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LP38692-ADJ: Schematics Review

Desireddy Teja Reddy
Intellectual 490 points
Part Number: LP38692-ADJ

Hi Team,

We are using the LP38692SD-ADJ/NOPB LDO part in our schematics. This part we are using in couple of instances. I had attached the schematic Images below, Kindly review the schematics and share your valuable feedback with us.

Thanks and Regards

- Teja

  • 0
    TI__Expert 4450 points

    Hello Teja,

    A few comments for both schematics. There is a Feed-forward capacitor, which improves transient, noise, and PSRR performance, but is not required for regulator stability. Please refer to this app note for detailed description of Cff tradeoffs: https://www.ti.com/lit/pdf/SBVA042. And, what current is being driven in each circuit? The reason I am asking is to be able to calculate power dissipation in order to determine the maximum allowable ambient temperature for the device. Lastly, for the schematic of Vout = 5V, make sure voltage on enable is above 3V.

    A general comment LP38692-ADJ is an old device, I would recommend switching to a newer device like TLV759P or TLV767 if higher Vin needed.

    Best,

    Eunize Tobias

  • 0 in reply to Eunize Tobias
    Intellectual 490 points

    Hi Eunize Tobias,

    Thanks for your valuable Feedback. As per your instructions we had removed the feed forward capacitor. For the schematic Vout is 5V the enable voltage is 3.3 which is above 3Volts. The current Driven for Vout = 3.3V circuit is 0.00004 A   and for the circuit Vout = 5V is of 0.03 A.

    Please refer the attached image below for the Updated schematics.

    Thanks and Regards

    - Teja

  • +1 in reply to Desireddy Teja Reddy
    TI__Expert 4450 points

    Hello Teja,

    Just to clarify I didn't recommend removing feed-forward capacitor. I just mentioned it wasn't required for the device stability and that there are some cons and pros of using it. Based on that it depends on the application and user decision if want to keep it on design or remove it. 

    Thank you for clarifying the current load for the devices. Schematics look good taking into consideration the thermal resistance (Roja) is in accordance with EIA/JEDEC JESD51-7 standards. Meaning I calculated the power dissipation with Roja = 50.6°C/W recorded on datasheet which includes 4 thermal vias under the exposed thermal pad. You can refer to section 8.2.2.5 Power Dissipation of datasheet for more detailed information. 

    Best,

    Eunize Tobias