LTC7862 can't be started with load, but it can be loaded after no-load start.

Dear engineer,

      LTC7862 can't be started with load, but it can be loaded after no-load start.The schematic is as follows(The schematic is a reference chip manual)

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  • +1
    •  Analog Employees 
    on Jul 23, 2019 4:16 PM over 1 year ago

    Hi

    I noticed that R6b resistor that is connected to VIN pin of the LTC7862, its value is too large.  I would suggest using 2.2 ohm with the case size of 1206 instead of 2.2Kohm.  See schematic attached with R6b resistor indicated by a red circle.  This is the cause of the startup problem since VIN can't supply enough current to DRVCC pin during soft-start switching mode.

    I also noticed that DRVUV pin must be connected to INTVCC pin with a zero ohm resistor with the FETs that you used for this design.  Do NOT populate and remove the zero ohm resistor from DRVUV pin to GND.

  • Thanks for your answer!I have changed the resistor, the fault phenomenon have disappeared.but another fault phenomenon that pin of TG and SW will short happened occasionally when the current of the load increases
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