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Questions of TPS65251(temperature characteristic,Load regulation,Line regulation)

Other Parts Discussed in Thread: TPS65251

I have questions about TPS65251.

Question 1.

Please tell me the output voltage temperature characteristic of the TPS65251.

      Example)    _% Vout/℃

Question 2.

In datasheet  P.6(Load regulation - DC  ΔVOUT/ΔIOUT),

Does it mean that  output  voltage shifts by 0.5% when output current is 3A?

Question 3.

In datasheet  P.6(Line regulation - DC  ΔVOUT/ΔVINB),

Does it mean that  0.5% of output voltage shifts when voltage changes from 4.5V to 18V?

  • Hi,

    1. Vout temperature characteristic is decided by Reference temperture Accuracy and FB divider resistor temperature Accuracy.

    TPS65251 can provide 1% Reference Accuracy under TJ = –40°C to 125°C & in alll corner condition. 

    For 2 & 3 question. the test condition as below:

    2. Load regulation:

    When load changes from 10%*Iout,max to 90%*Iout,max, Vout will change 0.5% in total.

    3. Line regulation:

    Under Iout=1A, when Vin change from 4.5 to 18V, Vout will change 0.5% in total.

    Besides, as for load regulation and line regulation, you can refer Figure9~14 in page 9.  

    zhao

  • Thank you for your answer.

    TPS65251 can provide 1% Reference Accuracy under TJ = –40°C to 125°C & in alll corner condition. 

    ⇒In datasheet p.6,accuracy of feedback voltage,

       Tj=25 : ±1%

       Vin=4.5 to 18V : ±2%

       Datasheet has written ±2%, Is the 1% reference accuracy  true when Tj is  –40°C to 125°C ?

    About Line regulation,

    Is "4.5V to 18V"  a change of DC?

    (changing from 4.5V to 18V or between 4.5V and 18V)

    and please tell me the relationship between "0.5% of line regulation" and "±2% of Vfb(4.5V to 18V).

    Besr regard

  • Hi, 

     1. Sorry, I forget to see the test conditon when VFB=+/-1%.

     According to datasheet, the TPS65251 can only provide 1% Reference Accuracy under Vin=12V, Tj=25deg, in all process corner condition.

    When Vin=4.5V to 18V, TJ = –40°C to 125°C, and in all process corner, VFB accuracy should be +/-2%.

    2. "4.5 to 18 V" means Vin changes between 4.5V and 18V, general speaking, during line regulation test, we sweep Vin from 4.5V to 18V, then record the MAX Vout variation.

    3.  "±2% of Vfb(4.5V to 18V)" means: during mass production, among lots of ICs, the MAX variation is +/-2% compare to typical value(0.8V).

    "0.5% of line regulation" means: When Vin sweep from 4.5V to 18V, in someone IC test, the MAX delta(Vout)/Vout is 0.5%.

    Take the figure9 for example, the average Vout=1.205V, the MAX delta Vout=0.005V, so line regulation=0.005/1.205=0.415%.

    BTW, the reason of Vout variation when do load regulation:

    When Vin sweeps from 4.5V to 18V, the DC gain of EA will change, and Error voltage between input of EA will also change accordingly, so it will result in Vout has variation.

    zhao  

  • Thank you for your answer.

    My customer wants to know worst accuracy(not typical) of output voltage when input voltage is 5~10.5V.

    Do you have the data about  worst accuracy  of output voltage?

    Best regards

  • Hi,

    I have checked, the line regulation parameter cannot be tested in ATE, it means we cannot measure the MAX value in mass production, so there is only typical value in EVM test.

    thanks.

    zhao

  • Thank you for your answer.

    Please tell me the output voltage variation (due to the influence of temperature and Vin) when we exclude variability (individual variability) among lots of IC.

    My customer wants to know the output voltage variation by change of temperature and input voltage after the IC enables.

    Best regards
  • Hi, TN

    I checked again, no found the test data.

    When temperature changes from -40C~125C, the variation mainly comes from reference variation, i have asked designer, the reference simulation variation is about 2~3mV, the bandgap voltage is ~1.2V, so the variation ratio is ~0.25%.

    So as for one IC, when Vin: 4.5~18V, Temp: -40C~125C, the output voltage total variation is about 0.5% + 0.25% =0.75%.  

    If considering the parasitic parameter on PCB, the total variation will be a little bigger. Just for you reference.

    My email: zhao-ma@ti.com

    We can dicuss by email if you have further question, then i can CC to more person.

    BR,

    zhao