• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 466 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC28881EVM-680: Making a battery charging circuit with UCC28881EVM-680

Ayan Moni
Prodigy 20 points
Part Number: UCC28881EVM-680
Other Parts Discussed in Thread: UCC28881, UCC28704, BQ24401

We are trying to use the UCC28881 to charge a nickel cadmium battery. The input power should not exceed 0.8 W and we are eyeing 80% efficiency. The max battery voltage is 7.5 V. What should be the chnages made in the existing circuit for the EVM to operate it at a constant current mode?

  • 0
    TI__Intellectual 880 points
    Hey Ayan,

    The UCC28881 does not have a constant current mode. The UCC28881 does feature current limiting and current runaway protections, however. You may be able to get the UCC28881 to regulate current by using a shunt resistor to represent your current as a voltage, but then the output voltage of the system is now not regulated, meaning it can fly anywhere to get the right output current.

    If you are looking for a constant current, constant voltage controller I would recommend the UCC28704 since it is has constant current under voltage protection feature. This feature is explained in more detail in section 7.3.8 in the device datasheet (www.ti.com/.../ucc28704.pdf).

    But for a specific nickel cadmium battery charger, I would recommend taking a look at the BQ24401 which is a programmable battery charger specifically made for handling Nickel Cadmium safely with several charging termination criteria.

    Regards,
    Davit
  • 0 in reply to DavitKhudaverdyan
    Prodigy 20 points
    Hey Davit,

    Thanks for your reply. I am going through the suggested converters to see if it matches our requirement. In the mean time i have one more question about UCC28881. The output voltage is constant at 13 V in loaded condition. Can we change this to any other value like 12V or 11V based on our requirement?
  • 0 in reply to Ayan Moni
    TI__Intellectual 880 points
    Hey Ayan,

    Glad to be of help!

    You can change the output of the UCC28881 EVM by modifying the feedback network. Modifying the feedback network also means you will have to make changes to the pre-load resistor. Sections 9.2.1.2.5 and 9.2.1.2.7 go over the pre-load resistor and feedback network in detail, respectively.

    Link to datasheet: www.ti.com/.../ucc28881.pdf

    Regards,
    Davit