• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 62 subscribers
  • Views 292 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.

TPS543C20A: Required accuracy of resistance for selection pin

Taketo Sato
Genius 10365 points
Part Number: TPS543C20A


Hello team,

TPS543C20A requires E48 series resistors for some pin configuration. And 1% or better accuracy is recommended in datasheet.

When customer needs to use E12 series resistor they have to make the required resistance with combination of E12 resistors.

In this case, customer can make similar resistance value to E48 value though it will require multiple resistors with high accuracy, but not the same.

Does the part require pinpoint resistance such as E48 value with 1% error? or there maybe some more tolerance in actual?

Best regards,

  • 0
    TI__Expert 5310 points

    Hello,

    We do recommend E48 resistors with 1% or better tolerance for the pin strap configurations. The customer may use parallel combinations of E12 resistors to follow this recommendation. There is some tolerance with the pin configuration settings, but additional tolerance in the resistors may cause a slight variation in configurations regarding switching frequency and current limit in particular.

    Regards,

    Alec Biesterfeld

  • 0 in reply to Alec Biesterfeld
    TI__Genius 10365 points

    Hello Alec-san,

    Thank you for your comment.

    >additional tolerance in the resistors may cause a slight variation in configurations regarding switching frequency and current limit in particular.

    I understand additional tolerance in the resistor will create slight variation regarding switching frequency and current limit. How about RAMP(datasheet table3), VSEL(table2), SS(table1) and MODE(table5) pins configuration?
    What will happen if we fail to create E48 resistor value with 1% accuracy by combination of E12 resistors?

    If pinpoint resistance is really required, I think it may be strict requirement for some customers.

    Best regards,

  • 0 in reply to Taketo Sato
    TI__Expert 5310 points

    Taketo-san,

    If the resistors on RAMP, VSEL, SS, or MODE are too inaccurate, the device may select the wrong setting. For example, if the RAMP resistor is 187kohm with 20% tolerance and the resistance is 10-15% lower than the 187kohm value, then the device will likely select the 121kohm ramp capacitor. Those settings are discrete and each setting has a threshold near the specified resistance in the datasheet, so too high of a tolerance on the resistor may result in a different setting than expected. I think you should be ok with a E12, especially with a parallel combination.

    Regards,

    Alec Biesterfeld

  • 0 in reply to Alec Biesterfeld
    TI__Genius 10365 points

    Hello Alec-san,

    Thank you for your comment.

    Alec Biesterfeld said:
    Those settings are discrete and each setting has a threshold near the specified resistance in the datasheet,

    Is it possible for us to know the threshold just for information?

    or, is the threshold very close to 1% from the specified resistance?

    Best regards,

  • +1 in reply to Taketo Sato
    TI__Expert 5310 points

    Hi Taketo-san,

    I am not sure if they characterized the exact thresholds on this part. Usually they provide more than 1% margin from the thresholds, however the threshold may potentially lie 3-5% away from the specified value hence why we recommend 1% resistors. The best way to verify would be taking the part numbers with the tolerances that the customer intends to use and evaluating the performance on an EVM if they would like to sanity check their component selection. From TI's, point of view however, we feel strong recommending 1% resistors to ensure that the component value will not deviate above or below a pinstrap threshold.

    Regards,

    Alec Biesterfeld

  • 0 in reply to Alec Biesterfeld
    TI__Genius 10365 points

    Hello Alec-san,

    Alec Biesterfeld said:
    I am not sure if they characterized the exact thresholds on this part.

    Could you confirm with design team if the threshold is characterized or not, just in case?

    Best regards,

  • 0 in reply to Taketo Sato
    TI__Expert 5310 points

    Hi Taketo-san, 

    Design guarantees the specified pin strap thresholds in the datasheets and confirms the 1% tolerance across all units. There may be some unit-to-unit variation based on process, so it is possible that some units have slightly better/worse tolerance. If the parallel combination gets the customer to within 1% tolerance, that will suffice per design's recommendation.

    Regards,

    Alec Biesterfeld