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TPS563209: Current Limit under VIN=5V, VOUT=1.2V, L1 = 2.2 µH

Motoyasu Hattori
Genius 9395 points
Part Number: TPS563209

Hi,

My customer wants to know the current limit value (Min/Typ/Max) under VIN=5V, VOUT = 1.2V , L1 = 2.2 µH.  According to the datasheet P.5, we can find the following under VIN=12V, VOUT=1.05V.  But there is no Vin=5V, Vout=1.2V data.

 

So could you please let us know how to calculate Current limit value on his condition?

Thanks and best regards,
M.HATTORI.

  • 0
    TI__Intellectual 1801 points

    Hi M.HATTORI,

    The OCL spec. in datasheet is actually the valley value, so the typical output current limit value can be calculated with: I_limit=4.2+Ip-p/2

    In this case, VIN=5V, VOUT = 1.2V , L1 = 2.2 µH, then Ip_p/2=0.13A, so I_limit= 4.33A.

    You can also use this method to calculate Min/Max value.

    Regards.

    Jared

      

  • 0 in reply to Jiandong Liu
    TI__Genius 9395 points

    Jared-san,

    Thank you for your reply, but I am confusing.

    In general, when current limit is detected on Valley Value timing by comparator, current limit is constant and independent of L. On the other hands, Icol is depend of L on the datasheet P.5.

    Could you please let us know where current does comparator observe?   Please advise us.

    Thanks and best regards,
    M.HATTORI.

  • 0 in reply to Motoyasu Hattori
    TI__Intellectual 1801 points

    Hi M.HATTORI.

    Your understanding are right, the valley value of current limit is constant, independent of L. 

    For TPS563209, the valley current limit is constant: I_limit_valley=4.2 A. In datasheet Page.5, the L and output voltage information are actually useless or should not be there.   

    And due to the output current is the average of inductor current, so the output current limit: I_limit_ouput= I_limit_valley + Ip-p/2;

    where, Ip-p/2=

    Regards,

    Jared.