Datasheet

TMC220X, TMC222X DATASHEET (Rev. 1.02 / 2017-MAY-16) 35
www.trinamic.com
0X70: PWMCONF – VOLTAGE MODE PWM STEALTHCHOP
Bit
Name
Function
Comment
16
pwm_freq0
selection
%01: f
PWM
=2/683 f
CLK
%10: f
PWM
=2/512 f
CLK
%11: f
PWM
=2/410 f
CLK
15
PWM_
GRAD
User defined amplitude
gradient
Velocity dependent gradient for PWM amplitude:
PWM_GRAD * 256 / TSTEP
This value is added to PWM_AMPL to compensate for
the velocity-dependent motor back-EMF.
With automatic scaling (pwm_autoscale=1) the value is
used for first initialization, only. Set PWM_GRAD to the
application specific value (it can be read out from
PWM_GRAD_AUTO) to speed up the automatic tuning
process. An approximate value can be stored to OTP by
programming OTP_PWM_GRAD.
14
13
12
11
10
9
8
7
PWM_
OFS
User defined amplitude
(offset)
User defined PWM amplitude offset (0-255) related to full
motor current (CS_ACTUAL=31) in stand still.
(Reset default=36)
When using automatic scaling (pwm_autoscale=1) the
value is used for initialization, only. The autoscale
function starts with PWM_SCALE_AUTO=PWM_OFS and
finds the required offset to yield the target current
automatically.
PWM_OFS = 0 will disable scaling down motor current
below a motor specific lower measurement threshold.
This setting should only be used under certain
conditions, i.e. when the power supply voltage can vary
up and down by a factor of two or more. It prevents
the motor going out of regulation, but it also prevents
power down below the regulation limit.
PWM_OFS > 0 allows automatic scaling to low PWM duty
cycles even below the lower regulation threshold. This
allows low (standstill) current settings based on the
actual (hold) current scale (register IHOLD_IRUN).
6
5
4
3
2
1
0