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LM5050-1-Q1: LM5050-1-Q1 Got damaged when power on

Part Number: LM5050-1-Q1
Other Parts Discussed in Thread: LM5050-1

Hi,friends,

I used 3 pcs of LM5050-1-Q1 to designn a Multi-battery charger.But it was alway got damaged when inserting the Battery .The TVS diode is OK.

Here are my BLOCK and SCH.Can you help me?

  • Hi Teddy,

    Can you let us know what is the damage you are seeing, type of damage?

    Also share the battery voltage and test conditions.

    Regards,

    Kari.

  • It's like voltage breakdown.When damaged,there is a 0.5V tube voltage drop between pin4 and pin1.And the D239 1N4148WT-7 melted,with no tube voltage drop between annode and cathode.

    The battery voltage is 53.5V and 53.6V,

    The test conditions:light load(about 30mA). When inserting the Battery,the LM5050-1 and 1n4148 got damaged.

  • I used 2 batteries with 2 LM5050,Both of them got damaged.

  • Hi 

    When battery is inserted to power LM5050-1, there is an inrush current through R1005 (100ohm 0402 package resistor), C394 (100nF) and D239 (100V rated, 130mA average current, 500mA maximum current rated diode).

    This inrush current is to charge the 100nF capacitor through 100ohms and the 1N4148 diode.

    Inrush through R1005, C394, D239 = (53.6V-0.6V) / 100ohm = 0.53A and this exceeds D239 1N4148 rating.

    Power dissipation on 100ohm resistor = 28.09W and this is huge for a 0402 package.

    Note that the 0402 packages are typically rated upto 50V.

    We recommend to chose R100 at be atleast 500ohm so that the peak inrush is limited to 0.106A and change the package of to 0603 or higher size.

    Recommend to change 1n4148 to higher current rated diode with 100V rating. 130mA average forward current rating of 1N4148 is not have acceptable margins.

    Regards,
    Kari.

  • Hi Kari,

    Thanks for your help!

    You have solved my problem.