EtherCAT P (EtherCAT + Power) is an extension of EtherCAT - a real-time communication protocol standard based on 100Mbps standard Ethernet. EtherCAT P uses the same four wires of standard EtherCAT for distribution of power in addition to data. Low-pass filters (inductivities) and high-pass filters (capacitors) are used to separate power and signals at the slave device. Two isolated supply voltages Us (system and sensor supply) and Up (peripheral and actor supply) with 24V / 3A each are available with EtherCAT P. A special M8 connector (M-code) and a red+black colored cable clearly distinguishes EtherCAT P connections from standard EtherCAT connections.
In an initial attempt to support EtherCAT P with Trinamic’s EtherCAT slave controller ICs, the TMC8462 EtherCAT P reference design has been developed. It features the TMC8462 EtherCAT slave controller (ESC) with two integrated PHYs for building a standard EtherCAT slave device supporting daisy-chain topology. It is part of the TRINAMIC Eval board concept and offers two 44 pin double row headers. One is used for connection to the processor board (Landungsbrücke) and the second one for attaching further Eval boards e.g. controller / driver boards passing through the control signals to the processor board.
Next to the TMC8462, related passive components incl. mentioned low-pass and high pass filters for separation of power and data and standard Ethernet 100MBit/s signal transformers are included on-board. The board offers two EtherCAT P M8 connectors for EtherCAT LINK IN and LINK OUT connection. Furthermore, a switching DC/DC converter has been integrated. This way, two switching DC/DC converters are available including the one on the Landungsbrücke – one for each EtherCAT P power supply Us and Up. Nevertheless, please note: these two converters and the voltages are not isolated from each other as they share a common ground connection. This may simplify laboratory setups and testing, after which the concept has to be adapted to the latest EtherCAT P standard when implementing the design in your application.
An example of a stepper motor controller + driver unit with EtherCAT P interface with isolation between system and driver part is shown as block diagram above. For the motion control part, the advanced TMC4361 motion controller has been selected while for the driver stage the TMC5130 with integrated MOSFET driver stage is used.
This setup is able to support stepper motors with 1-1.5A RMS motor coil current with optional encoder feedback and support for closed-loop operation. While the motion controller, processor and interface part is powered via Us, the driver part is connected to Up. This way, all motion controller related data, including current step position counter and optional encoder feedback, are retained (and even updated in case of the encoder) while Up is switched off (driver stage disabled) and Us is still available and valid. For isolation, an SPI connection between driver and motion controller has been selected in this design. Standard highly integrated single SPI isolator ICs may be used for this purpose.