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TPS62140 - About efficiency curve

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Guru 21045 points
Other Parts Discussed in Thread: TPS62140, TPS82130

Hi Team,

 

We would like to know about efficiency curve (Figure14 and Figure16 of datasheet).

What is the cause that efficiency falls to with the following points?


 

On the other hand, we can’t confirm this phenomenon in Figure14.

So, is this phenomenon affected by the switching frequency?

 


 

And, I have one more question.

Could you please let us know your efficiency measurement method?

 

Regards,

Kanemaru

  • 0
    TI__Guru**** 150950 points
    Efficiency is measured as it always is (and as is always has to be): (Vout * Iout) / (Vin * Iin).

    Does your application operate at that operating point (5Vin, 10 mA load)? There are better devices to use.

    If efficiency is important, then use the lower frequency selection. This gives much better efficiency,

    In light loads like this, we are in power save mode. There can be some jitter of the switching pulses at some points so that it makes it harder to correctly average out the input current to compute efficiency. Operation at this point looked perfectly fine.
  • 0 in reply to Chris Glaser
    Guru 21045 points

    Hi Chris-san,

     

    Thank you for your prompt reply.

    The maximum output current is around 1.5A.

    So, I understand that TPS62140 is suitable device.

    Our customer evaluated the efficiency of light loads at the following conditions.

     

    [TPS62140EVM conditions]

    -Vin=7.4V

    -Vout=1.2V

    -Iout=0mA to around 200mA

    -fsw=2.5MHz (The real frequency is around 1.7MHz)

    -L = 2.2uH (DCR=140mΩ(typ))

     

    However, the efficiency greatly decreases* at around 50mA.

    *efficiency of 7% worsens(76% at Iout=20mA => 69% at Iout=50mA).

    -71% at Iout=5mA

    -76% at Iout=20mA

    -69% at Iout=50mA

    -69.5% at Iout=100mA

    -71% at Iout=150mA

    -75% at Iout=200mA

     

    So, a drop of the efficiency is bigger than a result of datasheet.

    Will the efficiency decrease so much?

    I'd appreciate it if you could give me some advice about that.

     

    If you contact to below my e-mail address or let me know your e-mail address,

    I can send the customer information.

    I’m looking forward to hearing from you.

     

    [my e-mail address]

    Kanemaru-h@clv.macnica.co.jp

     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Guru**** 150950 points
    Thank you for posting your real question. Please don't ask theoretical questions like your first post when you have a real issue.

    Yes, your DCR is almost 10x higher than the inductor used in the D/S. This makes lower efficiency. As well, you can use the 1.25 MHz setting and get higher efficiency.

    This is a good device for your Vin and Iout needs. We also have the new TPS82130 module if a much smaller size is desired.
  • 0 in reply to Chris Glaser
    Guru 21045 points

    Hi Chris-san,

    Thank you for your kind support.

    I will report this infromation to our customer.

    Regards,

    Kanemaru