The idea behind placing multiple DRV8800/01 devices in parallel is to increase maximum drive current. At first glance, it may seem that the new increased ITRIP setting is given by Equation 8.
N is the number of DRV8800/01 devices connected in parallel.
ITRIP is the individual ITRIP value per device.
However, although in theory accurate, due to tolerances in internal SENSE amplifier/comparator circuitry, the system ITRIP should be expected to be less than the addition of all the individual ITRIP. 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 DRV8800/01 devices would be required to meet the safety needs of the system.