• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 518 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.

Original question:

LMR34206-Q1: Design

LMR34206-Q1: Operation Mode Performance

Ivan Liu Zhu
Prodigy 150 points
Part Number: LMR34206-Q1

Hi team, I have some questions regarding the operation of the LMR34206:

  • EMC Performance. There are 2 versions of LMR34206, one with FPWM and the other one has an auto mode for light loads. In general, which one of these 2 modes create less EMC emissions? Do you have a report with such comparison? I would like to understand if a fixed PWM signal generates more emissions or less emissions than PFM. 
  • Do you have a detailed graph/table where I can see when this buck converter switches between FPWM and normal PWM and also for the auto mode version between PFM and PWM?

Thanks.

  • 0
    TI__Mastermind 23685 points

    Hi Ivan,

    Please refer to the "Device Functional Modes (continued)" graph in the datasheet. The PFM mode is going to have worse ripple current at light loads which will have higher EMC emissions. Automotive customers who are worried about EMC emissions typically used fixed frequency devices and switch at 2.1MHz. 

    For your second inquiry FPWM means forced pulse width modulation mode. It is a factory setting programmed into the device. Typically it is used when constant frequency operation is more important than light load efficiency. It does not "switch" between FPWM and PWM modes. This device has a couple variants that are fixed at 2.1MHz.

    I don't have detailed information for this device, but here is a good general training video on how a device switches in and out of PFM mode:

    https://training.ti.com/introduction-buck-converters-understanding-mode-transitions

    Thanks,

    Andrew

  • 0 in reply to Andrew Kutzler
    TI__Mastermind 23685 points

    Hi Ivan,

    I haven't heard from you in a while.

    I'm going to assume this issue is resolved.

    Thanks,

    Andrew