Peak Reflow Compatible (260 C): No
• Supply Voltage Max: 40V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Step-Up (Boost) Regulator Operation
Figure 30 shows the LM2585 used as a step-up (boost)
regulator. This is a switching regulator that produces an out-
put voltage greater than the input supply voltage.
A brief explanation of how the LM2585 Boost Regulator
works is as follows (refer to Figure 30 ). When the NPN
switch turns on, the inductor current ramps up at the rate of
V
By adding a small number of external components (as shown in Figure 30 ), the LM2585 can be used to produce a regulated output voltage that is greater than
the applied input voltage. The switching waveforms observed during the operation of this circuit are shown in Figure 31 . Typical performance of this regulator is
shown in Figure 32 .
A: Switch Voltage, 10 V/div
B: Switch Current, 2 A/div
C: Inductor Current, 2 A/div
D: Output Ripple Voltage,
100 mV/div, AC-Coupled
Horizontal: 2 µs/div
IN
/L, storing energy in the inductor. When the switch turns
FIGURE 32. V
FIGURE 31. Switching Waveforms
FIGURE 30. 12V Boost Regulator
OUT
Response to Load Current Step
17
off, the lower end of the inductor flies above V
its current through diode (D) into the output capacitor (C
at a rate of (V
tor during the switch on time is transferred to the output dur-
ing the switch off time. The output voltage is controlled by
adjusting the peak switch current, as described in the flyback
regulator section.
OUT
DS012515-49
− V
DS012515-50
IN
)/L. Thus, energy stored in the induc-
DS012515-48
IN
, discharging
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OUT
)