LM5071HEEVAL National Semiconductor, LM5071HEEVAL Datasheet - Page 9

• Manufacturer Part Number: LM5071HEEVAL
• Manufacturer: National Semiconductor

Specifications of LM5071HEEVAL

• Lead Free Status / Rohs Status: Not Compliant

Performance Characteristics
Horizontal Resolution: 1 µs/Div.
Trace 1: Reverse voltage across output rectifier diode D5,
5V/Div.
Reconfiguration Of The Evaluation
Board For 3.3V And 5V Dual
Outputs
The standard evaluation circuit can be easily reconfigured
into a 2A 3.3V and 0.6A 5.5V, dual output power supply. The
reconfiguration needs to populate the components for the
5.5V output rail, as shown in Figure 12. These components
are listed in the additional BOM list in the Appendix.
Reconfiguration Of The Evaluation
Board for Non-Isolated Output
Applications
For applications where output isolation is not required, the
non-isolated version of the evaluation board can be used to
(Continued)
FIGURE 11. Output Rectifier Reverse Voltage
Waveform
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reduce the BOM cost. Reconfiguration of the circuit board to
the non-isolated version can be accomplished in the follow-
ing four steps (refer to Figure 1 if not indicated otherwise):
1. Delete the unused parts from the circuit board as well as
2. Connect test points P5 and P6 with a bus wire of AWG
3. Short C28 pads by installing a 0Ω resistor of R2010 size,
4. Change C30 to 3.3 nF, C31 to 1.0 nF and R20 to 10 kΩ.
Figure 13 shows the schematic of non-isolated circuit for a
single 3.3V output. Similar changes also apply to the dual
output version.
Enhancing Input Filter
Performance
The evaluation board employs two 4.7 µF ceramic capaci-
tors (C4 and C5) as the input filter of the DC-DC converter
stage. The configuration is adequate to meet the IEEE
802.3af specifications, though it may be required to further
enhance the input filter performance for EMI / EMC consid-
erations. To do so, an inductor of 10 µH such as the Coilcraft
DO3308P-103MLD can be added. The inductor should be
installed in the L1 location on the top side of the PC Board,
a location originally shorted with a bus wire. Also, install a 22
µF aluminum electrolytic capacitor such as the Panasonic
EEV-HA2A220P in the C6 location right beside L1 on the top
side of the PC Board in order to protect the LM5072 IC by
absorbing the inductor energy during shutdown. A jumper
wire of AWG #28 or thicker with insulation sleeve should be
soldered to connect the junction of L1 / BR1 with the junction
of C6 / R27. By doing so, the 22 µF capacitor is placed in
front of L1 and directly across the VIN and RTN pins of the
LM5072. As a cost consideration, ceramic capacitor C5 (4.7
µF) can be deleted from the PCB, and L1 and C4 will be
adequate to attenuate the input ripple current below 2 mA
peak to peak .
the BOM: C20, C22, C25, C28, R7, R11, R16, R17, R24,
U2 and U3.
26 (refer to Figure 13).
or by soldering a piece of AWG 26 bus wire.
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