LT8210 mode

Good morning. Good morning. To create a hold-up circuit for a load that accepts a power supply voltage from 18 to 32V, load at 60V a capacitor of 12mF and activating the EN/UVLO pin, I would like to use the lt8210 working as a buck until the capacitor voltage is reduced to 32V, take advantage of pass-thru operation up to 20V and then extract as much energy as possible from the energy stored in the capacitor by making the LT8210 work as a boost. I do not foresee current limitations, but given the current mode operation of the controller I have inserted 3 mOhm sensing resistors, with inductance of 4uH@10A & 5mOhm. Referring to the diagram of fig.16 of the data-sheet I connected 480k between Vout and FB1, 10k between FB1 and FB2, 10k between FB2 and Gnd. I also inserted 27k between Vc1 and Vc2. It escapes me, I did not understand, if the LT8210 manages the three modes of operation independently or if I have to insert a control circuit that acting on M1 & M2 imposes the required modes of operation, to obtine the function to maintaining the output voltage within 32->18V during the complete discharge of the capacitor.

Wthout it wasting time i cananticipate the problems of the LT8210, given the sad experience with other LT products.

Thank you for your attention

Best regards

Arturo Wolfsgruber

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  • +1
    •  Analog Employees 
    on Nov 25, 2020 2:10 AM 1 month ago

    Hi Arturo,

    The product expert responded to you by email. Here is summary of the recommendation:

    • See the attached worksheet with the circuit and component values. (not able to attach here to please check in email)
    • The MODE pins must both be tied to VDD. The MODE pins determine the operation. The LT8210 directly senses VIN and VOUT. The LT8210 automatically determines if it should be in buck, pass-thru, or boost based on their respective voltages. Page 18 of the datasheet goes into more detail on the operation. Additionally, attached is a model in LTSpice where I tried as best as possible to simulate your circuit. This simulation takes a while to run. There is also a demo board available for the LT8210 where you can experiment further to validate the performance you desire before committing to your own PCB design. Hopefully, this can improve your experience. 
Reply
  • +1
    •  Analog Employees 
    on Nov 25, 2020 2:10 AM 1 month ago

    Hi Arturo,

    The product expert responded to you by email. Here is summary of the recommendation:

    • See the attached worksheet with the circuit and component values. (not able to attach here to please check in email)
    • The MODE pins must both be tied to VDD. The MODE pins determine the operation. The LT8210 directly senses VIN and VOUT. The LT8210 automatically determines if it should be in buck, pass-thru, or boost based on their respective voltages. Page 18 of the datasheet goes into more detail on the operation. Additionally, attached is a model in LTSpice where I tried as best as possible to simulate your circuit. This simulation takes a while to run. There is also a demo board available for the LT8210 where you can experiment further to validate the performance you desire before committing to your own PCB design. Hopefully, this can improve your experience. 
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