LM3578AN National Semiconductor, LM3578AN Datasheet - Page 18

• Manufacturer Part Number: LM3578AN
• Description: DC/DC Converter IC
• Manufacturer: National Semiconductor

Specifications of LM3578AN

• Input Voltage: 40V
• Output Voltage: 1V
• No. Of Pins: 8
• Mounting Type: Through Hole
• Output Voltage Min: -1V
• Voltage Regulator Type: Switching
• Output Current Max: 750mA
• Peak Reflow Compatible (260 C): No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Typical Applications
A minimum value for an ideal output capacitor C3, could be
calculated as C = I
the transistor on time (typically 0.4/f
to-peak output voltage ripple. A larger output capacitor than
this theoretical value should be used since electrolytics have
poor high frequency performance. Experience has shown
that a value from 5 to 10 times the calculated value should
be used.
For good efficiency, the diodes must have a low forward
voltage drop and be fast switching. 1N5819 Schottky diodes
work well.
o
x t/∆V where I
o
osc
(Continued)
is the load current, t is
), and ∆V is the peak-
18
Transformer selection should be picked for an output tran-
sistor “on” time of 0.4/f
enough to prevent the output transistor switch from ramping
higher than the transistor’s rating of 750 mA. Pulse Engi-
neering (San Diego, Calif.) and Renco Electronics, Inc.
(Deer Park, N.Y.) can provide further assistance in selecting
the proper transformer for a specific application need. The
transformer used in Figure 23 was a Pulse Engineering
PE-64287.
osc
, and a primary inductance high