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Original question:

TPS62933: Inductor ripple current

TPS62933: current sense resistor Iout large ripples

Steven Wang
Prodigy 230 points
Part Number: TPS62933
Other Parts Discussed in Thread: INA180

I am utilizing the INA180 for monitoring DCDC current. The INA180 amplifies the voltage across the current sensing resistor, presenting a sine wave pattern as observed on the oscilloscope. Consequently, despite a stable output current and voltage, my STM32 ADC records a sine wave pattern in the current sense value. Vin = 12VDC, Vout is stable, about 250mV ripple. I don't want to place the current sense resistor after feedback path because it will cause some voltage drop at the load. Is there a design issue causes Iout ripple? Thanks 

  • +1
    TI__Expert 5470 points

    Hi Steven,

    In fact, what you measured is inductor current but not output current.

    I understand that you want to place FB divider after current sense resistor to compensate the I*R drop. But at least the output capacitor needs to be placed before the current sense resistor.

    But this inductor current ripple frequency seems quite low. The frequency of inductor current ripple should be switching frequency. As you selected 1.2MHz mode, I'm not sure if this is real switching frequency or that's because the current sensing is limited by amplifier & STM32 bandwidth.

    Maybe you could measure the SW waveform to check the real switching frequency.

    Thanks,

    Andrew