Datasheet

TMC2209 DATASHEET (Rev. 1.03 / 2019-JUN-26) 8
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1.7 Automatic Standstill Power Down
An automatic current reduction drastically reduces application power dissipation and cooling
requirements. Per default, the stand still current reduction is enabled by pulling PDN_UART input to
GND. It reduces standstill power dissipation to less than 33% by going to slightly more than half of
the run current.
Modify stand still current, delay time and decay via UART, or pre-programmed via internal OTP.
Automatic freewheeling and passive motor braking are provided as an option for stand still. Passive
braking reduces motor standstill power consumption to zero, while still providing effective
dampening and braking!
t
CURRENT
TPOWERDOWN
power down
delay time
RMS motor current trace with pin PDN=0
IHOLD
IRUN
IHOLDDELAY
power down
ramp time
STEP
Figure 1.4 Automatic Motor Current Power Down
1.8 Index Output
The index output gives one pulse per electrical rotation, i.e. one pulse per each four fullsteps. It
shows the internal sequencer microstep 0 position (MSTEP near 0). This is the power on position. In
combination with a mechanical home switch, a more precise homing is enabled.
1.9 Precise clock generator and CLK input
The TMC2209 provides a factory trimmed internal clock generator for precise chopper frequency and
performance. However, an optional external clock input is available for cases, where quartz precision
is desired, or where a lower or higher frequency is required. For safety, the clock input features
timeout detection, and switches back to internal clock upon fail of the external source.