Tool/software:
Dear Ryan,
We are still using the DRV8873HPWPR(Q1) and we want to drive it by PWM (PH/IN2, pin 8) therefore two questions:
1. if we go to PWM is it than necessary to put the pin Mode (pin 3) to the VDD, because now it is connected to GND
2. what is the best PWM frequency to use
Best Regards,
Piet
Hi Piet,
Thank you for posting in this forum.
We are still using the DRV8873HPWPR(Q1) and we want to drive it by PWM (PH/IN2, pin 8) therefore two questions:
1. if we go to PWM is it than necessary to put the pin Mode (pin 3) to the VDD, because now it is connected to GND
Both PH/EN mode with MODE = GND and PWM mode MODE = HIGH can support PWM input control.
In PH/EN mode, MODE = GND, the EN/IN1 pin would be the enable control. This can be driven with a variable duty cycle fixed frequency PWM from 0 to 100 % duty cycle for BDC motor speed control. In this mode the motor direction will be determined by the PH/IN2 pin input. See Table-4 from the datasheet - shown below.
In PWM mode, MODE = HIGH the control scheme would be different. See Table-5 in the datasheet. When both IN1 and IN2 = 1 the motor would be in idle (slow decay / high-side brake). IN2 = 1, IN1 = PWM for one direction and IN1 = 1 and IN2 = PWM for the other direction. In this mode two separate PWM inputs are necessary one of each direction. From this standpoint PH/EN has the benefit that only one pin needs to be PWM input.
2. what is the best PWM frequency to use
Usually a 20 kHz PWM is used to keep it just above the audible frequency range. Some motors tend to produce louder audible noise depending on its construction, mounting and use case. Higher switching frequency increases switching losses hence affects efficiency. So PWM frequency is a trade off between audible noise and switching losses. Another factor is the EMI for EMC.
The DRV8873 can support up to 100 kHz PWM input. Thank you.
Regards, Murugavel
