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TPSM843820: Design tool for WEBENCH or CALC-TOOL-TPSM843X20

Masashi Mineda
Expert 1315 points
Part Number: TPSM843820
Other Parts Discussed in Thread: TPSM843A22,

Tool/software:

Dear Sirs and Madams,

We would like to know about inductance when considering current limiting and inductor ripple current.

Our operating conditions are as follows:

Vin: 5V

Vout: 1.8V

Fsw: 1MHz

WEBENCH does not generate any errors under these conditions.

However using CALC-TOOL-TPSM843X20, a warning or caution will be issued regarding inductor ripple current.  

Our application does not allow switching frequencies above 1MHz.

This module uses a 220nH inductor, so the inductor ripple current is calculated to be approximately 5.2A (= approximately 65% ​​of the output current).

Naturally, I understand that inductor ripple current affects ⊿Vout, current limit, and responsiveness.

Is it possible to set the switching frequency to 1MHz and use it with an input voltage 5V and an output voltage 1.8V?

Regards,

Masashi

  • +1
    TI__Mastermind 25130 points

    Masashi-san,

    The operation at 5V to 1.8V at 1MHz will depend on the minimum and maximum load. 

    At 0A, the sinking current limit when including Ltol will exceed the sinking current limit threshold causing a nonperiodic switching.  

    Similarly,  at 8A, the sourcing current limit will be exceeded and the output voltage will droop. 

    The TPSM843A22 may be an alternative to consider.

    Regards, 

    David

  • 0 in reply to David_Daniels
    Expert 1315 points

    Hello David,

    Thank you for your advice.

    Our application has a height limit of 2.0 mm and a maximum operating frequency of 1 MHz.

    This makes it difficult to use the TPSM843A22.

    We understand that a negative effect of a higher inductor ripple current is that the output ripple voltage increases, but because light load and maximum load conditions will not be encountered in this case, it looks like I will end up using the TPSM843820.

    Regards,

    Masashi