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TPS543B20: VSEL AND RILIM Resistors Need

vikas gupta1
Intellectual 525 points
Part Number: TPS543B20

Hi,

I am designing 1.05V output with 10A current using TPS543B20. Please help me with the below points:

1. I understand from datasheet VILIM= RILIM*IILIM, Please help me to choose the RILIM resistor value, not getting any references in datasheet. What VILIM value we can take to calculate?

2. On page8 of datasheet, i see table to select VSEL resistor value, can you please help me for 1.05V we choose 121Kohm. Do we need feedback resistors to configure the output voltage or the IC can take VSEL voltage in output?

3. Please help me with the Soft Start requirment, is it dependent on Target IC or we can configure locally in TPS543B20, which way it helps better.

Thanks

Vikas G.

  • 0
    TI__Guru**** 191445 points

    Vikas,

    The RILIM selection is detailed in section 8.4.13.1 in the datasheet.  It is low side valley current limit, so the dc output current limit is valley current limit set point plus one half of the peak to peak inductor current.

    For the 1.05 V case, you do not need external feedback resistors.  You can connect the load directly to RSP and RSN.

    You will configure the soft-start locally at the TPS543B20 SS pin strap selection pin.  There are 10 options available.  You may pick any one you want.  Just make sure it is not so fast that current limit occurs during the slow start time.  Please remember that a constant current is required to linearly ramp up the output voltage:

    I = Cout * Vout / tSS

    Plus what ever curent is drawn by your load during start up.

  • 0 in reply to JohnTucker
    Intellectual 525 points

    Hi ,

    Please help me one critical requirement we have, In order to achieve 0.5% accuracy of DC output, what considerations we need to take care any specific need or recommendations for TPS543B20. We have Vin= 12V and Vout=1.05V.

    Thanks

    Vikas G.

  • 0 in reply to vikas gupta1
    TI__Guru**** 191445 points

    Vikas,

    121k is the correct pin strap resistor for 1.05 V output.  The initial tolerance for TPS543B20 is +/- 0.5 %, so you will need to minimize any external losses.  You will need to be very careful with your layout.  Look at the layout guidelines in the data sheet and the layout of the EVM in the users guide:

    www.ti.com/.../sluubo0.pdf

  • 0 in reply to JohnTucker
    Intellectual 525 points

    Hi,

    Just like to add up SoftStart time for the part TPS543B20 is any way dependent on to achieve accuracy of 0.5%,any recommendation to select the soft start resistor for the same.

    Thanks

    VIkas G.

  • 0 in reply to vikas gupta1
    TI__Guru**** 191445 points

    Vikas,

    Table 1 in the data sheet lists the allowable soft start times and the required resistor value for each option.  SS time does not affect the output voltage accuracy once the SS time is completed.