SWCU193 April 2023 CC2340R2 , CC2340R5 , CC2340R5-Q1
The LGPT can be used to drive a BLDC motor. Consider a BLDC motor with 3 half bridges, this requires three or more channels. In this scenario the 3 IOC and the 3 IOC complementary outputs of one LGPT are connected to a motor driver or directly to the half bridges. See Figure 10-15.
Here each half bridge is controlled by an IOC and IOC complementary pair, that is, PWM0 and PWM1 corresponds to IOC[0] and IOC_C[0], PWM2 and PWM3 to IOC[1] and IOC_C[1] and so on. To operate the motor in a basic fashion current is driven through two of the inductors at a time in a sequential pattern. This is done by switching the transistors in a distinct pattern, see Figure 10-16.
Notice that the high time of each transistor consists of a PWM signal (as illustrated in Q0). The duty cycle of the PWM signal corresponds to the current that is driven through the inductors and consequently the motor speed/load. The PWM can be generated as mentioned in Section 10.3.6.2. The software interactions needed to operate the motor (We assume Q0 is connected to IOC[0] and Q1 connected to IOC_C[0] etc.) are as follows:
SW operations:
Software needs a signal to determine when to change between the different phases, this can for example be done by an ADC measuring the back (EMF) Electromotive Force at the inactive inductor. Software can also change phases only on a ZERO interrupt from LGPT to ensure complete PWM pulses during phase changes.