MOSFET driver IC behaving weirdly

Hi!

I am using an MCP 14E9-E/P with my nano 33 BLE sense to control some micromotors. So in my head, this was about connecting the motors to the "OUT A" and "OUT B" pins of the MCP 14E9 and the "IN A" and "IN B" to analog outputs of the Arduino. Then I should be able to control the motor speed via PWM I thought.

What happens now is that the MOSFET behaves relatively randomly. When I touch the blank "IN A" contact for example sometimes it turns the motor on and it stays on after I let loose. Sometimes it turns off if I touch again. Sometimes it seems to randomly turn itself on?

VDD gets 3.3V from a lipo (regulated)
GND is connected
ENA and ENB are connected to VDD
OUTA and OUTB are connected to Chinese micromotors

It is not defective I tried two.
Datasheet of the IC: https://cdn-reichelt.de/documents/datenblatt/A200/MCP14E9-10-11.pdf

What did I not get about this IC?

Thank's in advance!

You set the Arduino pins as OUTPUT?

Are you trying to use non-PWM pins with analogWrite?

Do you have proper decoupling on the MCP14E9? I'd suggest 0.1uF and at least 10uF, both ceramic MLCC types within a few mm of the chips' supply pin.

I found the issue it seems to work now but I will have to have the PCB printed again so as we are at it rn: Why decoupling caps? And do I need pulldowns on the drains? It seems they are still floating when not getting a clear signal from the Arduino which can be bad for motor control.

  1. The chip datasheet clearly states the operating voltage range 4.5v to 18V. So, I question the desire to feed Vdd with 3.3V.
  2. The chip datasheet clearly shows Multiple decoupling capacitors in example diagrams... so why do you second guess the design engineers, If they say use decoupling capacitors, they often mean what they say... They are not getting kickbacks from Capacitor manufacturers.

Pull up or pull down the pins and this issue would resolve!