• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 206 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

UCC256402: wake up time UCC256402

Ola Baath
Prodigy 40 points
Part Number: UCC256402

Hi,

The wake up time for the UCC256402, how long is this normally and does the timer only start once the voltage on the BLK pin being above the threshold?

Right now I measure a wakeup time of about ~3 ms.

Kind regards,

  • 0
    TI__Mastermind 26225 points

    Hi Ola,

    When voltage is applied to the HV pin, it will immediately begin to charge up VCC. The LLC will not start switching however until the BLK pin exceeds 3V.

    For the LLC to begin soft start, two criteria needs to be satisfied:

    1. VCC has successfully charged up to 26V and the VCC voltage has not yet fallen to the VCCRestartJfet threshold (9.65V typical)

    2. BLK exceeds the BLKStart threshold of 3V.

    If VCC falls below the VCCRestartJfet threshold, then the controller will charge up VCC back to 26V before it moves to the soft start phase. The soft start time only begins when both conditions are satisfied. I couldn't see your attached images but the 3ms number is typical for the soft start time (not including the time needed to charge up VCC to 26V or the time for BLK to exceed 3V). Normally the soft start time itself is in the range of few ms to ~10 or 20ms or so but this is dependent on how the LL/SS parameters are selected. 

    Best Regards,

    Ben Lough

  • 0 in reply to Benjamin Lough
    Prodigy 40 points

    Hi Ben,

    I tried to attach two images but something apparently went wrong. I didn't mean the soft start timing. I meant the wake-up time, this can be seen depicted in figure 49 in the datasheet.

    Kind regards,

    Ola

  • 0 in reply to Ola Baath
    TI__Mastermind 26225 points

    Hi Ola,

    Thanks for the clarification. The wakeup time would be dominated by the programming time of the BW option. This time is 2ms typical. This time would begin once BLK is >3V and VCC has already been charged up to 26V and is still greater than the VCCRestartJfet threshold.

    Best Regards,

    Ben Lough