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LMS8117A: LMS8117AMP-3.3/NOPB

Minseon Kim
Prodigy 10 points
Part Number: LMS8117A
Other Parts Discussed in Thread: TPS737, TLV759P

Tool/software:

Hi.

I'm going to use LMS8117A to make a system that regulates to 3.3V by receiving 3.6V. But The difference between the input and output voltages is not large, so it is difficult to be sure that they can be used.

Please check if it can be used for my design, and if it is difficult to use, please recommend LDO (small package, cheap price) that can output up to 1A.

  • 0
    TI__Expert 6640 points

    Hi Minseon,

    Thanks for reaching out. I assume 3.6V input is the steady-state Vin here -- What is the maximum input voltage rating the LDO is required to have?

    Also, to help address your question about dropout, can you share the ambient temperature range of your system? LDO dropout generally increases with increasing load and increasing temperature, so I'd like to account for this when looking for a device in our portfolio with <300mV dropout at 1A load.

    Regards,
    Kelsey

  • 0 in reply to Kelsey Farr
    Prodigy 10 points

    Hi. Thank you for your reply.

    The input 3.6V assumption is correct, and I will use it at 25 degrees room temperature. I think the tps737 series is suitable. However, I would like to use another device because it is expensive. Can you recommend it?

  • +1 in reply to Minseon Kim
    TI__Expert 6640 points

    Hi Minseon,

    Thanks for the details. I think TLV75901PDRVR is a good fit here.

    It is rated to 6.0V input, 1A output current, and can support 3.3V via ADJ output by setting FB resistors. The maximum dropout voltage for 1A load and Vout ≥2.5V is 270mV based on the Electrical Characteristics table, meaning that a differential of 300mV between LDO IN and OUT is sufficient for regulation.

    Nominal operating conditions of 3.6V Vin, 3.3V Vout, and 1A Iout, result in 0.3W of power dissipation across the LDO. Since TLV759P has a thermal resistance value of 80.3ºC/W (based on JEDEC standard PCB layout), this would result in an LDO junction temperature rise of +24ºC above ambient conditions. So, for the purposes of interpreting dropout performance graphs and other datasheet specs, TLV75901PDRVR would be ~50ºC in the application you describe.

    Regards,

    Kelsey