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LP38503-ADJ: The maximum output current rate of this LDO regulator is not supported in the webench design.

Furkan Uysal
Prodigy 10 points
Part Number: LP38503-ADJ

Hi, 

I want to use LP38503ATJ-ADJ/NOPB to get 3.3V output voltage at 3A from 5V input voltage. The values specified in the datasheet of the IC are as follows:

  •  Input Voltage: 2.7 V to 5.5 V
  • Adjustable Output Voltage: 0.6 V to 5 V
  • Ensured Output Current of 3A

However, the output voltage of 3.3V at 3A cannot be designed in Webench Power Designer. What is the reason for this? It can create a circuit that can provide a maximum output current of 1.5A at 3.3V. So I can't use this IC for 3.3V output voltage at 3A? There seems to be a conflict between the datasheet and webench? I would be grateful if you answer my question. Waiting for your suggestions.

  • 0
    TI__Guru 50025 points

    Hi Furkan,

    Webench has built into it the thermal characteristics of the parts. The limitation you are seeing is due to the high power dissipation that comes with dropping the voltage from 5V to 3.3V while driving 3A. The power dissipated in the LDO in this application would be (5V - 3.3V) * 3A = 5.1W, and with the better thermal performance of the NDQ package (33.3C/W), this would correspond to a 170C junction temperature rise. You will need to select a part that has better thermal performance for this application.

    Regards,

    Nick