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TPS2662: Fault indicate problem for TPS26601

Satoshi
Guru 19645 points
Part Number: TPS2662
Other Parts Discussed in Thread: LM2622, LP2951, TPS7A3401, TPS1663, TPS1653

Although TPS26601 operate 5Vin and 63mA, /FLT pin output is asserted.

I referred below application note and add current limiting resistor: 3kΩ, but /FLT assert was not disappear.

(Blocking diode can not add because of board size)

https://www.ti.com/jp/lit/an/slva934a/slva934a.pdf

I guess that above problem have the other reason.

My question is two points below;

①Please let me know about possibility to reason and idea for measure.

②Is current limiting resistor value based on Vin, correct?

　If Vin is differ from VIO voltage (ex. Vin: 5V and VIO: 3.3V), which based voltage correct? 

【Circuit information】

・Vin and Vout: 5V

・The other external value is attached below;

TPS26601 - Design Calculator Rev1p0.xlsx

・/FLT output is connect to CPU input, 3.3V with 10kΩ pullup.

Best regards,

Satoshi

  • 0
    TI__Guru** 105661 points

    Hi Satoshi,

    FLT/ assertion might be due to reverse current fault trigger.

    Few questions: In your test waveform, why there is a jump in Vout ?

    what is the load type?

    Is Vin at 5V ?

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 19645 points

    Hi Rakesh

    Thank you for reply,

    ・Load (output) side is connecting Boost DC/DC: LM2622, 5Vin ⇒11.5Vout.

    ・Sorry, blue waveform is unrelated, Vin is 5V.  

    ・The reason for Vout jump is confirm and feedback later.

    Please let me know if you have any notice.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru** 105661 points

    Hi Satoshi,

    since Vout has jumped and created a situation of Vout>Vin, reverse current fault might have triggered.

    Is this issue happening only at light load ? or at higher loads also such as 1A, 2A etc ?

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 19645 points

    Hi Rakesh

    Thank you for advice.

    This issue happen only light load, 1A and over are not happened.

    I attached power block diagram.

    LM2622 is always enable: ON, timing for this issue happen is Enable: OFF → ON for TPS7A3401 and LP2951 ×2.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru** 105661 points

    Hi Satoshi,

    The switching noise of the load might be affecting the eFuse operation and triggering reverse current fault. Can you increase output capacitance of the eFuse and check the behavior.

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    Guru 19645 points

    Hi Rakesh

    Thank you for advice,

    Zoomed waveform is attached below; 

    ・Cout: 47μF, Vout_min: 4.66V ~ Vout_max: 5.56V

    ・Cout: 47μF ×4, Vout_min: 4.66V ~ Vout_max: 5.31V

    I continue to request the test for much more Cout value.

    I'll feedback to you later.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru** 105661 points

    Sure Satoshi.

    Can you also check the reason for the dip in the Vout.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Guru 19645 points

    Hi Rakesh,

    Please see additional information below;

    ・When output capacitance increase 47μF ×8, but Vout jump have not reach Vout>Vin +10mV.

    　And customer can't add more capacitance value because of board size limitation.

    　※Cout: 47μF ×8, Vout_min: 4.717V ~ Vout_max: 5.262V

     ・Now Vout dip is confirming, by the way inrush current is not find around TPS26602 and TPS2622.

    Please let me know additional question below;

    ・I guess that improve point for voltage jump and dip is TPS2622 and LDO's because of TPS26602's board size.

    　Is there way to idea for improve? (For example, increase capacitance, etc) 

    ・If replace TPS26602 to TPS26601, is there possibility to more abnormal operation?

    　I expect that /FLT high to low, and not return to high.

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Guru** 105661 points

    Hi Satoshi,

    The issue remains even if we replace TPS26602 with TPS26601

    One option to solve the issue with out increasing the output capacitance is using devices like TPS1653, TPS1663. These devices does not has reverse current protection and are ideal for your application.

    Best Regards,

    Rakesh