• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 21 subscribers
  • Views 348 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TXS02612: Can VCCA and VCCB0,B1 be power up at the same time?

Hiroaki Yuyama TED
Expert 1740 points
Part Number: TXS02612


Tool/software:

Dear, Logic Support members.

I am an FAE at a Japanese distributor.
One of our customers has asked me about power sequencing.

It says, "Apply VCCB0 and VCCB1 only after the VCCA power supply is applied."
Is it okay to supply VCCA and VCCB simultaneously from Simplified Architecture?
Best Regards,
Hiroaki Yuyama
  • 0
    TI__Mastermind 43061 points

    Hi Yuyama-san,

    No concerns if VCCA/ VCCB ramp up at the same time. The only concern is in the event that VCCB is ramped up first, which may potentially result in glitches at the outputs due to the internal control circuitry referenced to VCCA. 

    Regards,

    Jack 

  • +1 in reply to Jack Guan
    Expert 1740 points

    Hi Jack-san,

    Thank you for your reply.

    I followed your advice and provided feedback to the customer.

    I told them that there is no problem with simultaneous power-up sequence,
    but that they should be careful because problems can occur if the VCCB port is supplied first.

    Best Regards,
    Hiroaki Yuyama

  • 0 in reply to Hiroaki Yuyama TED
    Expert 1740 points

    Hi Jack-san,

    Thank you for your support.

    We have received additional questions from the same customer.

    1. For this customer, VCCA (1.8V) and VCCB (3.3V) are enabled at the same time.
    The VCCA and VCCB DCDC converters also take 2.7ms to start up due to the Soft start function.
    As a result, VCCB reaches 1.1V about 0.8ms earlier than VCCA.
    "VCCB" starts up faster, but is there any problem with using it?

    I have attached a graph of the power-up sequence.

    2. If the power-up sequence in 1 is NG, is it correct to understand that an operation error will occur but not a malfunction?

    The e2e forum stated that glitches will occur.
    If VCCA starts up earlier, are there any problems with operation after starting at the minimum operating voltage of 1.1V?

    Best Regards,
    Hiroaki Yuyama

     

  • 0 in reply to Hiroaki Yuyama TED
    TI__Mastermind 43061 points

    Hi Yuyama-san,

    Hiroaki Yuyama TED said:
    If the power-up sequence in 1 is NG, is it correct to understand that an operation error will occur but not a malfunction?

    Yes there is a possibility that a glitch can occur- note that it is only in the time window when VCCB is ramping up before VCCA, and normal operation can be expected once both power supplies are fully ramped up. 

    Hiroaki Yuyama TED said:
    If VCCA starts up earlier, are there any problems with operation after starting at the minimum operating voltage of 1.1V?

    Validation of this part did not cover this corner during test across PVT- however, it is best practice to only start operation once VCCA/ VCCBx is fully ramped up. 

    Regards,

    Jack 

  • 0 in reply to Jack Guan
    Expert 1740 points

    Hi Jack-san,

    Thank you for your support.

    Validation of this part did not cover this corner during test across PVT,
    so we do not know what will happen in mass production with a power supply sequence where VCCB is turned on first,
    so we ask the customer to comply with the "POWER-UP CONSIDERATIONS" in the data sheet.
    We advised the power supply FAE to delay the soft start so that VCCA can be turned on first.

    Best Regards,
    Hiroaki Yuyama

  • 0 in reply to Hiroaki Yuyama TED
    TI__Mastermind 43061 points

    Hi Yuyama-san,

    My comment earlier for the Test not covered was regarding the condition where translation operation is attempted as soon as VCCA crosses 1.1V before finally becoming stable at 1.8V. 

    For this condition however:

    Hiroaki Yuyama TED said:
    so we do not know what will happen in mass production with a power supply sequence where VCCB is turned on first,

    Glitches are expected if VCCB is ramped up before VCCA, due to internal control circuitry being referenced to VCCA (note that these glitches are only prevalent during this ramp up period. Once both power supplies are ramped up, the glitches mitigate. If glitches are not a concern to customer during ramp up, then the device is OK to use in this state). 

    Please let me know if I am understanding your concerns differently. 

    Regards,

    Jack