LTC4020 choose components value

hi everyone,

i'm trying to use the Linear LTC4020 to charge a battery and use the load output

my features are

Input : 6-11V

Output : 11-13V (12v would be fine)

charge a LIFePO4 13.2V 2.5A battery

i'm puzzled in how to dimension the components in the right side of the schematic on page 37: all the features were right to just copy and paste that beside the battery chemistry is different

instead, on age 38, che chemistry is right but the voltages are different

also i don't know how to dimension he components on ITH pin(on the datasheet it suggests to use an analier which i don't have and refers to an application note which is different from the exact IC i'm using), VC and VFB pin, i'm no exactly sure if the values i calculated are correct for my battery

i need some help to calculate everything starting by my features

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  • 0
    •  Analog Employees 
    on Nov 30, 2020 9:58 PM

    I suggest starting from the DC2044A demonstration board schematic and layout.  I have attached a schematic with suggested modifications.  The DC2044A layout is also an excellent starting point for your layout.  Layout information is at https://www.analog.com/media/en/reference-design-documentation/design-integration-files/DC2044A.zip.

    PDF

  • hi ,

    after several months we got the bords and we are testing them and unfortunately, it doesn't work ...

    i have followed properly your suggestions but the STATUS1 LED is ON and nothing is oscillating

    I'm attaching the schematic i have made, and here is some explanations and measurements:
    I'm applying 12V at +V_IN_CHR and measuring output at +V_OUT_CHR
    in the output, i have of course the battery level passing by M408 but nothing else
    i have also 5V on +INT VCC and SHDN is 3.3V (more or less) so the device it should be ON

    i had also put VIN_REG to INT VCC to not use this function and also ILIM floating to not having any limits on the maximum currents. so all should be at the maximum capabilities.

    the rest is mostly what you suggested.
    as MOSFETs i had use AUIRFN8459 which i suppose they are not the problem here->
    www.infineon.com/.../Infineon-AUIRFN8459-DS-v02_01-EN.pdf

    what can it be?

    thanks for your time kind support

    EDIT:
    i did some more tests
    1_it doesn't work at 12V as i was in a need of, it works from 15V up (absorbing 11mA from the input)
    2_looks like the battery even with STAT1 led on, it charges VERY slowly, but i don't think it's really charging since measuring the MOSFET gates they are not really turning on and off, i see just noise

    what should i do ?

    PDF

Reply
  • hi ,

    after several months we got the bords and we are testing them and unfortunately, it doesn't work ...

    i have followed properly your suggestions but the STATUS1 LED is ON and nothing is oscillating

    I'm attaching the schematic i have made, and here is some explanations and measurements:
    I'm applying 12V at +V_IN_CHR and measuring output at +V_OUT_CHR
    in the output, i have of course the battery level passing by M408 but nothing else
    i have also 5V on +INT VCC and SHDN is 3.3V (more or less) so the device it should be ON

    i had also put VIN_REG to INT VCC to not use this function and also ILIM floating to not having any limits on the maximum currents. so all should be at the maximum capabilities.

    the rest is mostly what you suggested.
    as MOSFETs i had use AUIRFN8459 which i suppose they are not the problem here->
    www.infineon.com/.../Infineon-AUIRFN8459-DS-v02_01-EN.pdf

    what can it be?

    thanks for your time kind support

    EDIT:
    i did some more tests
    1_it doesn't work at 12V as i was in a need of, it works from 15V up (absorbing 11mA from the input)
    2_looks like the battery even with STAT1 led on, it charges VERY slowly, but i don't think it's really charging since measuring the MOSFET gates they are not really turning on and off, i see just noise

    what should i do ?

    PDF

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