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MeltManBob
It sounds like what you are saying about reaching the max current is the driver is capable of reaching voltages higher than the supply voltage in order to dictate the current limit which I've also read in the data sheet but I wasn't 100% certain about. This makes me think that the supply voltage dictates how high the driver can pump the voltage and/or how fast it can pump it because even if the driver can get a higher voltage to reach the current limit there has to be some limitation as to how high a voltage it can produce and consequently how fast it can get to the current limit.
So how do I find out what the maximum voltage is that can be produced by the driver?
No, the stepper driver does not boost the voltage, it does not produce bigger voltages than its input. Sry if i said something that could be interpreted as such. If there is something like a charge pump in the datasheet, that is to produce voltage for the gates of high side mosfets, thats all. In the case the high side mosfets are n-channel, to drive them it they require a gate current higher than the voltage they sit at, so if they are on the 12v line, they need like 17v plus gates to start conducting. Allegro use n-mosfets for high side, other chip manufacturers may use p-channel for high side and hence they do not need charge pump because p-channel will conduct with gate less than 12v. If other voltages appear on the coils, its from inductive spikes and not because the stepper driver increases the voltage on the coil. Otherwise the voltage that is supplied to the coil is the same with input voltage, which does have a maximum of 32-35-40v or something like that, yes its in datasheet.
No, the pulse signal on time has no significance whatsoever. On the step line nothing matters, not the frequency, not the duty cycle, not the pulse duration. You will see in datasheet something like step minimum pulse width, but that is just monitoring to make sure the step signal was valid and not an occasional spike. Other than that the pulse width is not processes further, if pulse width would mean anything else it would be dc servo not stepper. I have said all this like many times.Quote
MeltManBob
I'm assuming that the driver pays attention to how long the pulse signal on time is and then multiplies it by 2 to determine the time frame that it needs to turn on the current and then off based on the decay mode.