Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 65 subscribers
  • Views 227 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.

Original question:

TPS561201: Same Schematic with 3A ver.

TPS561201: TPS561201: Same Schematic with 3A ver. (Move to Internal)

Hideki Hayashi1
Expert 7420 points
Part Number: TPS561201
Other Parts Discussed in Thread: TPS563201,

Hi team,

Can you please take a look into the attached schematic with TPS563201 to comment if they can reuse passive components with TPS561201?

Best regards,

Hayashi

  • 0
    TI__Genius 13451 points

    Hi Hayashi!

    Just based on above information, it can reuse.

    Shuai

  • 0 in reply to Shuai Fan
    TI__Expert 7420 points

    Hi Shuai,

    Customer's in/out is 14.5Vin_max, 5Vout, 600mA max. When I substitute these value into equation (4) to calculate Iripple

    Iripple = 5/14.5 * (14.5-5) / (3.3u * 580k) = 47.5/14.5 * 1/(3.3*0.58) = 1.71A

    So Iripple/2 = 0.86A. Because minimum current limit is 1.2A, customer should change the inductor to higher value, correct?

    When change to 4.7uH, Iripple/2 = 0.60A. It is few margin.

    When change to 6.8uH, Iripple/2 = 0.41A. It is guessed as OK. But is there any concern?

    Overall, is there any mistakes on what I calc?

    Regards,

    Hayashi

  • 0 in reply to Hideki Hayashi1
    TI__Expert 8100 points

    Hi Hideki,

    My colleague will give you reply by tomorrow!

    BRs

    Zixu

  • 0 in reply to Zixu Wang
    TI__Genius 13451 points

    Hi Hayashi!

    This device is valley inductor current protection. As long as your average current doesn't exceed 1.2A, 3.3uH can work.

    It suggests to add c108 with 10-30pF for stability.

    Shuai

  • 0 in reply to Shuai Fan
    TI__Expert 7420 points

    Hi Shuai,

    I read the datasheet and found below, which seems confliction with your comment

    If the monitored current is above the OCL level, the converter maintains low-side FET on and delays the creation of a new set pulse, even the voltage feedback loop requires one

    I understands as below

    After HSFET On-time, LSFET will on and detect overcurrent immediately because the switch current (Iload + Iripple) exceeds OCL threshold (1.2A min). Then LSFET on-time is longer than Duty_off / fsw since LSFET keeps on until the overcurrent condition is removed. When the device repeats it in every switching period, the output voltage will be lower due to longer off-time.

    Is my understanding correct?

    Regards,

    Hayashi

  • 0 in reply to Hideki Hayashi1
    TI__Genius 13451 points

    Hi

    Your average current is just 0.6A. When inductor current from 1.7A to 1.2A, OCL protection will  be triggered, LSFET will have the highest priority to turn on. 

    One current be lower than 1.2A, protection logic will be canceled. The turn on/off behavior of LSFET will determined by normal logic. It will not affect the duty cycle.

    Assume it doesn't exist OCL protection, the behavior is the same.

    If customer still have concern, it is better to use 6.8uH. It is ok at my side.

    Shuai