I am working with a Pololu Dual VNH5019 Motor Driver. I want to configure it so that the motor 1 driver is the top of a half bridge and of course motor 2 is the other half.
I have Aout1 tied to Bout1 and these tied to one end of the load. the other end of the load is tied to Aout2 and Bout2
According to your datasheet the PWM input turns the LS on and off in all cases
If I set
INA1 = INB1 = on
this should turn LSA1 = LSB1 = OFF except when PWM1 is on, which would short motor driver 1 ???!!!
On the other hand, logically, I should have INA2 = INB2 = OFF, which would allow current to flow through HSA1 and HSB1 thru the load and into LSA2/LSB2 - right?
PWM2 shoudl have no effect since LSA2 = LSB2 = ON already
Please clarify how to implement in SW/HW - thanks
It sounds like you might be trying to connect the outputs of the motor drivers to drive a single motor. If so, you can find instructions and code for doing so in the “Using the Driver in Single-Channel Mode” section of the dual VNH5019 motor driver shield user’s guide.
I had already implemented the just of what is found in the user guide for single motor op but I used diff pins cause I needed the pins the example used. I have the same behavior as the truth table but I don’t like it that my outputs are hanging out at the 12v rail until the pwm goes high and the low side of the respective motor driver gets pulled to ground by turning both(?) Sides of the low side on. I’d rather have the output pins at ground and pull the high side of one side up to the rail upon pwm high
Also, in normal operation on any one vnh5019 it must be that Ina high must drive the high side of side A on and the the low side of side B on and at the same time insure ghat the high side of Side B is off and the low side of side A is off - else u’d short out. This I assume is internally logic controlled. So how come when u tie Ina inb together I don’t short the thing out???
When looking into your question, we realized that the truth table in the Using the Driver in Single-Channel Mode section of the VNH5019 shield’s user’s guide was incorrect. We have updated it to correctly show how the combined driver operates when the PWM input is held low.
Unfortunately, that is the way that the VNH5019 works. There is no way to get the outputs to alternate between drive and brake low when applying PWM signals to the PWM pin. However, if your system has longer intervals in which the motor should be stopped, you could bring INA and INB low and the PWM pin high to get OUTA and OUTB to both go low.
To prevent a short in an H-bridge, it is only necessary to make sure that the high-side MOSFET and low-side MOSFET on one side of the H-bridge are not on at the same time. When using a single VNH5019 driver each IN pin controls either the left or right half of the H-bridge independently of the other half, so as long as you don’t short the outputs, there is nothing to worry about. When you do short the outputs, you have to make sure that INA and INB are not trying to make the two output pins do different things.