Part Number: DRV8308
Hi,
I have the DRV8308 running my 4 pole,24 volt motor with a maximum RPM of 10000. I have the following set:
- PWM frequency = 25 KHZ and duty cycle of 50%
- Set for Clock Frequency Mode.
- I've set the registers as follows (Register dump from my custom board):
- MCR00[0xD901]
- MCR01[0x0000]
- MCR02[0x03B4]
- MCR03[0x6F82]
- MCR04[0x0340]
- MCR05[0x3000]
- MCR06[0x0481]
- MCR07[0x03BA]
- MCR08[0x012C]
- MCR09[0x0250]
- MCR0A[0x0000]
- MCR0B[0x0168]
- Fault Register reads on power up:
- MCR2A[0x0018]
I have both LOOPGAINand SPEEDGAINSet to 0for testing.
I am running the motor at 3600 RPM. I have to set the SPEED Register to 360 to get the motor RPM to 3600.
The motor runs smoothly. @90 mA.
The Tach output is bouncing between 3549 and 3584 RPMs ( I obviously need to tune it).
I have my own diagnostics window for modifying the registers, setting direction, applying the brake, enable, etc...
I am confused about how Fclkin and the Tach could ever be the same.
Is Fclkin supposed to be the PWM output from the ATMEGA 2560 timer? PWM frequency is 25 KHZ. How would that match 3600 RPM?
I'm going by the tuning guide to set these things up and trying to calculate the LOOPGAIN and SPEEDGAIN.
Can you shed some light on this?
Thank you,
Reif Heck
Finna Sensors
