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TPS2492: Power Limit

LIN
Intellectual 410 points
Part Number: TPS2492
Other Parts Discussed in Thread: TPS24751

TPS2492 measures external FET VDS by VOUT-VSENSE, and voltage across RSENSE by VSENSE-VCC.

Without knowledge of RSENSE, how does TPS2492 determines the power dissipation on the external FET in order to impose power limit?

Thanks.

 

  • 0
    TI__Guru** 105361 points
    Hi Aibing,

    I will get back to you shortly on this.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    TI__Guru** 105361 points
    Hi Aibing,

    Can you share your target design specifications.

    The functional block diagram and the final calculation expressions are kept simple in the datasheet for ease.
    Good to see your interest on the control loop details. I suggest to look at Figure 34 in TPS24751 datasheet, this device also uses same control method. As you see in the Figure 34, the sense voltage gets applied across the RSET and scales down the load current, this current is forced through Rimon and is used for control. So, actual values are not important for the loop control. The ratio of Rimon/Rset is important.

    For TPS2492 device, both Rimon & Rset are internal and fixed. Let me know if you have any followup questions.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Intellectual 410 points

    Hi Rakesh,

    Thanks.

    Also I have a look at the formula for power limit again, VPROG = PLIM / (10 x ILIM),

    RSENSE appears in both PLIM and ILIM calculations, and is eliminated in the formula above.