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TPS7A85A: Connection at adjustable output mode

Roy Hsu
Intellectual 2880 points
Part Number: TPS7A85A

Hi Team,

My customer use TPS7A85A as adjustable mode, but their connection have some problem, could you help me check if below  connection is workable?

Output setting as 1.8V, and feedback connect a 9.68k ohm, using internal 12.1k ohm + 9.68k ohm as resistor divider as below. (Please ignore input 1.4V and output 0.9V, suppose input is 2.5V and output is 1.8V). all ANY OUT voltage setting pins are floating (unused).

Best Regards,

Roy

  • 0
    TI__Mastermind 34055 points

    Hi Roy,

    In general we do not recommend using one of the internal ANYOUT resistors along with an external resistor.  See this note below the block diagram:

    We recommend using 2 internal ANYOUT resistors or 2 external feedback resistors to set Vout.

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    TI__Intellectual 2880 points

    Hi Stephen,

    Do you have the tolerance about the 12.1k ohm inside TPS7A85A? I think it have tolerance then customer can determine if they still use it or not.

    Because my customer’s connection as above picture shows, I think if use external resistor divider at least it should cut the top or bottom layer from SNS to Vout, and if the net is not top or bottom layer they can not use external resistor divider, so please let me know the tolerance about the 12.1k ohm inside it.

    If you have any other suggestion please also let me know, for use any output mode because those any output pin are floating so can not use.

    Thanks.

    Best Regards,

    Roy

  • 0 in reply to Roy Hsu
    TI__Mastermind 34055 points

    Hi Roy,

    Unfortunately I don't have the tolerance, I suspect it's larger than what we are used to with discrete resistors.  The tolerance is not as important as the laser trimming between the different ANYOUT resistors.  They may have wide tolerance by themselves, but the laser trimming enables very accurate Vout which is what customers usually want to see.

    If you cannot create 1.9V using the ANYOUT then I would recommend using discrete resistors to set the setpoint.

    Thanks,

    Stephen