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  1. #1
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    LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,
    I did experiment on LTC4015 IC for battery charging and discharging.

    As per datasheet typical application circuit, Verified Vin and battery charging and discharging. Its working fine.

    Above test i did with 3 terminal battery (positive, negative and NTC terminal)

    Battery has same over-current protection circuit for both charging and dischagring. (Because it has same path for both charge and discharge cycle)

    Charging and discharging has different current rating.

    So i chosen battery has separate charge and discharge path. (battery PMS circuit has separate over current protection circuit for both charge and discharge )

    For above 5 pin battery(charge positive, charge negative, discharge positive, discharge negative and NTC terminals), i have corrected LTC4015 circuit for separate charge and discharge path.

    Rocker switch is connected at J2.

    Please find the schematic diagram
    Click image for larger version. 

Name:	LTC4015 circuit for 5 pin battery.PNG 
Views:	11 
Size:	65.3 KB 
ID:	150561

    Issues :
    When turn ON and OFF the LTC4015 SYS teminal output(J2 connector), LTC4015 get damaged.

    Tested 2 boards, in both board after few events(5 to 10times of J2 switching) LTC 4015 failed.


    Observation :

    Observed that Both Q3 MOSFET top Gate terminal(TG) and LTC4015 SW terminal shorted with ground. (Q3 Top MOSFET Gate and source terminal shorted to ground)
    Removed Q3 MOSFET and verified that MOSFET not failed
    After Removing Q3, still short exist between SW terminal to Ground.

    Can you share me if you got any idea, Please share me.

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  2. #2
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,

    Sadly the schematic does not show what you are talking about.
    I must assume this is not your exact schematic.

    Pleae post your schematic.

    Did you follow all the datasheet recommendations regarding "absolute maximum ratings", capacitors and PCB layout?

    Klaus
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  3. #3
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Quote Originally Posted by KlausST View Post
    Hi,

    Sadly the schematic does not show what you are talking about.
    I must assume this is not your exact schematic.

    Pleae post your schematic.

    Did you follow all the datasheet recommendations regarding "absolute maximum ratings", capacitors and PCB layout?

    Klaus
    Hi Klaus,
    Thanks for response. Exact schematic only updated. can you say what are the point you are not getting clarity ?..

    Updated both schematics below,

    Schematic1 : (LTC4015 has same charge and discharge path)

    Click image for larger version. 

Name:	4015_Same charge and discharge path.PNG 
Views:	9 
Size:	90.3 KB 
ID:	150565

    Schematic2 : (LTC4015 has separate charge and discharge path)

    Click image for larger version. 

Name:	4015_Separate charge and discharge path.PNG 
Views:	5 
Size:	79.0 KB 
ID:	150566

    Schematic 1 verified completely. its working. same layout reference only followed for schematic 2and same components used.

    Schematic 2 changes is,

    U2 IC provided for discharge control and Q3 used for charge control. In schematic 1 both are sharing same path to battery. But we want to make separate path for charge and discharge. Hence i have separated the U2 IC drain terminal from R9 resistor and connecting directly to discharge terminal of battery. Q3 IC connecting to charge terminal of battery through R9 resistor.



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  4. #4
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,
    In Schematic 2, When connecting U2(OUTFET MOSFET) drain terminal to Inductor terminal and after removing C69, C70 capacitor, board is functioning properly. This circuit is same like schematic 1. I hope there is no issue with layout.

    I have a doubt about whether we can separate OUTFET MOSFET(U2) drain terminal from Inductor ?

    Can you please clarify on this ?

    - - - Updated - - -

    Hi,
    In Schematic 2, When connecting U2(OUTFET MOSFET) drain terminal to Inductor terminal and after removing C69, C70 capacitor, board is functioning properly. This circuit is same like schematic 1. I hope there is no issue with layout.

    I have a doubt about whether we can separate OUTFET MOSFET(U2) drain terminal from Inductor or not ?

    Can anyone please clarify on this ?



  5. #5
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,

    When turn ON and OFF the LTC4015 SYS teminal output(J2 connector), LTC4015 get damaged.
    1) I can't see how you turned ON/OFF LTC4015 SYS terminal.
    2) SYS is no output, it is an input.

    Show where and how you connected the rocker switch.

    Klaus
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  6. #6
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Quote Originally Posted by KlausST View Post
    Hi,


    1) I can't see how you turned ON/OFF LTC4015 SYS terminal.
    2) SYS is no output, it is an input.

    Show where and how you connected the rocker switch.

    Klaus
    Hi Klaus,
    Sorry for miscommunication, SYS terminal is the input voltage pin. Rocker switch is connected across J2 connector in Schematic. Switch not included in schematic. connected external to board.
    that is ON-OFF rocker switch.



  7. #7
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,

    I still donīt know hwo your description relates to the SYS terminal..

    Also I canīt whatīs the lowe node name of J2 and where it goes to because of bad picture quality.

    Please give all necessary details (pictures, descriptions and everything else) at once and unambiguous.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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  8. #8
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    Re: LTC 4015 IC gets failed when used for separate charge and discharge path

    Hi,
    In brief, my description is i want to use LTC4015 IC for separate charging and discharging path. From application circuit, to implement separate charge and discharge path i want to
    remove OUTFET drain terminal connection(U2) and connect it to battery discharge positive terminal. Sorry, I unable to insert PDF file.

    Just zoomed and inserted schematic file,
    Click image for larger version. 

Name:	LTC4015.PNG 
Views:	5 
Size:	72.2 KB 
ID:	150658

    J2 connector 1st terminal connected to LTC4015 circuit and 2nd terminal connected to our load. When turn ON rocker switch our load is connected to LTC4015 circuit.



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