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LT8210 Burn out the mosfet

Category: Software
Product Number: lt8210

Dear ADI:

    I use lt8210 for buck boost charger for battery , But now I use 2.5mΩ RSENSE series to inductor for sample inductor current , And my inductor saturation current about 30A , When input is 39V, output is 54.7V, LT8210 work in boost state and CCM mode ,Then the MOSFET A  and C  is burn out , Maybe Overcurrent  and inductor saturation, But i Check the datasheet page 5 about "Cycle-by-Cycle Inductor Current Limiting" ,The give message is that "VSNSP1 – VSNSN1 = 50mV"  If 50mV is correct , When I use 2.5mΩ Rsense , The Maximum current  just only 20A , I wanna know the VSNSP1 – VSNSN1= 50mV is right or not ,TKS!

  • Hello fhlxUpdate,

    My name is Chris Gass. I am the factory application engineer supporting the LT8210. Yes, the VSNSP1-VSNSN1 threshold is 50 mV.

    Please let me know if you have further questions,

    Chris

  • Dear Chris: Now i have Fixed startup issues, But now i have find the problem as following:

          I use 4 mosfet, Every mosfet Qg about 50nC Then operation frequency is 200Khz, So i count out the current comsumption 

    I = 4*50nc*200K = 40mA, And external power 13V supply to EXTVCC and GATVCC about 10V ,When output current less than 0.5A/50.4V, GATVCC Ripple is very good, And LTC8210 efficient arrivate at 98.5% in CC mode, But if increase output current, For example 1A ,The lt8210's  GATVCC is very unstabity, So many problem is out, can you help me find out the reason

        I use external Switch Power IC power to EXTVCC pin ,can output 1A, When GATVCC unstabity, EXTVCC pin signal is very stablity

  • Dear Chris:

        First burn out mosfet and LT8210 Chips, Mainly problem is GATVCC is untabilty, If load over 0.5-0.6A , GATVCC output voltage is unstable and the SW1 and SW2 ringing is very serious like a wave, I try to add capacitor to GATVCC pins from 10uF to 20uF, Never change the impact,Maybe GATVCC Insufficient driving ability To 40mA, Or other problem, Or VC loop compensation ????

  • Hi fhlxUpdate,

    This sounds like the capacitor on either GateVCC or EXTVCC is to small. Try increasing the size of the capacitor.

  • hi cgass:

        Anther problem is that, The Internal GATVCC fault occured is easy ,For debug the board , I have used various MOSFET, But some mosfet cause the GATVCC output just 5V, Maybe it has some error, By the way, Can we short the ExtVcc and GATVCC?????

  •          Another problem when some chips GATVCC LDO have fault, Just output 3V to 5V,  No way for me, Cux ,All of sample chips have error, I just short GATVCC and EXTVCC, Strange phenomenon happened, boost and buck  is all work fine, But output voltage deviation about 3-5V, As the input gets higher and higher, the output deviates more and more! I can't understand the appearance,  The experience just as a test session,  But my mainly problem is how to protect GATVCC, If it's always have error when work with various Mosfet, Anyone have same prolblem with me ?

  • Hi fhlxUpdate,

    These are all new problems. I get very few questions on this part as it usually just works. Can you send your schematic and PCB layout? Gerber is fine.

    Did you get a demoboard and validate performance? It is good to have a demoboard as it is a reference you can compare.

    Thank you,

    Chris

  • Top layout

    inner for GND

    Inner for sigal

    bottom layout

    component and Top layer

  • PDF

    This sheet come from ADI Demo board 

  • Hi fhlxUpdate,

    The layout I think is OK. 

    I look at your schematic. You have a GATEVCC cap of 10uF and boost caps of 0.47 uF. Please check these values. If the ratio of GATEVCC cap to boost cap is not very high, then you can have difficulty getting a good GATEVCC voltage. As a rule of thumb, the GATEVCC cap should be 100x the boost cap. Please check to make sure that you have adequate GATEVCC capacitance.

    Thank you,

    Chris