Need Help With Stepper Motor DriverTMC5240 LC Filter

[Ednet1]

Hello everyone,

I am using the Analog Devices TMC5240 to drive a Sanyo Denki Sanmotion SM2564C20B41P bipolar stepper motor specs 2A/phase, 2.1 Ω/phase & 11mH/phase. I will be powering the stepper with 24Vdc @ approx. 2A.

The data sheet (attached) for the Analog Devices TMC5240 stepper driver suggests that if using a high current that you should use an LC Filter between the driver & the stepper motor similiar to the image Attached.

The information they give to select the appropriate components is the wording below.

"A more elaborate scheme uses LC filters to decouple the driver outputs from the motor connector. Varistors V1 and V2
in between of the coil terminals eliminate coil overvoltage caused by live plugging. Optionally protect all outputs by a
varistor (V1A, V1B, V2A, V2B) against the ESD voltage. Fit the varistors to the supply voltage rating. The SMD
inductivities conduct full motor coil current and need to be selected accordingly."

Can anyone please help me in selecting the appropriate Inductors, varistors & capacitors for this LC filter?
Also has anyone used the Analog Devices TMC5240 stepper driver, I am hoping to control it with a Raspberry Pi 5 via SPI, I never used one of these drivers before. How do you go about connecting it to the RPI5?

 

[Harald Kapp]

Can anyone please help me in selecting the appropriate Inductors, varistors & capacitors for this LC filter?

The values for the inductors and capacitors are given in the schematic.
The inductors need to be able to carry >= 2 A without saturation. I suggest you select inductoirs with a minimum rated current of 4 A or higher to have some good safety margin.

The capacitors need to be able to withstand the 24 V plus potential overvoltage from switching the inductances. The next rated standard voltage is 25 V which is imho way too near to the 24 V operating voltage. Your capacitors should be rated 50 V or 63 V which are standard voltage ratings.

The varistors need to withstand the 24 V operating voltage without breakdown but should become conductive for overvoltages. Accounting for possible permanent overvoltage on the 24 V power supply, a good choice is a varistor rated for 30 V DC or higher. See this article for more detail (includes an example for 24 V ).

 

[Ednet1]

Hi Harold, thanks for getting back to me.
I am still confused with the values for the inductors, it says 50 Ohm@100MHz how do I calculate inductance(uH) for these inductors?

 

[Harald Kapp]

You could, using the equation [imath]Z = 2×Pi×f×L[/imath].
But that is not necessary. The "inductors" shown in fig. 41 in post #1are typically ferrites with defined loss to suppress EMC.
Go to the selection page of the distributor of your choice (e.g. this one). Select suitable filter parameters, e.g.:

• impedance between 40 Ohm and 60 Ohm (the 50 Ohm of the app note are for orientation. Give or take a few Ohm will not make a relevant difference.
• max. DC current >= 2.5 A - note that I applied 500 mA safety margin to your 2 A motor current to avoid saturation

Then you'll have to scan the resulting table and, it can't be avoided, look up the data in the datasheet. Here's an example:

 

[Ednet1]

Thanks Harald, you have been a great help. I put this question on several forums including Anolg Devices Engineer Zone and their support.You are the only person to respond, thanks again.
PS: I just realised I spelt your name incorrectly in my first reply, I do apoligise.