Datasheet

Performance Characteristics

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10.2 Output Ripple Waveforms

Figure 4 shows the transient response for a load of change from 5A to 25A. The upper trace shows

minimal output voltage droop and overshoot during the sudden change in output current shown by the

lower trace.

Figure 5 shows typical output ripple seen directly across the output capacitor, for an input voltage of 48V

and a load of 30A. This waveform is typical of most loads and input voltages.

Figure 6 and Figure 7 show the drain voltage of Q1 with a 25A load. Figure 6 represents an input voltage

of 38V and Figure 7 represents an input voltage of 78V.

Figure 8 shows the gate voltages of the synchronous rectifiers. The drive from the main power transformer

is delayed slightly at turn-on by a resistor interacting with the gate capacitance. This provides improved

switching transitions for optimum efficiency. The difference in drive voltage is inherent in the topology and

varies with line voltage.

Conditions: Input Voltage = 48VDC Output Current = 5A to

Conditions: Input Voltage = 48VDC Output Current = 5A

25A Trace 1: Output Voltage Volts/div = 0.5V Trace 2:

Trace 1: Output Voltage Volts/div = 1V Horizontal Resolution

Output Current, Amps/div = 5A Horizontal Resolution =

= 1msec/div

1msec/div

Figure 3. Output Voltage Figure 4. Transient Response

Conditions: Input Voltage = 48VDC Output Current = 30A Conditions: Input Voltage = 38VDC Output Current = 25A

Bandwidth Limit = 25MHz Trace 1: Output Ripple Voltage Trace 1: Q1 drain voltage Volts/div = 20V Horizontal

Volts/div = 50mV Horizontal Resolution = 2µs/div Resolution = 1µs/div

Figure 5. Typical Output Ripple Figure 6. Drain Voltage of Q1

AN-1387 LM5026 Evaluation Board SNVA117A–September 2005–Revised May 2013

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