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TPS63070: Maximum Duty Ratio

Ryu Yamashita
Genius 4145 points
Part Number: TPS63070


Tool/software:

Hi team,

The PS pin is dropped to Lo and the switching frequency fs is set to fixed (2.4MHz) to output 5V.
I thought it would always be 2.4MHz, but when the potential difference between input and output is less than 0.8V, it becomes 1.2MHz.
I assumed that this was due to a limit on the maximum duty ratio or potential difference, is this correct?
And if so, I would like to know the specific value.

Best Regards,
Ryu.

  • 0
    TI__Genius 17680 points

    Hi Ryu,

    Thank you for reaching out. I am not sure about your working condition. Can you provide Vin, Vout, Iout information? Do you have a schematic? Can you provide waveform of SW1, SW2, Vin, Vout, inductor current?

    Regards,

    Mulin

  • 0 in reply to Mulin Yuan
    Genius 4145 points

    Hi Mulin,

    The output voltage of the IC is set to 5V
    VIN 346mA at 6V (switching frequency 2.5MHz)
    VIN 356mA at 5.3V (switching frequency 1.25MHz)

    The schematic is almost the same as the Simplified Schematic in the datasheet.
    0.1μF is added to CIN and COUT.

    Waveforms are attached.

    Best Regards,
    Ryu.

  • 0 in reply to Ryu Yamashita
    TI__Genius 17680 points

    Hi Ryu,

    I will look into this and reply to you later.

    Regards,

    Mulin

  • +1 in reply to Ryu Yamashita
    TI__Genius 17680 points

    Hi Ryu,

    Thank you for your waiting. 

    Vin=6V, Vout=5V, TPS63070 works in buck mode, only buck side MOS switch, frequency is 2.5MHz。

    Vin=5.3V, Vout-5V, TPS63070 works in buck-boost mode, which is one cycle buck and one cycle boost. So both LX1 and LX2 switch, the frequency will reduce to half for LX2 and LX2. But this is IC normal behavior.

    Regards,

    Mulin