TMC2225 DATASHEET (Rev. 1.15 / 2023-FEB-16)
49
9 Motor Current Control
The basic motor current is set by the resistance of the sense resistors. Several possibilities allow
scaling down motor current to adapt for different motors, or to reduce motor current in standstill or
low load situations.
METHODS FOR SCALING MOTOR CURRENT
Method
Pin VREF
voltage
(Chapter 9.1)
Parameters
VREF input scales
IRUN and IHOLD.
Can be disabled by
GCONF.i_scale_analog
Pin ENN
Pin PDN_UART
OTP memory
Disable / enable
driver stage
Disable / enable
standstill current
reduction to IHOLD
OTP_IHOLD,
OTP_IHOLDDELAY
OTP memory otp_internalRsense
UART interface IHOLD_IRUN
TPOWERDOWN
OTP
UART interface CHOPCONF.vsense
flag
Range
2.5V: 100% …
0.5V: 20%
>2.5V or open: 100%
<0.5V: not recommended
0: Motor enable
1: Motor disable
0: Standstill current
reduction enabled.
1: Disable
9% to 78% standby
current.
Reduction in about
300ms to 2.5s
0: Use sense resistors
1: Internal resistors
IRUN, IHOLD:
1/32 to 32/32 of full-
scale current.
0: Normal, most robust
1: Reduced voltage level
Primary Use
- 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)
- Disable motor to allow
freewheeling
- Enable current reduction to
reduce heat up in stand still
- Program current reduction to
fit application for highest
efficiency and lowest heat up
- Save two sense resistors on
BOM, set current by single
inexpensive 0603 resistor.
- Fine programming of run and
hold (stand still) current
- Change IRUN for situation
specific motor current
- Set OTP options
- 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:
������������������������
=
325������������
������������������������������������ + 30������Ω
∗
1
√2
∗
������������������������������
2.5������
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:
������������������������
=
������������ +
32
1
∗
������������������
������������������������������������ + 30������Ω
∗
1
√2
CS is the current scale setting as set by the IHOLD and IRUN.
VFS is the full-scale voltage as determined by vsense control bit (please refer to electrical
characteristics, VSRTL and VSRTH). Default is 325mV.
With analog scaling of VFS (I_scale_analog=1, default), the resulting voltage VFS‘ is calculated by:
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