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TPS7A89: Junction temp rise

Saadya M.
Prodigy 40 points
Part Number: TPS7A89

Tool/software:

I want to use the TPS7A89 such that Vin = 5.6V and Vout=5V, for each of its two outputs (on at the same time).

I want to keep the junction temp of the whole part below 100C.  when I calculate the Trise, should I use the total current (sum of the current from each of its outputs) or should I be doing that calculation with only the max current from each LDO output?

So, for example, if Rja = 33 dec/W, and I am supplying 1A from each output of this part, is the Trise = (0.6) X (1A) x 33 = 19.8 deg C ?

  • 0
    TI__Guru 50025 points

    Hi Saadya,

    The total junction temperature rise is the sum of both channel, i.e. Trise = 0.6V * 2A * 33C/W = 39.6C. Note that you can also improve on the RθJA using good layout practice, but conversely, you can also reduce the RθJA with poor layout. Here's an app note with an empirical look at the impact of board layout:

    An empirical analysis of the impact of board layout on LDO thermal performance: https://www.ti.com/lit/an/slvae85/slvae85.pdf

    What is your application max ambient temperature? 

    Regards,

    Nick