I'm using a TB6612FNG driver to control a DC motor (only a single motor in the system so only using one of the two drivers on the chip). The motor is a 12V 37D type, very large gear ratio, fairly slow output rotation, very high torque, but for a 37D the stall current is low at only 0.5A.
When I stop the motor by sending both inputs of the H bridge low the TB6612FNg sends the outputs to a high impedance state and the motor takes several seconds to stop, when the motor is moving a high torque load this takes even longer (angular momentum of load and gearbox keeping going).
I need a faster stop, so I'm considering using the short brake mode of the driver, for various reasons the rest of my circuitry means it is easier to send the PWM input low for this rather than send both direction inputs high. I don't know whether the driver can cope with doing this for this motor though.
I have no idea what kind of currents and voltages might occur due to the motor's inductance (I have no easy way to mesure this, and the motor datasheet doesn't say it) when it gets braked. I know the motor has a DC resistance somewhere below 39 Ohms (I attached a DC multimeter and the reading declined slowly, taking more than 30 seconds to drop by 0.1 Ohms by the time it was at 39 Ohms), but inductance may be messing with this reading, and I don't know how the brushes might have been sitting at the time I took the ohms measurement. Also for consideration, I suspect, must be that by moving a high momentum high torque load there will be substantial mechanical effects keeping trying to turn the shaft when braking occurs. Quite how these mechanical effects might affect the braking current I'm not sure.
The driver chip's datasheeet says nothing about how much braking current it is rated for, or for what time periods, it just talks about the continuous current under normal back or forward running conditions.
Is there a way to work this out, I know the chip has survived these brake currents in testing, but I also know that chips often survive beyond max ratings in a few tests, but then wear out fast if operated like this long term.
Thanks
P.S. On a related topic, I've heard PWM speed control is better done by alternating between short brake and running in your desired direction, rather than alternating running and coasting, can anyone explain why this is? I'd have thought that by not repeatedly shorting the motor you'd get better torque at any speed by letting it coast?