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UCC14141-Q1: RLIM resistance value question

CHO SR
Genius 3415 points
Part Number: UCC14141-Q1

Hi,

The customer encountered an issue during the UCC14141 test.

It is confirmed that a fault occurs due to overcurrent at the output end and Retry is not possible with the output turned off.

The MCU is located in the high voltage region and is using UCC14141 output power.

When an overcurrent fault occurs, the MCU power is cut off, It is difficult to control Retry (ENA Toggle).

The customer wants to use the NC RLIM to see if there is any possibility of improvement.

Please recommend an appropriate resistance value that meets the conditions.

Voltage used: 8~18V / 1W : 18V / 55mA

If it doesn't improve, I think we need to add a reset IC.

  • 0
    TI__Mastermind 32775 points

    Cho,

    The RLIM is not used as what I believe you are describing. The RLIM is used to set the amount of source/sink compensating current used to balance the charge between a split capacitor output, when the UCC14141 is configured for dual output mode. the schematic you attached is single output mode and therefore RLIM is not used for the charge balance function. In single output mode, RLIM is only used to help discharge the output voltage during power down or fault conditions. Therefore RLIM is optional in the single output configuration. Also, if RLIM is used in single output configuration, it is recommended to connect it to VDD as you have it shown or it can be removed.

    The B1 and B2 ferrite beads should be ok but why are they there and what purpose do they serve? Also, the E-cap is not typically used here...try testing with it removed? Also, C24-25 are only rated for 25V with 18V working voltage applied. These caps are being used at nearly 75% their max DC voltage rating and I would expect that under these conditions their actual cap value is much less than 10uF each. If you can use caps rated for at least 35V (pref 50V), you can delete the E-cap. Pay close attention to the max power vs temperature derating curves. Below is for VDD-COM=18V.

    Regards,

    Steve