Datasheet

TMC220X, TMC222X DATASHEET (Rev. 1.02 / 2017-MAY-16) 52
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9 Motor Current Control
The basic motor current is set by the resistance of the sense resistors. Several possibilities allow
scaling down motor current, e.g. to adapt for different motors, or to reduce motor current in standstill
or low load situations.
METHODS FOR SCALING MOTOR CURRENT
Method
Parameters
Range
Primary Use
Pin VREF
voltage
(chapter 9.1)
VREF input scales
IRUN and IHOLD.
Can be disabled by
GCONF.i_scale_analog
2.5V: 100% …
0.5V: 20%
>2.5V or open: 100%
<0.5V: not recommended
- Fine tuning of motor current
to fit the motor type
- Manual tuning via poti
- Delayed or soft power-up
- Standstill current reduction
(preferred only with
spreadCycle)
Pin ENN
Disable / enable
driver stage
0: Motor enable
1: Motor disable
- Disable motor to allow
freewheeling
Pin PDN_UART
Disable / enable
standstill current
reduction to IHOLD
0: Standstill current
reduction enabled.
1: Disable
- Enable current reduction to
reduce heat up in stand still
OTP memory
OTP_IHOLD,
OTP_IHOLDDELAY
9% to 78% standby
current.
Reduction in about
300ms to 2.5s
- Program current reduction to
fit application for highest
efficiency and lowest heat up
OTP memory
otp_internalRsense
0: Use sense resistors
1: Internal resistors
- Save two sense resistors on
BOM, set current by single
inexpensive 0603 resistor.
UART interface
IHOLD_IRUN
TPOWERDOWN
OTP
IRUN, IHOLD:
1/32 to 32/32 of full
scale current.
- Fine programming of run and
hold (stand still) current
- Change IRUN for situation
specific motor current
- Set OTP options
UART interface
CHOPCONF.vsense
flag
0: Normal, most robust
1: Reduced voltage level
- Set vsense for half power
dissipation in sense resistor to
use smaller 0.25W resistors.
Select the sense resistor to deliver enough current for the motor at full current scale (VREF=2.5V). This
is the default current scaling (IRUN = 31).
STANDALONE MODE RMS RUN CURRENT CALCULATION:






 








IRUN and IHOLD allow for scaling of the actual current scale (CS) from 1/32 to 32/32 when using UART
interface, or via automatic standstill current reduction:
RMS CURRENT CALCULATION WITH UART CONTROL OPTIONS OR HOLD CURRENT SETTING:



  






 




CS is the current scale setting as set by the IHOLD and IRUN.
V
FS
is the full scale voltage as determined by vsense control bit (please refer to electrical
characteristics, V
SRTL
and V
SRTH
). Default is 325mV.
With analog scaling of V
FS
(I_scale_analog=1, default), the resulting voltage V
FS
‘ is calculated by: