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TPS61178: Boost Convert works fine with DC load, but fails when driving motor

Khoi Ly
Prodigy 240 points
Part Number: TPS61178
Other Parts Discussed in Thread: DRV8833

Dear TI,

I have a baffling situation that I don't fully understand where I did wrong of I have failed to consider. At the moment, I have a TPS61178 with LI-PO (3.7-4.1V) as input and my output is 5V.

I use this boost converter to drive a motor driver DRV8833 also from TI. The motor driver connects to two stepper motors in parallel (front and rear motors)  since I want the two motors to run sychronized and reduced footprint. 

I have tested and confirmed that the DRV8833 can drive two stepper motors in parallel with bench-top supply as input. However, the TPS61178 has significantly voltage drops at output (no longer regulating at 5V but 3.7 V instead).

I tested the TPS61178 with a constant load 8.6 Ohm resistor and, and I saw that the output voltage remains steady at 5V, resulting 580 mA of current output.

here is the Schematics and I am curious what you think. Please ignore the radio module. Only the TPS61178, the antagonistic valve uC, and the valve driver are installed.

Thank you very much and I look forward to hearing from you

Khoi

  • +1
    TI__Genius 12765 points

    Hi Khoi,

    thank you for reaching out.

    here are two approaches:

    1. As far as I know, the motor current is a sinusoidal one and the peak may be high.

    Could you have a test of the current waveform when using an external power supply with 5V?

    We need check the max output current needed.

    2. Could you provide the detail of inductor and PMOS? 

    They need to qualify for the max output current.

    Please connect me if you have any questions.

    Best Regards,

    Fergus

  • 0 in reply to Fergus He
    Prodigy 240 points

    Hi Fergus,

    Thank you very much for your reply. I have found out the issue to be the connecting wire between the power supply and the boost converter. When I tested it with the battery, the system works properly.

    Thank you for your time again,

    Khoi Ly