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TPS7B68-Q1: TPS7B6850Q-Q1 V(PGADJ_TH) and PG threshold for Vout rising and falling

Toshio Ushikubo
Mastermind 9620 points
Part Number: TPS7B68-Q1

Hello,

 

Please answer following question from customer.

 

Q1: V(PGADJ_TH)

Please advise, if following V(PGADJ_TH) min, typ and max voltage will change linked to Vout voltage or these values are constant in spite of Vout is 4.9V(-2% of 5V).

If V(PGADJ_TH) min and max voltage change linked to Vout voltage, please advise how to calculate min and max voltage when Vout is 4.9V and 5.1V.

 

 

 

Q2: V(PGADJ_TH) accuracy

Datasheet 7 describe V(PGADJ_TH) is 1.067V(min), 1.1V(typ) and 1.133V(max) and it is 1.1V +/- 3%.

But datasheet page 13 describes as follows.

 

Please confirm that V(PGADJ_TH) accuracy is +/-3% or +/-2%.

 

 

 

Q3: Vout threshold when PG turns high and low

I want to confirm my understanding of turn on and off Vout threshold when using Adjustable Power-Good Threshold.

 

Q3-1: V(PG_ADJ)max

Is it correct that V(PG_ADJ) max that is Vout highest threshold of PG turn high is calculated as follows?

 

Q3-2: V(PG_ADJ,LOW)min

Please advise which equation is correct to calculate V(PG_ADJ,LOW)min that is Vout lowest threshold of PG turn low.

Best Regards.

  • 0
    TI__Genius 13245 points

    Hi Ushikubo-san,

    Q1: The default PG threshold (when PGADJ = GND) will be 89.6% (min), 94.6% (max) as a percent of VOUT.  So, for example, PG threshold for the 5.0 V device will be 5.0*0.896 = 4.48 V

    Q2: The correct tolerance is 2%

    Q3: Your equation #1 is correct for the falling threshold of PGADJ.  Hysteresis will cause PGADJ to trigger on the rising threshold approximately 2% HIGHER than the V(PGADJ_TH) specification (V(PGADJ_TH) = 1.067 (min), 1.163 (max)). 

    In other words, V(PGADJ_TH) describes the threshold voltage when PGADJ voltage is falling.  The threshold voltage is approximately 2% higher when PGADJ is rising.

    Regards,

    Mike

  • 0 in reply to Michael Hartshorne
    Mastermind 9620 points

    Hello Mike-san,

     

    Thank you very much for your quick response.

     

    I want to confirm my understanding and request of datasheet correction.

     

    Q1: V(PGADJ_TH)

    I asked about V(PGADJ_TH), but your answer is PG threshold (when PGADJ = GND) and I understand that I should use Vout=5V for the 5V device.

     

    Could you please answer original my question about V(PGADJ_TH)?

     

    Q2: V(PGADJ_TH) tolerance

    According to your answer that V(PGADJ_TH) tolerance is 2%.

    So could you please revise the datasheet as follows?


     

     

    Q3: V(PG_ADJ) rising and falling threshold calculation

    Q3-1:

    I may understand your advice.

    Could you please confirm if my understanding of how to calculate V(PG_ADJ) rising and falling threshold of attached file is correct?

     5023.TPS7B6850-Q1_V(PG_ADJ) rise and foll threshold.pptx

     

    Q3-2:

    Following explanation of datasheet contradicts with your answer.

    Could you advise if following modification is correct?

    Please revise datasheet if following is correct.

     

    Best Regards.

  • 0 in reply to Toshio Ushikubo
    Mastermind 9620 points

    Hello Mike-san,

     

    Please answer additional question.

     

    Q4: How to calculate V(PG_TH) threshold voltage

    You answered as following about V(PG_TH) threshold voltage.

     

    I want to reconfirm how to calculate V(PG_TH) min and max threshold of TPS7B6850-Q1.

    Please answer which calculation is correct, Case-1 or Case-2.

     

    Case-1

      V(PG_TH) min = 0.896 x 5V = 4.48V

      V(PG_TH) max = 0.936 x 5V = 4.68V

     

    Case-2

    According to the Vout tolerance +/-2%, Vout min = 4.9V and Vout max = 5.1V.

    Therefore

      V(PG_TH) min = 0.896 x 4.9V = 4.3904V

      V(PG_TH) max = 0.936 x 5.1V = 4.7736V

     

    Best Regards.

  • 0 in reply to Toshio Ushikubo
    Mastermind 9620 points
    Hello Mike-san,

    Please answer for my question Q1 to Q4.

    Best Regards.
  • 0 in reply to Toshio Ushikubo
    Mastermind 9620 points
    Hello Mike-san,

    I will have meeting with customer tomorrow, so I need as much as answer.
    Please answer for my question Q1, Q2, Q3 I posted on Jul 3 2017 and Q4 I posted on Jul 5 2017.

    Best Regards.
  • 0 in reply to Toshio Ushikubo
    TI__Genius 13245 points
    Hi Ushikubo-san,


    For Q1; V(PGADJ_TH) is specified separately from VOUT. It may correlate with VOUT, meaning that if VOUT is 1% low, V(PGADJ_TH) will also be low, but this should not be part of the calculation for the PG trip threshold.

    for Q2 and Q3: yes we can edit the data sheet to clarify. Your modifications are accurate according to the data I took on the bench.

    For Q4, the calculation from case 1 is correct.


    Please let me know what else is necessary to clarify.

    Regards,

    Mike
  • 0 in reply to Michael Hartshorne
    Mastermind 9620 points

    Hello Mike-san,

     

    Thank you for your answer.

    I will report your answer to customer today.

     

    Q3-1:

    Please answer if my calculation of following that I posted on Jul 3 2017 is correct or not.


     

     

    Q5: (additional question)

    For figure 22, V(PGADJ_TH) rising and falling threshold is as follows according your answer.

    How is V(PG_TH) rising and falling?

    Is following my understanding correct? If it is correct, could you modify the datasheet like following? I think it easy to understand the rising and falling threshold voltage of V(PG_TH) and V(PGADJ_TH)..


     

    Best Regards.

  • 0 in reply to Toshio Ushikubo
    Mastermind 9620 points
    Hello Mike-san,

    Please answer my question that I posted Q3-1 and Q5.

    Best Regards.
  • 0 in reply to Toshio Ushikubo
    TI__Genius 13245 points

    Hi Ushikubo-san,

    I'm very sorry, I checked further database parameters, and the information I gave previously in this post is not correct. The spec. VPG_ADJ is indeed 3%.  So, the data sheet values listed in the EC table is correct.

    The rising threshold is typically 26 mV higher than the falling threshold typical value (1.1 V).  So, rising threshold will be V(PGADJ_TH) + 26 mV.

    I'm sorry for the confusion.

    Regards,

    Mike

  • 0 in reply to Michael Hartshorne
    TI__Genius 13245 points
    Ushikubo-san,

    In addition to my post above and to answer Q3-1, the threshold value to use for the rising power good is not specified under min. and max conditions, because the hysteresis is not specified. However, the variation is small and the min. and max. can be very closely approximated as below.

    VPGADJ_TH RISING.
    1.067 + 26 mV (approximate min.)
    1.133 + 26 mV (approximate max.)

    The falling threshold values are as specified in the data sheet, so,

    VPGADJ_FALLING
    1.067 (min) and 1.133 (max).

    To answer Q5, VPG is specified at the RISING edge (as opposed to the FALLING edge, for VPGADJ_TH), then the hysteresis is 2% lower than the rising edge.

    So, VPG_TH RISING

    89.6% VOUT (min)
    93.6% VOUT (max)

    VPG_TH FALLING

    89.6% - 2% (approximate min.)
    93.6% - 2% (approximate max.)

    Your drawing is correct. I agree that the graph is not clear because the variable names to do not match the EC table variable names. We will submit these data sheet clarifications into the data sheet process flow.

    I hope this clarifies the questions.
    Regards,
    Mike
  • 0 in reply to Michael Hartshorne
    Mastermind 9620 points

    Hello Mike-san,

     

    Thank you for your answer.

     

    I clarified datasheet about V(PG_TH) and V(PG_ADJ) like attached.

    tps7b6850-q1_PG rising and falling threshold clarification.pdf

     

    1. Please check page 7, 13 and 14, and confirm if my understanding is correct.

    2. If you have finished the datasheet clarification, please give me pre-released datasheet to double check my understandings.

     

    I believe it’s important to submit correct information to customer to consider if TPS7B6850-Q1 satisfy requirement.

    So please cooperate.

     

    Best Regards.

  • 0 in reply to Toshio Ushikubo
    Mastermind 9620 points
    Hello Mike-san,

    Please answer my request.
    Customer needs correct understandings of threshold voltage to consider if they can use TPS7B6850-Q1 or not.

    Best Regards.
  • 0 in reply to Toshio Ushikubo
    TI__Genius 13245 points
    Ushikubo-san,

    Your summary is correct. Thank you for the accurate notes.

    Correcting the data sheet will take time, and we cannot post on E2E. I will make a friend request so we can move the data sheet off of E2E.

    Regards,
    Mike