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TPS54160 EN pin problem - generated design exceeds datasheet specifications

Johnny Roberts
Intellectual 350 points
Other Parts Discussed in Thread: TPS54160, TPS54231

The TPS54160 includes an Enable pin which is commonly fed by a resistor divider from the supply input to enable under/over voltage lockout.  SwitherPro's calculated resistor values exceed the datasheet specifications for this pin.  This is reproducible:

1. Select new design using TPS54160

2. Select in voltage of 30V and 36V min and max, respectively.

3. Select output voltage of 5V and current of 1.5A.

The suggested resistor divider values for the Enable pin are 348k and 78.7k.  At the minimum input voltage of 30V the enable pin voltage would be:

30V (78.7k) / (78.7k + 348k) = 5.53V.

Per the datasheet, the EN pin absolute maximum is 5V.

  • 0
    TI__Intellectual 2710 points

    Hello,

    We are working on this issue currently. The fix will release in a few weeks.

    Thanks,

    Hetal.

  • 0 in reply to Hetal
    Prodigy 40 points

    I'm finding a similar problem with the TPS54231.  The EN resistor divider values from the Tool seems way off and totally inconsistent with calculating the values by hand from the equations.

     

  • 0 in reply to Burt Hashizume
    TI__Expert 3875 points

    Hi Burt,

    The original post (from Dec 14, 2009) was about the TPS54160. That problem has been fixed.

    I cannot reproduce this problem on the TPS54231. All my SwitcherPro TPS54231 designs get R6=348kOhm and R7=71.5kOhm. An example is shown below:

    In the worst case, when VIN is at 30V (max allowed in page 2 of data sheet), the EN pin will be at ~5.3V, which is less than the allowed maximum of 6V:

    If you can produce a design where the EN pin exceeds 6V, could you please post it.

     

    I did find a different (but related problem) with the TPS54231. For the TPS54231, R6 and R7 don't change. So UVLO start is always ~7V and UVLO stop is always ~6V. This creates a problems for a design like this, which is intended to work down to 4V:

    Is this the problem that you are referring to? I will ask the developers to re-validate their code for calculating R6 and R7 to address this issue.

    Regards,
    Michael
     

    -- 
    Michael Krasnicki
    Analog eLab
    Texas Instruments