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LMR36506-Q1: Output Voltage and Efficiency

Domenick DAmico
Prodigy 610 points
Part Number: LMR36506-Q1

Hello,

I am looking at the LMR36506-Q1 for an application targeting an output voltage of 24 V at 0.5 A max.  I've attached the Webench design here: 

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=4F9012D9EE5EDAFD 

I do have a few questions here.  Is this device capable of a 24 V output?  I believe so but I wanted to confirm as well since I couldn't find a specific range in the datasheet.  Also, there was a strange efficiency waveform on the Webench design attached below.  Is there a reason for this valley at 0.2 A on the efficiency curve?

  • 0
    TI__Expert 4301 points

    Hi Domenick,

      1. Yes, LMR36506-Q1 can support 24V output. I think the output is limited because of internal compensation, we'd better use it for 1~24V output application.

      2. I think it is caused by control mode switching between PFM(pulse frequency mode) and PWM. If we do not consider the control mode switching, we will get an efficiency curve that increases monotonically with the increase of load current.  Under light load current, PFM can achieve a higher efficiency than PWM.

      Refer to datasheet , we can see the integral efficiency curve. 0.2A load is near the critical point to enter PWM mode， so there might be a drop of efficiency.  In WEBENCH simulation, the current points are widely spaced, which also lead to the strange drop on 0.2A load.

    BR,

    Victor

      

  • 0 in reply to Victor Yu
    TI__Prodigy 610 points

    Hi Victor,

    Thanks for the quick response.  How do you mean the output is limited for internal compensation and using it for 1-24 V?

    I see what you are saying on the efficiency curve, so would this drop at 0.2 A be expected, or is there any way to improve that efficiency?

    Thanks again,


    Domenick D'Amico

  • 0 in reply to Domenick DAmico
    TI__Expert 4301 points

    Hi Domenick,

      1. I found a similar question answered by TI senior expert,please refer to the link below:

     https://e2e.ti.com/support/power-management/f/196/p/932717/3445674?tisearch=e2e-sitesearch&keymatch=LMR36506#3445674

      2. I think it is expected under the condition you set , but I didn't do a lab test to verify it. We may change the drop point by adjust inductance.

    BR,

    Victor