• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 741 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.

TPS7A4700 and TPS7A3301 equivalent package?

min zhou
Prodigy 105 points

Hi,
I have difficulties in soldering these two QFN devices. The footprint I designed is easy to cause short.
Since I have failed many times, I want to ask if there are any other equivalent packages of the chips? There is a KC package for the TPS7A3301 while I do not find any other package for TPS7A4700. Do you have any more information?

Another question if I have designed the output of the regulators to be +/- 15V, I am wondering the max input voltage we can apply. And also the optimal input voltage range for this? I have tested 21 or 22 V is fine. But will it degrade the functionality if the input and output voltage difference is that large for a long time? What if the input voltage is 25V above? will it damage the device?

Thanks very much!


Best,

Min

  • 0
    TI__Guru 55940 points
    Hi Min,

    TPS7A4700 is only available in the QFN package at this time.

    You need to look at how much power will be dissipated in order to know what your maximum Vin can be. You will need to limit the voltage drop across the LDO so that the power dissipated will not cause the junction temperature to exceed 125C. I can help you with this calculation, but first I need to know more about your load current. What is your maximum load current going to be?

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 105 points

    Hi Ryan,

    Thanks very much! I have designed TPS7A4700 output is 15.9V, And TPS7A3301 to be -15.4V. The output current can be varied. While my input voltage can be up to 21 V, could you please calculate for me the maximum output current if the input voltage is 19, 21 and 22 V respectively? Thank you!


    Best,

    Min

  • 0 in reply to Ryan Eslinger
    Prodigy 105 points
    Hi Ryan, your comment on that "the junction temperature should not exceed 125C." remind me a concern that when I soldered the chip with lead free solder where the temperature was 750F. Will the soldering process damage the chips? Could this be one of the reasons I failed many time by soldering myself? Thanks!
  • 0 in reply to min zhou
    TI__Guru 55940 points

    Hi Min,

    The MSL, Peak Temp column in the Packaging Table of the Package Option Addendum (the first addendum after page 23 of the datasheet), shows a peak solder temperature of 260C.  This is true for both devices.  Alternatively you can find this on the Quality & packaging tab of the product page: 

    The process to determine the max load current you can use is described in Section 9.1 of the TPS7A4700 datasheet.  As you are trying to solve for current, you will need to start with Equation 8 of that datasheet (Tj = Ta + (thetaja * Pd)).  Thetaja is given in the datasheet's thermal information table (32.5C/W).  Tj should be the maximum operating junction temperature (125C).  Ta is the ambient temperature that your application will be subjected to.  In this example, I will assume 25C.  Solve this equation for Pd (the power dissipated). Pd = (125C - 25C) / 32.5C/W = 3.08W.  This is the maximum power that you can dissipate in the LDO and remain within the operating temperature range.

    Next use Equation 7 (Pd = (Vin - Vout) * Iout).  You gave Vout as 15.9V and Vin as 19V.  We just solved for Pd above as 3.08W.  Iout = 3.08W / (19V - 15.9V) = 993mA.

    You can repeat this process for all of the conditions you are interested in for any LDO.

    Very Respectfully,

    Ryan