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TPS7A3301EVM-061: Power dissipation problem

Nandkishore Parmar
Prodigy 10 points

Part Number: TPS7A3301EVM-061

I designed a 4 channel +/-3.3vdc power supply board using tps7a3301 and tps7a8300. Each channel has 750mA loads. There are 4 tps7a3301 ic for each channel and 2 tps7a8300 ic sharing between 2 channels. The board has 4 layers , in which there is one ground plane.

Input supply is +/-5v , I checked ripples and noise is ok in individual channels, but when I connect the loads in all 4 channels , the board is getting too much hot, my concern is how to get overcome this problem. The ground plane is inner layer. Please help me.

  • 0
    TI__Expert 4350 points
    Hi Nandkishore,

    Each channel will dissipate 2.55 W:
    Pdiss = (Vin - Vout) * Iout = (5 V - 3.3 V) * 0.75 A = 1.275 W (positive rail)
    Pdiss = |(-5 V - -3.3 V)| * Iout = 1.275 W (negative rail)
    4 channels will dissipate 10.2 W. This is a lot of power for a single board.

    There are some options to either reduce the power dissipation or conduct it out of the board:
    - Reduce the input voltage from +/- 5 V to a lower voltage to reduce the power dissipated in all of LDOs. If you change the input voltage to +/- 4 V, then the total board dissipation is 4.2 W. This is a 59% reduction in dissipated power.
    - Conduct the heat out of the board using heat sinks, fans, etc. You will have to modify the board layout and have exposed copper on the top and bottom surface with thermal interface material to conduct heat to a heat sink. Fans to blow air through the heat sink will help, too.
    - Consider using the TO-220 version of TPS7A33 with heat sink connected to the tab of the LDO.
  • 0 in reply to Eric.Preiss
    TI__Expert 4350 points
    Hi Nandkishore,

    I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.