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Part Number: DRV8884
DRV8884 is used for driving a stepper motor. The design parameters are,
1. RREF = 562K
2. TRQ = 1
3. DECAY = tied to DVDD (slow decay)
4. We use both 1/4 and 1/2 stepping modes in our design and two PWM frequency - 400Hz and 800Hz.
Theoretically, by using a 562k RREF resistor should result in 53mA max current when the motor is running (37.7mA RMS).When measured the max. current appears to be close to this - 60mA (there may be some error in the 562k resistor, the DRV8884 and the probe.)
But the measure data of motor current for the same motor but different hardware board, shows larger than 10% variation. Could you please suggest how to let the output current more stable?
The current measured in 30 boards are attached.
Motor drive current.xlsx
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In reply to uhtis:
Rick DuncanMotor Applications Team
In reply to Rick Duncan:
The testing is done at customer site and I have asked to share the waveforms.
Regarding the decay mode, the setting is slow decay. The DECAY pin is tied to 3.3V in design and we have not tried any other options.
Meanwhile, what all factors affect the output current stability?
Please see the waveforms attached.
Why the driving current of DRV8884 is not stable?
But even if we increase the full scale current, it may vary from board to board. Do you have any suggestion to make the drive current stable in all boards?
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