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Differences between TPS74x01 LDOs

James Moser
Prodigy 30 points
Other Parts Discussed in Thread: TPS74801

I am trying to figure out which 1.5A regulator to use.  Specifically where x= 2, 3, 8.

I am looking for a ULDO linear regulator for 1.2Vin and 1.0Vout at about 1A.  The 1.0V rail is an analog rail to a 10Gbps device with IMPOSSIBLE to meet noise requirements (floor of 2.5nV/rtHz from 0 to 300MHz).  I want to get as low noise as possible.  The 1.2V is from a POL buck switching at 600kHz.

It looks to me that the 74301 has better PSRR but higher noise at 74801.  Not really sure how the 74201 fits in to the equation. 

Solution cost and size are relatively unimportant to me (I will be using lots of Cout).

Why do all 3 parts exist and why would I pick one over the other?

Fortunately, if I stick with the 5x5 QFN, they look to be pin compatible.

  • 0
    TI__Guru 50090 points

    HI James,

     

    The reason for the different parts is as follows:

     

    The TPS742xx and TPS743xx have a 1% tolerance on the regulated output voltage over line line and temperature. If you need a precise voltage rail, then these are the best choice. The difference between the TPS742xx and the TPS743xx is that the TPS742xx has soft start. This simply allows you to control the inrush onto your rail and given that you plan on using a lot of Cout, this might be a good idea. The TPS743xx has tracking which means the Vout can track or follow another voltage rail which can help with power rail sequencing.

    The TPS748xx is not as accurate at the output (2% vs 1%) and has a slightly higher Vdo at 1.5A.

    So if precision at Vout is not a concern, I would recommend going with the TPS74801.

    And yes, if you want to choose the 5x5 package, then they are pin compatible.

    I hope this helps.

     

    Regards,

     

    John