Tool/software:
Hi team,
Could you tell me about my colleague Go’s question from the other day?
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My custumor is designing a circuit to convert DC 24V to 3.3V using the LMR51430XFDDCR.
My customer has an input voltage range of (18Vmin to 24Vtyp to 31.2Vmax). Under the following conditions, they observed the switching waveform and confirmed a frequency foldback phenomenon (500KHz to 250KHz):
- Conditions: Input voltage: 31.2V, Output voltage: 3.3V, Output current: 3A
The inductor current (light blue) and the switching waveform of pin 2 (light blue) of the LMR51430XFDDCR are as follows.
Vin:31.2V Vout:3.3V Iout:3.0A
Vin:31.2V Vout:3.3V Iout:2.5A
The output current value at which the frequency starts to fold back changes depending on the Vin value. This relationship is shown in the table below.
The left column shows Vin (V), and the right column shows the point where the frequency starts to change.
From the switching waveform, it seems that ton_min and ton_max, where the frequency folds back, are not addressed.
Additionally, I don’t think it falls into light load mode based on the load current. There are other concerns such as heat generation, but what could be the cause of the frequency foldback?
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Best regards,
Kyohei
