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August 31, 2011
Uh, so I just received mine a few days ago. I have a baffling, problem here. I was puttering around and forgot to connect Vcc, but did connect my 8V motor voltage, set standby to high, and applied my PWM signal. It turned on without Vcc and it seems to work normally (I think)!!
Vcc voltage seems to be about 1 volt less that whatever voltage is input to the PWM input voltage. It does not seem to change with motor voltage I can even power an LED off the Vcc pin, but some of the input waveform makes it through.
Anyone know if that is “normal”?? I don’t know if something is damaged inside the IC, or if it is behaving normally. It seems rather odd that Vcc does not need to be connected and can output a current.
Update: Controllerface (4 years ago) and c-scott (2 years ago) addressed this (see way below), It seems like I should at least put a diode in-line with Vcc and power Vcc first. I still don’t really understand why, or if I can just forget about powering Vcc. c-scott mentioned the possibility of an internal diode at Vcc and I did notice the driver heated up a lot if I actually connected Vcc to my circuit (AFTER connecting VM). Still confused….
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