Other Parts Discussed in Thread: LM5180,
Hi, team,
A customer is checking LM5180 operation and has some questions. Please refer to the attached document first.
The attachment shows,
Measured SW terminal voltage and transformer primary current waveform when 100mA(15v) & -150mA(-7.7v) load are applied to two outputs under VIN = 5V using LM5180EVM-DUAL. At this time, the primary winding current of the transformer is measured at the two measurement points shown in the document and has a different waveform.
In the above measurement results, there are the following questions.
Q1: In this measurement, each output voltage dropped to 13.75V & -6.853V below the set value (15v & -7.7v). This should have been probably caused by the LM5180 reaching its current limit. Is this understanding correct?
If the output voltage drop occurs because the LM5180 has reached the current limit, the current waveforms at measurement points -1 and -2 are different, and the current waveform at measurement point -2 (peak value = 1.74A on the wabeform) is closer to current limit value (spec: min1.35A/TYP1.5A/MAX1.65A) of LM5180 SW pin.
Q2: Is it okay to understand that the waveform at this measurement point-2 represents the actual SW pin current of the IC?
Q3: Why is the waveform at measurement point-1 like this? (What are the factors that cause this difference in current waveform at the two measurement points?
Regards,
