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TPS6281320Q

user6090272
Prodigy 90 points
Hi Expert.
Two patterns of the circuit using TPS6281320QWRWYRQ1 were designed.
Could you confirm that there are no problems with inductor constant and output capacitor constant?
Please refer to the "No 10" sheet.
Best Regards,
W.Makimoto
TPS6281320QWRWYRQ1 門連票_NO10表シート.xlsx
  • 0
    TI__Genius 17301 points

    Hi,

    Capacitors look ok but the inductor value is too high than the datasheet recommendation. Please follow the table 6 in the datasheet for inductor selection.

    Best regards,

    Tanvee

  • 0 in reply to Tanvee
    Prodigy 90 points
    Hi Expert.
    Is the pattern 2 too large for the inductor constant?
    Is the pattern 1 OK? "
    "About the inductor constant
    Follow Table 6 in the data sheet. , But
    Please tell L value how much L value should actually be.
    The conditions are as follows.
    1 Vout = 1.21 to 1.13 V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 3079mA / TYP: 1500mA
    Fs = 2.025 to 2.475 MHz [with SSC]
    2 Vout = 1.44 to 1.56 V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 866mA / TYP: 343.9mA
    Fs = 2.025 to 2.475 MHz [with SSC]
    Previously, when asked about the inductor constant method, it was calculated by “ΔIL (max) <= 0.2 IOUT (max)”, and Pattern 1 was answered with 0.56 uH.
    Pattern 2 selected 2.2uH according to the condition, but it is too large, so please tell L value how much L value should actually be.
    Follow Table 6 in the data sheet. It can not be judged by the answer with
    Could you show me the actual numbers? "
    Best regards,
    W.Makimoto
  • 0 in reply to Tanvee
    Prodigy 90 points
    Hi Tanvee.
    Is the pattern 2 too large for the inductor constant?
    Is the pattern 1 OK? "
    "About the inductor constant
    Follow Table 6 in the data sheet. , But
    Please tell L value how much L value should actually be.
    The conditions are as follows.
    1 Vout = 1.21 to 1.13 V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 3079mA / TYP: 1500mA
    Fs = 2.025 to 2.475 MHz [with SSC]
    2 Vout = 1.44 to 1.56 V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 866mA / TYP: 343.9mA
    Fs = 2.025 to 2.475 MHz [with SSC]
    Previously, when asked about the inductor constant method, it was calculated by “ΔIL (max) <= 0.2 IOUT (max)”, and Pattern 1 was answered with 0.56 uH.
    Pattern 2 selected 2.2uH according to the condition, but it is too large, so please tell L value how much L value should actually be.
    Follow Table 6 in the data sheet. It can not be judged by the answer with
    Could you show me the actual numbers? "
    Best regards,
    W.Makimoto
  • 0 in reply to user6090272
    TI__Genius 17301 points

    Hi Makimoto,

    The inductor value should not be higher than the max value suggested in datasheet table7.3. According to me, a 600nH inductor is good enough and if you are concerned about the output ripple, it can be reduced using the output cap. If you would like to check different conditions I would recommend to use webench model which can help you to select the parameters for your design.

    Best regards,

    Tanvee

  • 0 in reply to Tanvee
    Prodigy 90 points

    Hi Tanvee

    "Thank you for your reply.
    "This is enough with a 600 nH inductor."
    Is this the result of calculation under the following conditions?

    ·conditions
    Vout = 1.44 to 1.56V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 866mA / TYP: 343.9mA
    Fs = 2.025 to 2.475 MHz [with SSC]
  • 0 in reply to user6090272
    TI__Genius 17301 points

    Hi,

    I would suggest following the section 10.1.3 in datasheet about the inductor selection. Normally the 0.47uH inductor is typically suggested for design but inductor value is selected according to the inductor current ripple. So, if you required low current ripple, I would suggest using higher inductor value but it should be in the range of datasheet specification. So, inductor value is flexible within range given in table7.3 in the datasheet but it depends on your application.

    Best regards,

    Tanvee

  • 0 in reply to Tanvee
    Prodigy 90 points

    Hi,

    "I have been asking you the same question many times,
    The answer can not be found in the data sheet section 10.1.3.
    I am not sure if you look at section 10.1.3 of the data sheet, so I am asking you questions.

    Question
    What should the inductor value be in the following conditions?
    Could you tell me the inductor value?

    ·conditions
    Vout = 1.44 to 1.56V
    Vin = 3.8 to 4.2 V
    Iout = MAX: 866mA / TYP: 343.9mA
    Fs = 2.025 to 2.475 MHz [with SSC]


    If you ask me a question before, I would like to answer “ΔIL (max) <= 0.2 IOUT (max)”,
    As a result of having calculated it, it became 2.2uH,
    The following answer was received: "Please do not make it larger than the maximum value shown in Table 7.3 of the data sheet."
    After all, how can you calculate the inductor value under the above conditions? "
    Best regards,
    Makimoto
  • 0 in reply to user6090272
    TI__Genius 17301 points

    Hi Makimoto,

    First, the equation provided in the datasheet is for inductor ripple and the max inductor current calculation not for inductor value calculation. The ripple value change for each case and application. Your condition  ΔIL (max) <= 0.2 IOUT (max) will not satisfy for all cases. For the second case, the ripple value will be higher and this is the main reason I was asking about inductor ripple requirement in your application. You can choose any inductor between 0.33uH to 0.9uH but the inductor ripple will change. I would suggest you can use 600nH but than  ΔIL (max) <= 0.8 IOUT (max).

    I am closing this thread and I would like to have a further discussion through email. 

    Best regards,

    Tanvee