SLVUA41E
11
These next registers should be tuned for a particular system:
ADVANCE
– This adjusts the timing shift between when the DRV8308 receives Hall signals and
commutation. While a motor is running, ADVANCE can be modified in realtime (if
AUTOADV is disabled), and you will instantly see the difference in power supply
current. Lower current is generally better, but flutter performance can be a tradeoff.
LOOPGAIN
– This gain primarily affects max RPM, max torque, and startup speed overshoot. If
it’s too low, the motor won’t spin up to the commanded RPM, or the torque
capability may be limited. If it’s too high, motor speed will initially overshoot.
SPDGAIN
– This gain affects how aggressively error is compensated. If it’s too high, speed will
oscillate around the target speed
. If it’s too low, flutter may be higher.
FILK1
– Sets the Pole1 frequency.
FILK2
– Sets the Zero1 frequency.
COMK1
– Sets the Pole2 frequency.
COMK2
– Sets the Zero2 frequency.
3.2 Tuning process
Tuning a motor system is a trial-and-error process. The following steps are a general guide. The GUI
loads with default register values that attempt to have reasonable filter settings.
Step 1:
Use the first tab to run in PWM mode. You might need to try different wire connections and
HALLPOL to get your motor to consistently spin. After that, while spinning change ADVANCE and find
the value that causes the lowest power supply current and audible motor noise. Then stop the motor
by bringing ENABLE low.
Step 2:
Determine the appropriate clock frequency, f
CLKIN
(see
Select the third GUI tab, and:
Set AG_SETPT closest to your f
CLKIN
.
Set MOD120 to 3970
Set SPEED to 4000
Turn on the clock, and start the motor with ENABLE.
If the motor spins very roughly,
Try reducing or increasing f
CLKIN
to find a working case as a baseline reference.
Try changing the filters (FILK1/FILK2/COMK1/COMK2) with different combinations in
increments of 150. Spend some time to find good values.
Try increasing SPDGAIN and LOOPGAIN.
Step 3:
By now, the motor should spin smoothly, but the frequency of the signal on FGOUT might not
match f
CLKIN
. If the two frequencies don’t match, speed is not locked. Many times that can be fixed by
increasing LOOPGAIN or SPEED.
