• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 62 subscribers
  • Views 533 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LM5085 feedback resistance issue

Hsin-Hua Tseng
Prodigy 50 points
Other Parts Discussed in Thread: LM5085, LMP8646, LM25085

I have read the datasheet of LM5085 (SNV565G).

(1)  This document suggests me that RFB1 and RFB2 should be chosen from 1KOHM to 20KOHM (page 15). But in my application, the output voltage will be 58.4V. It will means that the current leakage is about 2-4mA in feedback path. According to this document, the bias current of the feedback pin is only 10nA. Can I choose RFB1 and RFB2 with high value (i.e. 300K or higer) to reduce power loss?

(2) Can I use a current sense IC (like LMP8646) or similiar circuit to sense output current and loop back to FB pin of LM5085 directly to limit the max. output current and create a CV/CC lithium battery charger?

Thanks

  • 0
    TI__Genius 11490 points

    Hi Tseng,

    The characterisation of the IC is done with the values recommended in the datasheet.You can use higher values with the caveat that the bias current will produce error with higher values. Also any other leakage current becomes important.

    It is possible to use a current sense amp to create a CV/CC characteristics. There is an app note in the LM25085 folder that shows how to do it wihtout a current sense amp but I think the current sense amp approach is likely to be cleaner.

    Thanks and regards,