lm5015mhx National Semiconductor Corporation, lm5015mhx Datasheet - Page 20

• Manufacturer Part Number: lm5015mhx
• Description: High Voltage Monolithic Two-switch Forward Dc-dc Regulator
• Manufacturer: National Semiconductor Corporation

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48V ISOLATED TWO-SWITCH FORWARD
The Isolated Two-Switch Forward converter shown in Figure
13 utilizes a 1.24V voltage reference (LMV431A) located on
the isolated secondary side for the regulation set-point. The
LM5015 internal error amplifier is disabled by grounding the
FB pin. The LMV431A controls the current through the opto-
ISOLATED TWO-SWITCH FLYBACK
The Isolated Two-Switch Flyback converter shown in Figure
14 utilizes a 1.24V voltage reference (LMV431A) located on
the isolated secondary side for the regulation set-point. The
LM5015 internal error amplifier is disabled by grounding the
FB pin. The LMV431A controls the current through the opto-
coupler LED, which sets the COMP pin voltage. The output is
+5V at 2.5A and the input voltage ranges from 36V to 72V.
The switching frequency is 300 kHz. The Flyback converter
FIGURE 13. Isolated Two-Switch Forward
FIGURE 14. Isolated Two-Switch Flyback
20
coupler LED, which sets the COMP pin voltage. The output is
+5V at 2.5A and the input voltage ranges from 36V to 72V.
The switching frequency is 300 kHz. The functions of the EN
and SYNC inputs are the same as in the previous example
circuit.
is less complex than the previous Forward converter example
in Figure 13. However, the Flyback converter produces higher
input and output ripples of voltage and currents, and lower
conversion efficiency by about 2%. The functions of the EN
and SYNC inputs are the same as in the previous example
circuits.
This circuit can be used with the LM5073 for a low cost iso-
lated Power over Ethernet (PoE) Power Device (PD) appli-
cation that does not require a discrete power MOSFET.
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