Datasheet

TMC2209 DATASHEET (Rev. 1.03 / 2019-JUN-26) 51
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with V
VREF
the voltage on pin VREF in the range 0V to V
5VOUT
/2
Hint
For best precision of current setting, measure and fine tune the current in the application.
PARAMETERS FOR MOTOR CURRENT CONTROL
Parameter
Description
Setting
Comment
IRUN
Current scale when motor is running. Scales coil
current values as taken from the internal sine
wave table. For high precision motor operation,
work with a current scaling factor in the range 16
to 31, because scaling down the current values
reduces the effective microstep resolution by
making microsteps coarser.
0 … 31
scaling factor
1/32, 2/32, … 32/32
IRUN is full scale (setting
31) in standalone mode.
IHOLD
Identical to IRUN, but for motor in stand still.
IHOLD
DELAY
Allows smooth current reduction from run current
to hold current. IHOLDDELAY controls the number
of clock cycles for motor power down after
TPOWERDOWN in increments of 2^18 clocks:
0=instant power down, 1..15: Current reduction
delay per current step in multiple of 2^18 clocks.
Example: When using IRUN=31 and IHOLD=16, 15
current steps are required for hold current
reduction. A IHOLDDELAY setting of 4 thus results
in a power down time of 4*15*2^18 clock cycles,
i.e. roughly one second at 16MHz clock frequency.
0
instant IHOLD
1 … 15
1*2
18
… 15*2
18
clocks per current
decrement
TPOWER
DOWN
Sets the delay time from stand still (stst) detection
to motor current power down. Time range is
about 0 to 5.6 seconds.
0 … 255
0…((2^8)-1) * 2^18 t
CLK
A minimum setting of 2
is required to allow
automatic tuning of
PWM_OFFS_AUTO
vsense
Allows control of the sense resistor voltage range
for full scale current. The low voltage range
allows a reduction of sense resistor power
dissipation.
0
V
FS
= 0.32 V
1
V
FS
= 0.18 V
9.1 Analog Current Scaling VREF
When a high flexibility of the output current scaling is desired, the analog input of the driver can be
used for current control, rather than choosing a different set of sense resistors or scaling down the
run current via the interface using IRUN or IHOLD parameters. This way, a simple voltage divider
adapts a board to different motors.
VREF SCALES THE MOTOR CURRENT
The TMC2209 provides an internal reference voltage for current control, directly derived from the
5VOUT supply output. Alternatively, an external reference voltage can be used. This reference voltage
becomes scaled down for the chopper comparators. The chopper comparators compare the voltages
on BRA and BRB to the scaled reference voltage for current regulation. When I_scale_analog in GCONF
is enabled (default), the external voltage on VREF is amplified and filtered and becomes used as
reference voltage. A voltage of 2.5V (or any voltage between 2.5V and 5V) gives the same current