Datasheet
TMC220X, TMC222X DATASHEET (Rev. 1.02 / 2017-MAY-16) 18
www.trinamic.com
critical for the tiny QFN 5mm x 5mm package at or above 1A RMS motor current for increased periods
of time. Keep in mind that resistive power dissipation raises with the square of the motor current. On
the other hand, this means that a small reduction of motor current significantly saves heat dissipation
and energy.
Pay special attention to good thermal properties of your PCB layout, when going for 1A RMS current
or more.
An effect which might be perceived at medium motor velocities and motor sine wave peak currents
above roughly 1.4A peak is a slight sine distortion of the current wave when using spreadCycle. It
results from an increasing negative impact of parasitic internal diode conduction, which in turn
negatively influences the duration of the fast decay cycle of the spreadCycle chopper. This is, because
the current measurement does not see the full coil current during this phase of the sine wave,
because an increasing part of the current flows directly from the power MOSFETs’ drain to GND and
does not flow through the sense resistor. This effect with most motors does not negatively influence
the smoothness of operation, as it does not impact the critical current zero transition. The effect does
not occur with stealthChop.
3.6 Driver Protection and EME Circuitry
Some applications have to cope with ESD events caused by motor operation or external influence.
Despite ESD circuitry within the driver chips, ESD events occurring during operation can cause a reset
or even a destruction of the motor driver, depending on their energy. Especially plastic housings and
belt drive systems tend to cause ESD events of several kV. It is best practice to avoid ESD events by
attaching all conductive parts, especially the motors themselves to PCB ground, or to apply electrically
conductive plastic parts. In addition, the driver can be protected up to a certain degree against ESD
events or live plugging / pulling the motor, which also causes high voltages and high currents into
the motor connector terminals. A simple scheme uses capacitors at the driver outputs to reduce the
dV/dt caused by ESD events. Larger capacitors will bring more benefit concerning ESD suppression,
but cause additional current flow in each chopper cycle, and thus increase driver power dissipation,
especially at high supply voltages. The values shown are example values – they may be varied
between 100pF and 1nF. The capacitors also dampen high frequency noise injected from digital parts
of the application PCB circuitry and thus reduce electromagnetic emission. A more elaborate scheme
uses LC filters to de-couple the driver outputs from the motor connector. Varistors in between of the
coil terminals eliminate coil overvoltage caused by live plugging. Optionally protect all outputs by a
varistor to GND against ESD voltage.
Full Bridge A
Full Bridge B
stepper
motor
N
S
OA1
OA2
OB1
OB2
Driver
470pF
100V
470pF
100V
470pF
100V
470pF
100V
Full Bridge A
Full Bridge B
stepper
motor
N
S
OA1
OA2
OB1
OB2
Driver
470pF
100V
470pF
100V
50Ohm @
100MHz
50Ohm @
100MHz
50Ohm @
100MHz
50Ohm @
100MHz
V1
V2
Fit varistors to supply voltage
rating. SMD inductivities
conduct full motor coil
current.
470pF
100V
470pF
100V
Varistors V1 and V2 protect
against inductive motor coil
overvoltage.
V1A, V1B, V2A, V2B:
Optional position for varistors
in case of heavy ESD events.
BRB
R
SA
BRA
100nF
16V
R
SB
100nF
16V
V1A
V1B
V2A
V2B
Figure 3.4 Simple ESD enhancement and more elaborate motor output protection