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ULN2003A: Voltage spikes from stepper motor

Part Number: ULN2003A

Hi all,

In our basic stepper motor board we are using the ULN2003 to perform little steps with a small stepper motor. Motor runs at 5V total ~200mA for only the first 4 channels (see schematic below), 5,6,7 are floating (input grounded). Runs on PWM signals from 3.3V MCU. This works perfectly fine.

However we are observing some voltage peaks in our power supply (induced emf?) then the motor is performing/or done with a step. When running from steady increases to 5.8V! This is unwanted because of other components on the same 5V power rail. I prefer the 5V-line to be very stable.

Regarding the datasheet there is no need for additional diodes. I have tried to add an additional, big aluminum electrolytic capacitor from COM to GND. But no real effect.

Please advice!

Thanks in advance!
- Sander