• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 376 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.

CSD87350Q5D: OCP limits

Michael T Schneider
Expert 3790 points
Part Number: CSD87350Q5D
Other Parts Discussed in Thread: LM27403

Hello team,

We are using the CSD87350 in a POL application along with the LM27403 controller. We need to characterize the resistance the half-bridge has between the TGR sense point and the SW node.

We are implementing Inductor DCR sense for over-current protection and have tied one side of our sense network to the TGR node and the other to the inductor output per an app note in the LM27403 datasheet. Lab measurements are giving us OCP limits that suggest an extra 500uOhms. Is this accurate? Do you have any data on this – perhaps over temperature?

Thanks for your support!

-mike

  • 0
    TI__Mastermind 38130 points
    Hi Mike,
    This is a great question. Let me check with the team to see if we have more information. The resistance between VSW and TGR is mostly due to the copper clip is not specified in the datasheet. The resistance will have the temperature coefficient of copper. I will update when I have more information.
  • 0 in reply to John Wallace1
    TI__Mastermind 38130 points
    Hi Mike,
    The recommendation in the LM27403 User Guide (Literature Number: SNVU330), tries to take advantage the power block clip resistance to produce a higher magnitude current sense signal. The feedback I've gotten is as follows: It is ~0.4 to 0.5mOhm for CSD87350. Using TGR as the sensing point for DCR is the wrong approach. It should be sensed at the VSW pad of the output inductor. Using the clip resistance makes the DCR tolerance really bad and it varies with different PCB layout and different FET packages, and it is difficult to compensate for temperature. As mentioned previously, the clip resistance is not specified in the datasheet and therefore TI cannot guarantee a value or range of values.