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Discontinuous Conduction Mode of TPS54360

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: TPS54360

I have a question about Discontinuous Conduction Mode of TPS54360. 

In datasheet p.32 "Discontinuous Conduction Mode and Eco-mode Boundary",

With an input voltage of 12 V, the power supply enters discontinuous conduction mode when the output current
is less than 300 mA.

I have a question.

When input voltage changes, does threshold current of  Discontinuous Conduction Mode change?

For example,

Vin is 30V, what is the threshold current that changes to Discontinuous Conduction Mode change?

Vin is 24V, what is the threshold current that changes to  Discontinuous Conduction Mode change?

Vin is 5V, what is the threshold current that changes to Discontinuous Conduction Mode change?

Best regards,

Takahiro Nishizawa

  • 0
    TI__Guru**** 191445 points
    Yes the DCM boundary changes with input voltage. But you cannot calculate it directly just from that. You have to know the output voltage, input voltage, switching frequency and inductor value. The DCM current threshold is given by:
    I(DCM) = ((Vout / Vin) * (Vin - Vout) / (Fsw * Lout)) / 2

    Also please remember that DCM boundary is not the same as eco-mode boundary. For TPS54360 you can be in DCM but not in eco-mode. See this app note for details:

    www.ti.com/.../slva388