TMC2041 DATASHEET (Rev. 1.02 / 2017-MAY-16)
13
Well-regulated, stable
supply, better than +-5%
+5V
VSA
5V Voltage
regulator
5VOUT
4.7µ
10R
VCC
470n
Figure 3.4 Using an external 5V supply to bypass internal regulator
3.5 Optimizing Analog Precision
The 5VOUT pin is used as an analog reference for operation of the TMC2041. Performance will degrade
when there is voltage ripple on this pin. Most of the high frequency ripple in a TMC2041 design
results from the operation of the internal digital logic. The digital logic switches with each edge of
the clock signal. Further, ripple results from operation of the charge pump, which operates with
roughly 1MHz and draws current from the VCC pin. In order to keep this ripple as low as possible, an
additional filtering capacitor can be put directly next to the VCC pin with vias to the GND plane giving
a short connection to the digital GND pins (pin 6 and pin 34). Analog performance is best, when this
ripple is kept away from the analog supply pin 5VOUT, using an additional series resistor of 2.2Ω. The
voltage drop on this resistor will be roughly 100mV (IVCC * R).
22n
+VM
VCP
charge pump
100n
VSA
5V Voltage
5VOUT
GNDA
regulator
100n
4.7µ
2R2
VCC
470n
Figure 3.5 RC-Filter on VCC for reduced ripple
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. 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 might be varied between 100pF
and 1nF. The capacitors also dampen high frequency noise injected from digital parts of the circuit
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 against ESD voltage.
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