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TIDM-DC-DC-BUCK: The detected current value is inconsistent with the actual value

Green Deng
Expert 4490 points
Part Number: TIDM-DC-DC-BUCK

Dear team:

LAUNCHXL-F28379D & TIDM-DC-DC-BUCK

When one of my customers runs to lab 2 & Lab 4 without any load connection, the current of 0.19a is detected by the development board in the expressions window of CCS.

He would like to know where the current might come from?

  • 0
    TI__Expert 5985 points

    Hi Green,

    On the schematic, there is a dummy resistor load on the board (PR1) of 7.5 Ohm. With the ~ 2V output voltage, it makes sense to have 0.2-0.3 A of output current on the board.

    Best regards,

    Han

  • 0 in reply to Han Zhang6
    TI__Expert 4490 points

    Hi Han:

    Strangely, my client said that he had removed both the 7.5 ohm virtual resistor (PR1) and the adjustable resistor (PR2), but still had 0.2A current. This made him very confused.

  • +1 in reply to Green Deng
    TI__Guru 62975 points

    Green,

    There are a few things that should be kept in mind:

    1. The ILFB current feedback signal is very AC in nature and should not be considered to be the steady-state DC current; the value shown in the Expression Window represents the instantaneous current at a single point in the AC cycle
    2. The synchronous buck implementation will provide a current path from Vout to GND through the low-side FET during the off-time of the duty cycle so periodic current flow is expected

    -Tommy