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LM317: Recommended part#

Jun Ishida
Expert 5640 points
Part Number: LM317
Other Parts Discussed in Thread: TLV767, TPS562201

Hi team,

The customer would like to use a linear regulator with adjustable output for 12Vin -> 5Vout/1A and 12Vin -> 7Vout/1A, respectively. The current solution is NJM2387ADL3. Could you provide the recommended part# of a linear regulator to meet above conditions?

Regards,

Jun

  • 0
    TI__Intellectual 1200 points

    Jun,

    The recently released TLV767 device should fit the application needs listed above, however we may need further information about the application to ensure it is a good fit.

    Can you provide additional details about the application needs here? Is the 1 A of current continuous or is this only needed for short periods of time?

  • 0 in reply to Blake Soileau
    TI__Expert 5640 points

    Hi Blake-san,

    I think TLV767 may have thermal issue when used for 5V or 7V dropout, but how do you think? 7Vout is for optical and 5Vout for analog and internal circuit.

    Regards,

    Jun

  • 0 in reply to Jun Ishida
    TI__Guru 55940 points
    Hi Jun-san,

    You are correct that due to the high headroom (Vin - Vout) of your application, we do need to consider the thermal implications. This is true for any linear regulator. Application conditions such as headroom (Vin - Vout), output current profile, layout, proximity to other heat sources, and ambient temperature will play a role in the thermal performance of the application. To the question posed by , are you requiring a continuous current of 1 A or is this your peak current? While it is important to select a linear regulator that is rated for the peak current, it is important to know the nominal output current as well when estimating the thermal implications.

    Keep in mind that the primary heatsink for TLV767, like most linear regulators, is the PCB board itself. As such, maximizing the GND copper local to the TLV767 will allow you to achieve the best thermal performance.

    It is also possible to improve the thermal performance of your application by creating a mid-rail between 12 V and 7 V. This will reduce the power dissipation in the linear regulator. You can do this using a switching dcdc for the best efficiency or by using two linear regulators in series for higher system PSRR. In both cases you will have less power dissipated in each regulator.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Expert 5640 points
    Hi Ryan-san,

    Thank you for your advice. Yes, we already proposed TPS562201 for the socket but they need to consider of the linear regulator solution as well. Could you provide the recommended part# for both 1A continuous current case and 1A peak current case, respectively?

    Regards,
    Jun
  • 0 in reply to Jun Ishida
    TI__Guru 55940 points
    Hi Jun-san,

    A continuous 1 A current with your application headroom (Vin - Vout) will be too much power dissipation for a linear regulator without a lot of external heatsinking.

    We would not recommend a regulator for the full headroom with a continuous 1 A load. If your customer will use TPS562201 to reduce the input voltage local to the regulator, then TLV767 will be a good option for this socket.

    If it is only 1 A peak current, TLV767 may still be a good solution depending on the load profile. We would still recommend lowering the input voltage local to the linear regulator in order to reduce the power dissipation within the regulator.

    Very Respectfully,
    Ryan