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PMIC - TPS65217D efficiency

Harsha Lalwani
Intellectual 315 points
Other Parts Discussed in Thread: TPS65217

Hi all,

We are using TPS65217D PMIC in our design.

We wanted to know the efficiency of the internal DCDC converters. 
From our side, we calculated the efficiency by measuring the input and output power of the PMIC. We found that it is somewhere near to 75%.
We are unable to find the efficiency details in the datasheet. 

Please share any links where we can get the efficiency details.

Thanks
Harsha

  • 0
    TI__Genius 10885 points

    Hi Harsha,

    Section 8.6, Figure 2 of the TPS65217 datasheet shows typical efficiency curves for the DCDCs. Please also remember that the particular inductor, input and output voltage level, and source pin will also impact efficiency.

    For instance, using the AC pin as the supply will have slightly lower efficiency than if one were to use the BAT pin, as the AC-to-SYS path requires an internal load switch with approximately 150mΩ RDson, whereas the BAT-to-SYS path does not. This may have an impact on your measurements.

  • 0 in reply to Richard Solarski
    Intellectual 315 points

    Hi Richard,

    Thanks for the reply.

    I have gone through the TPS65217 datasheet, section 8.2, Figure 2. The curves detailed in the figure 2 are with respect to the 5V.


    In our case, we are using a battery connected to BAT pin of PMIC with a voltage of 3.7V. With battery as input supply and 3.7V as input voltage, we have measured the output currents from VDCDC1 and VDCDC3 of PMIC.

    VDCDC1 - 117mA
    VDCDC3 - 130mA

    Using these values, we calculated the efficiency and we found the efficiency of both DCDC converters to be around 75%.
    Also, the inductor used in our design is same as the one which is mentioned in the datasheet (LQM2HPN2R2MG0L).
    Is 75% efficiency is expected wrt the mentioned current and battery voltage ?


    Please suggest.

    Thanks
    Harsha

  • 0 in reply to Harsha Lalwani
    TI__Genius 10885 points
    Hi Harsha,

    I would expect it to be higher than 75%, somewhere above 80%, as I'm assuming you are around 1V and 1.1V out, in PFM mode. Were your input and output voltage measurements on the input and output caps? If not, recollecting this data at these points can help us understand if board layout is decreasing your performance. Is this on a custom board or EVM?
  • 0 in reply to Richard Solarski
    Intellectual 315 points
    Hi Richard,

    Sorry for the late reply.

    In my last post, I missed out to mention the voltages.

    VDCDC1 - 117mA - 1.35V
    VDCDC3 - 130mA - 1.12V

    As per your suggestion, we measured the voltages at the input and output decaps of PMIC.
    With this, we found that efficiency is near to 82%.
    There was slight variation in the voltages at source generation point (PMIC output) and the points where we measured earlier. And because of which we were seeing the dip in the efficiency.

    We are measuring efficiency on the custom board.

    Thanks for your support.

    Regards
    Harsha