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TPS546D24A: TPS546D24AEVM-TI Fusion Current waveform

Gajendiran A
Prodigy 225 points
Part Number: TPS546D24A

Hi 

I have connected the external load with TPS546D24AEVM (single phase) and monitored the current consumptions on the TI fusion tool with different loads (1A,2A,3A,4A,5A, and 6A). The current showing on the tool is not a match with the load. 

TI EVM -0.9V (Vout )
External Load (A) TI-Fusion waveform (A)
0 -1.16
1 -0.16
2 0.81
3 1.81
4 2.81
5 3.81
6 4.81
TI EVM -0.8V (Vout )
External Load (A) TI-Fusion waveform (A)
0 -1.18
1 -0.16
2 0.78
3 1.77
4 2.77
5 3.77
6 4.77
TI EVM -0.5V (Vout )
External Load (A) TI-Fusion waveform (A)
0 -1.44
1 -0.44
2 0.53
3 1.52
4 2.52
5 3.53
6 4.53
  • 0
    TI__Guru 54580 points

     

    Since there is no single phase TPS546D24AEVM, I will presume that you mean that you have converted the TPS546D24AEVM from a 2-phase into single phase operation using the instructions provided in it's users guide.

    However, I do not see a question in your post, and the reported currents are with the expected tolerances of the TPS546D24A's -20A to +63A current monitoring circuitry.

    If you wish to compensate for the residual offset of the current sense, you can program IOUT_CAL_OFF to +1.2A and store that offset setting to NVM.

  • 0 in reply to Peter James Miller
    Prodigy 225 points

    Peter,

    Yeah.I have converted EVM to a single-phase operation.

    The question is why the fusion design tool is not showing the correct current. Anyway, you answered that we could set the offset current... and another question is why the different outputs (0.8V,0.9V,0.5V) has different offset current with 0.8V is 1.18A,0.9V is 1.16A and 0.5V is 1.4A?

  • 0 in reply to Gajendiran A
    TI__Guru 54580 points

     

    Gajendiran A said:
    The question is why the fusion design tool is not showing the correct current.

    FUSION is reporting the value of READ_IOUT provided by the TPS546D24A, which is using a switched 0.5mΩ sense element with a measurement range of -20A to +64A to report current.  The -1.18 - -1.4A error is the residual offset error remaining after our factory trim.  This is expected from the TPS546D24A and is covered in the electrical specifications table in it's datasheet.

    Gajendiran A said:
    why the different outputs (0.8V,0.9V,0.5V) has different offset current with 0.8V is 1.18A,0.9V is 1.16A and 0.5V is 1.4A?

    The TPS546D24A is measuring the peak inductor current 100-150ns after the turn-on of the low-side FET and 100-150ns before the turn-off of the low-side FET, then averaging those two values to determine the average inductor current.  The precise timing of those two samples coupled with the inductor ripple current can create a small dependence between the inductor ripple current (and thus duty cycle) and the measurement offset.