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TPS54160 EN pin current

Davide Ragazzi
Prodigy 20 points
Other Parts Discussed in Thread: TPS54160, TPS54260

hello,

i have a problem with TPS54160 EN pin.

In some devices  i have observed a different behavior with the same circuit interface (R1-R2 from page 14 of datasheet).

Input parameters:

VI = 5V

Vout = 3.3V

VSTART = 4,75V

VSTOP = 4,20V

R1 = 180K

R2 = 64,9K

The circuit works always correctly, but some devices have a VSTART higher than other so the output is not generated.

The En threshold has a large range and is variable with temperature..

But i watched that with decreasing value of resistence R1-R2 (in same ratio) the circuit is always activated.

There is a minimum current in input for EN pin?

There is a graphic more complete of VEN vs VIN and Temperature (fig 9 page 8)?

Thanks in advance

Davide

  • 0
    TI__Mastermind 35165 points

    Hi Davide,

    I do not have any of the info you requested available at the moment but I will let you know if I can dig some up.

    I believe the trouble your having is due to the variation in the EN voltage threshold.  On the data sheet it shows the EN threshold can be as high as 1.55V.  If you rearrange equation 3 to solve for VSTART with your resistances and the max EN voltage threshold your max VSTART is approximately 5.69V.  This is much higher than your VIN.

    I suggest designing with a lower EN threshold or design using the maximum EN threshold of 1.55V.  This changes your R2 to 88.7k. Let me know if changing this resistor works.

    Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 20 points

    Hi Anthony,

    thank you for reply.

    With your suggestion i'm sure that the circuit works, but in this way we have:

    with VEN (considered) = 1,25V

    VSTART = 3,62V

    VSTOP = 3.10V -> NOT OK FOR OUR PROJECT

    with VEN (considered) = 0.9V

    VSTART = 2.56V -> NOT OK FOR OUR PROJECT

    VSTOP = 2.04V -> NOT OK FOR OUR PROJECT

    In devices that don't work  (about 1% of production) we have measured I1 and IHys and we found:

    I1 = [0,76..0,84]uA

    IHys = [1,02..1,98]uA

    from datasheet:

    I1 = 0.9uA

    IHys = 2.9uA

    There is a possible problem of current variation?

    Is possible obtain VSTART and VSTOP request in my first post with this circuit or the variability of parameters is a large limitation?

    Thanks

    Davide

  • 0 in reply to Davide Ragazzi
    TI__Guru**** 191445 points

    As you point out there is also variation in the I1 and Ihys currents.  I should point out that the Vena wide distribution is over temperature and mostly at -40 C.  If you are not required to operate over that range, the Vena spec can be tighter.  Also, the pin compatible TPS54260 has a much tighter control over those parameters.  I believe the automotive catalog version of the TPS54160 has tighter tolerances as well.  Alternately, you could dispense with the external UVLo and use the internal UVLO.