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DCC-EX / EX-MotorShield8874

Design files for the open source 5A Motor Shield
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Inrush current triggers fault #4

Open higaski opened 9 months ago

higaski commented 9 months ago

Hello

Out of curiosity, have you ever fixed the issue described in the e2e forum here: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1249338/drv8874-unrush-current-trippling-fault-due-to-capacitance-of-circuit

There is an accepted answer (green border around a post?) which mentions to put the IMODE pin into STATE Quad-Level 2 (basically adding 20k to GND), but from how I understand the datasheet that wouldn't really fix things and an overcurrent fault would still occur.

I'm thinking about putting a 1uH // 2R filter on the output stage to solve this.

pmantoine commented 5 months ago

We have not tried the 1uH/2R filter... we instead switch briefly to high frequency PWM mode in software to handle in-rush, then switch back to DCC mode. This appears to work. Have you tried the 1uH/2R solution?

higaski commented 5 months ago

No, I'm no longer using this device.

crosland commented 1 month ago

we instead switch briefly to high frequency PWM mode in software to handle in-rush, then switch back to DCC mode. This appears to work.

Does this mean the output is not DCC during startup?

pmantoine commented 1 month ago

we instead switch briefly to high frequency PWM mode in software to handle in-rush, then switch back to DCC mode. This appears to work.

Does this mean the output is not DCC during startup?

It is DCC on startup, and only switches to PWM if a short is detected at the point that particular output channel is turned on by software, and then only very briefly, sufficient to charge capacitors causing the in-rush issue in the first place.