Embedded World: Trinamic chooses Risc-V for intelligent motor driver chip

Dubbed Rocinante (named from both Don Quixote and The Expanse, according to the firm), it is claimed to be the first motor driver with a Risc-V core – the MCU will run the application layer, providing a user interface or executing bus protocols, for example.

“Embedding powerful processors into motor controllers gives us a new degree of freedom and enables features that will be indispensable in the future – for example condition monitoring and predictive maintenance,” said company founder and CEO Michael Randt.

This said, “the motion control part happens completely in the hardware part of the chip”, company marketing manager Corné Bekkers told Electronics Weekly.

The 32bit core, 128kbyte eeprom-based non-volatile memory and 32kbyte sram allow it to handle field oriented control as well as high-level industrial protocols like CANopen or CANopen-FD. USB and CAN-FD interfaces, gate drivers for 2-phase or 3-phase motors, and switching regulators are included.

Currently three versions of Rocinante are planned, all operating from 5-30V – so none are general-purpose 3.3V MCUs. All require external power mosfets for a complete design (see diagram), all include an internal charge-pump to allow the bridges to be all-n-channel, and all can provide 1A gate drive.

• TMCR901-TA 6x gate drivers, 3x current sense, for brushless and brushed dc motors, and solenoids or voice coils in 7x7mm TQFP48
• TMCR902-TA 8x gate drivers, 2x current sense, for stepper and brushed dc motors, and solenoids or voice coils in 7x7mm TQFP48
• TMCR961-TA 8x gate drivers, 3x current sense, for brushless, stepper and brushed dc motors, and solenoids or voice coils in 10.5×6.5mm QFN76

Current sensing is through resistors in the bottom tail of the driver bridge or bridges

Pin-limiting in the small (7x7mm) package is the reason for having two options – trading a gate-drive pair for a current sense connection.

The large packages also adds interfaces – all get SPI, UART and CAN-FD, then the 961 also gets USB, QSPI and RTMI.

first engineering samples, together with evaluation boards (dubbed ‘Landungsbrücke’), motion control libraries and application code libraries are expected before Q4 this year.

Why Risc-V, and not the traditional Arm Cortex-M approach?

“It is open-source, so you don’t have the issue that the IP provider might get bought,” a Trinamic spokesman told Electronics Weekly at Embedded World – a reference to the purchase of formerly-independent Arm by SoftBank.

According to a Trinamic statemant: “Actuators, motors and mechanical components typically have a long product lifetime, so the longevity of the components is crucial for device manufacturers. The RISC-V ISA [instruction set] is stable and there are no obligations or license agreements which could prohibit long-term road-mapping, development or technology transfer.”

But Risc-V doesn’t have much of an eco-system?

“The eco-system is evolving and there are promising companies working on it,” said the spokesman. ” There are some things missing, but there is a community to discuss things with.”

He went on to point out that a new way of working is emerging – a more collegiate approach – Trinamic would not normally discuss new products so early (Rocinante is due out later in 2019), but with an open source community, adopters of Risc-V are going public to allow open conversations with other Risc-V users.