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TPS62825AEVM-126: 1.5V Efficiency

Robert Ortega
Prodigy 20 points
Part Number: TPS62825AEVM-126
Other Parts Discussed in Thread: TPS62825A,

Tool/software:

Hello,

I am measuring efficiency for a 1.5V design using the TPS62825AEVM-126 and I am calculating an efficiency of about 46% at a load of 30mA. According to the TPS62825A datasheet, the efficiency should be a little more than 90% (using figure 8-7, Vin = 3.3V Vout = 1.2V). Increasing the load current improves efficiency but it still does not align with figure 8-7. 

Below is what I measured.

Vin = 3.3V

Iin= 0.03A

Vout = 1.524

Iout = 0.03A

Below are the changes I've made to the evaluation board.

C6 = 10uF
C1 = 0.1uF
C5 = 10uF
R1 = 15.4k
R2 = 10K
C3 = 1200pF

  • +1
    TI__Intellectual 2770 points

    Hi Robert,

    The TPS6282xEVM-126 have TPS6282xA version of the device which is a FPWM version and always switches in FPWM mode. If you see the first plot on first page of datasheet you will see the two curves where the right side curves are for FPWM operation and left side are for the devices that operates in both modes until they connect the FPWM curve as shown:

    Even in figure 8-7 it is not mentioned that the curve is for F-PWM devices which means that it is for Auto version of devices. Instead you can refer to figure 8-9 in datasheet which is only for FPWM devices:

    You can estimate from this curve that for that much low current the efficiency of FPWM devices should be low.

    For high efficiency, at low loads, It is recommended to use Auto (PSM/PWM) devices as mentioned in the list in datasheet, shown below:

    If you are already using the Auto version of the device and seeing such low efficiency then let us know.

    Best Regards,

    Zakir

  • 0 in reply to Muhammad Zakir Baig
    Prodigy 20 points

    Thank you for the information. This clears things up.

  • 0 in reply to Robert Ortega
    TI__Intellectual 2770 points

    Hi Robert, Glad to hear that Slight smile

    Best Regards