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LM3485: LM3485MMX/NOP charging current abnormality

ELFIN JIANG
Prodigy 60 points
Part Number: LM3485

Hi Team,

When charging the LM3485MMX/NOP, the charging current is abnormal. We set it to 2.1A, but it can only reach 1.6A after power-on. After cross-verification, the bad phenomenon follows the material. What is the reason?

  • 0
    TI__Mastermind 35515 points

    您好，

    已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

  • 0
    Prodigy 60 points

    Hi Team,

    I would like to add a little more information. The power supply settings are: voltage 23.5V, current limit 2.1A. The current is 2.1A when the host is charging. The test is as shown on the right, which meets the current limit requirements. The abnormal host test current fluctuates between 1.5A and 17A. After replacing U1, it returns to normal. Replace the defective U1 with a normal PCBA, and the abnormality is reproduced. Cross-verification shows that the defective follows the host.

  • 0 回复 ELFIN JIANG
    TI__Mastermind 37870 points

    Hi 

    To check the calculation of R_ADJ and schematic review, please provide the following information.

    • What is the Vout_set? 
    • Please provide the complete schematic. [the connection from R11 is going to which point?]
    • what is the observed switching frequency?
    • What is the inductor peak current?
    • C6 (CFF) should be in parallel to top feedback resistor. Currently there is R7 [150kohms] in series with CFF. What is the purpose?

    • what is the purpose of this part?
    • Can you you reduce RADJ and check the limit?