MPQ4263 Current-Limit feature

DC-DC Power Converters
1

Hello,

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I have replicated the referenced schematic using the MPQ4263GQVE-0002-AEC1 part number and am currently evaluating the current-limit functionality.

I have configured the current-limit feature based on the register settings specified in the MPQ4263 datasheet. As noted in the datasheet, the current-limit function is expected to operate only in Forced PWM mode. However, during testing, the expected current-limiting behavior is not observed in either Auto PWM or Forced PWM modes.

Test Setup and Configuration:
• VOUT set to 5 V with a DC electronic load connected
• Current-limit threshold configured to 0.7 A
• LDC disabled
• CC enabled, with CC blanking timer set to 3 ms
• Operating modes tested: Auto PWM and Forced PWM
• Sense resistor value: 5 mΩ

Observed Behavior:
• Load current exceeds the programmed current-limit threshold, indicating that CC mode may not be engaging
• The IMON pin remains at 0 V even when the load is drawing significant current

Could you please advise on the recommended next steps to debug or validate the current-limit functionality? Additionally, please let us know if there are any other configuration requirements, dependencies, or checks that we should verify.

Thank you for your support.

2

Hello @nuts1537 ,

Thank you for posting your question in the MPS Technical Forum.

Based on what you are describing in your test setup and configuration, you have followed the necessary steps to set the proper Current Limit.
First, just double check the value you selected for MFR_CURRENT_LIMIT register

Also, from what you described, this might be an issue with the sensing part of the circuit. The fact that IMON pin remains at 0V is telling us that there is no voltage drop across the sensing resistor (R4). Therefore, the internal comparator will always yield zero, thus the CC Current Limit Function will not operate.

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If you place a voltmeter across the sensing resistor, do you get any value reading?
Also, can you check if for register 0xD3 (MFR_CTRL3), bit 5 (RSENS), the selected sensing resistance matches.

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Regards,
Edgar