The idea behind placing multiple devices in parallel is to increase maximum drive current. At first glance, it may seem that the new increased I_TRIP setting is given by Equation 8.

Equation 8.

Where:

N is the number of devices connected in parallel.

I_TRIP is the individual I_TRIP value per device.

However, although in theory accurate, due to tolerances in internal SENSE amplifier/comparator circuitry, the system I_TRIP should be expected to be less than the addition of all the individual I_TRIP. The reason for this is that as soon as one of the devices senses a current for which the H Bridge should be disabled, the remaining devices will end up having to conduct the same current but with less capacity. Therefore, remaining devices are expected to get disabled shortly after.

A good rule of thumb is to expect 90% of the theoretical maximum.

By way of example, if the system level requirements indicate that 6 A of current are required to meet the motion control requirements, then:

6 A = (2.8 A x 0.9)N

N = (6 A) / (2.8 A x 0.9)

N = 2.38

In this example, three devices would be required to safely meet the needs of the system.