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TPS62A01: PSM vs. PFM noise comparizon

FINN NIELSEN
Prodigy 10 points
Part Number: TPS62A01
Other Parts Discussed in Thread: TPS62060,

Tool/software:

We are designing a battery operated sensor interface that must not cause magnetic field, due to high peak currents in the sub 5Khz range, as this is the nearby sensors detection range.

Sensor consumes less than 3mA in idle mode, but as it is wireless it regularly kicks in a radio, consuming 500-800mA.

High efficiency in the 90% range is essential. 

We are looking at TI regulators with both PSM (Pulse Skip Mode)=TPS62A01 and PFM (Pulse Frequency Mode)=TPS62060 

Our concern is that low power mode could cause switcing currents with repetition frequency close to 5Khz or below, when operating under 3mA.

We are also concerned about high current peaks at low power to high power changover.

Which low power technology (PSM/PFM) minimizes the peak currents in the two cases most?

  • 0
    TI__Expert 4520 points

    Hi Finn,

    Thanks for using E2E.

    I would like to clarify some acronym:

    • PSM = Power Save Mode
    • PFM = Pulse Frequency modulation
    • PWM = Pulse Width Modulation

    Both devices have a Power Save Mode were the control logic switching from PWM to PFM at light load to have better efficiency.

    Could you please provide the conditions for your application to check the frequency behavior for the two devices:

    • VIN
    • VOUT
    • Temperature range

    Best regards,
    Sepp

  • 0 in reply to Josef Marsmann
    Prodigy 10 points

    Hi Sepp,

    So, The power saving modes are the same of the two devices. Looking at the PSM/PFM scope plots in datasheets it seemed that TPS62A01 generates a series of pulses with the fixed frequency interval where TPS62060 generates one pulse and repeats this with an interval determined of the voltage achieved; hence these Power Save Modes seemed different and I assumed this was why TPS62A01 documentation does not refer to PFM, but looking at the 8.4.2 description of TPS62060 power modes I can see that PFM can generate subsequent pulses and thereby do the same as for TPS62A01. Thereby clarified regarding the non existing difference in the Power Save Modes.

    Then remains the difference in how they react on change from Power Safe Mode to PWM mode. TPS62060 datasheet displays an undesired current peak upon entering PWM mode (figure 18), where the TPS62A01 does not have any such depiction giving a hint of the performance in that conjunction. We would rather have a bigger dip in output voltage than have the current peak. Is there more performance data available for the TPS62A01?

  • 0 in reply to FINN NIELSEN
    TI__Expert 4520 points

    Hi Finn,

    Could you please provide the conditions for your application to check the load transient behavior for the two devices:

    • VIN
    • VOUT

    Best regards,
    Sepp