SLVSC79D June 2014 – November 2020 DRV8801A-Q1
The idea behind placing multiple 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 6.
N is the number of 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 devices would be required to safely meet the needs of the system.