• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 15 subscribers
  • Views 377 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.

ISOW7741: Efficiency drop-off at lower load currents

Matt Calvo
Genius 14745 points
Part Number: ISOW7741
Other Parts Discussed in Thread: ISO6441, LM5181, ISOW7841

Tool/software:

Hey Isolation Team,

I have a customer evaluating the ISOW7741 for a new project and it will be used in an application that will only be drawing around 5mA of load current through the device. Based on the efficiency graph (Figure 7-6 in the device DS) it looks like there is quite a steep drop-off in efficiency at load currents below 20mA.

Can this device tolerate and operate at loads around 5mA? Is there another device in your portfolio similar to the ISOW7741 that would be better suited for these lower load currents?

Best regards,

Matt Calvo

  • 0
    TI__Genius 17295 points

    Hello,

    Thanks for reaching out.

    Please allow me an additional 24 hours to reply.

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya V.
    TI__Genius 14745 points

    No worries at all Aaditya, thank you for the heads up. Looking forward to your reply!

    -Matt

  • 0 in reply to Matt Calvo
    TI__Genius 17295 points

    Hi Matt,

    I wanted to understand your questions a bit more. Are you asking if the ISOW7741 can support output load of 5mA with improved efficiency? or just 5mA generally?

    Regards,
    Aaditya V

  • +1
    Guru 316440 points

    This device will work correctly with any load current down to 0 mA.

    But the internal DC/DC converter is space constrained. If its efficiency is too low for you, then combine a plain isolator (e.g., ISO6441) with an external, isolated supply that is more efficient.

    When plugging the parameters into the Power Designer, it claims that the LM5181 with a 749196520 transformer can reach more than 80 % when supplying both the isolator and the load:

  • 0 in reply to Aaditya V.
    TI__Genius 14745 points

    Hi Aaditya,

    Happy to help clarify things; there are a couple questions baked into my original post but we are essentially wanting to confirm if the ISOW7741 is recommended to be used at load currents around 5mA in addition to asking if your team had any other device recommendations that would be better suited for this use-case.

    your feedback is very helpful; we really appreciate the design guidance and advice! :) 

    -Matt

  • +1 in reply to Matt Calvo
    TI__Genius 17295 points

    Hi Matt,

    Thanks for the clarification.

    As Clemens state in his post, the ISOW7741 can have a 5mA load. The ISOW7841 is also another Digital Isolators with Integrated DC/DC that we have available: ISOW7841 data sheet, product information and support. This device could be a possible option for you. The main difference between the ISOW7841 and ISOW7741 is the emissions performance. ISOW7741 has better emissions performance in comparison to ISOW7841 device.

    As Clemens stated, a general purpose Isolator device, such as the ISO6441, combined with an isolated supply is option to consider if efficiency is a concern

    Regards,
    Aaditya V