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Using the LM2588 to drive a stepper motor chopper drive

Peter Wilson60
Prodigy 60 points
Other Parts Discussed in Thread: LM2588

I am using a LM2588 boost regulator to step up 7.2V to 24V to drive a stepper motor with an A4988 chopper drive.

When I run the chopper drive off of  a 24V power supply, everything runs great: I get dead smooth operation at up to 10,000 steps/sec. However, when I switch to the boost regulator, my stepper motor fails. Even at very low step rates (1000 steps/sec) my motor behaves as if it is getting very poorly timed step pulses: it spins, but when I am holding it, it jumps around in my hand, and it skips steps.  Placing a small (0.047uF) ceramic capacitor across the output of the regulator and another across the input of the driver board seems to help with this, but it still skips every 1-2s. This skip is, however, fairly regular, which makes me suspect that there may be a problem with the driver PWM and the boost regulator pulses temporarily synchronizing (I do not have access to an oscilloscope to verify this).

I am watching the voltage output by the regulator at all times, and it stays at a rock-solid 24V. As I have left the frequency adjust pin open, it has a switching frequency of 100Khz. 

Thanks for any advice you can provide.

  • 0
    TI__Guru 72545 points

    Without a 'scope it may be difficult to troubleshoot.  Can you send your schematic and PCB layout?

    What current do you need from the 24V?

    Keep in mind that the 7.2V input supply will require at least 24/7.2 = 3.3x more current than the motor requires; make sure you have enough power from your input supply.