Modern automotive power distribution in EVs features a section dedicated to the high-voltage power distribution, normally connecting the main battery voltage to: the traction motor, the OBC, the heater, the e-compressor, and the main DC-DC converter.
A section for the low-voltage power distribution that takes care of delivering the power from the output of the main DC-DC to the various car loads through the wire harness, is also available.
In a traditional low-voltage board-net topology, when replacing the “e-fuse box” inside the vehicle, the power distribution is composed of a main primary board connected via a power rail switch board (PRS) directly with the output of the high-voltage DC-DC.
This is the case with our STEVAL-PDUBV1. Based on this architecture, our system consists of a primary distribution unit (PDU) featuring several channels for the different points of load in the car.
The STEVAL-PDUBV1 serves as an automotive-intended primary power distribution unit, positioned closer to the loads, thereby reducing the total wire length within the zone control unit, with a maximum operating voltage of 28 V, featuring the latest STi2Fuse generation of e-fuses and p-channel companion chips for parking mode and low quiescent current applications.
All the devices on the board are automotive grade including the connectors and the discrete parts.
The board features two independent power rails with separate inputs. Each rail consists of 13 output channels with different current carrying capabilities, from 5 up to 200 A, leveraging STi2Fuse devices and ST F8 MOSFET technology.
Designed as an all-in-one unit to optimize space, the board protects primary circuits (such as preheating, electric steering, and body computers) and distributes DC-DC output power sourced from the main battery, and / or the auxiliary battery, and / or the engine, and / or the regenerative braking.
To replace the physical e-fuses, the PDU channels have been protected with high-side drivers integrating smart e-fuses with a current threshold configurable via SPI to block the channel current drain at a given certain level.
This generation of regenerable, configurable, and precise smart e-fuses replace standard discrete e-fuses. A key feature is STi2Fuse protection (ST proprietary I2t functionality), an intelligent circuit breaking mechanism designed to protect PCB traces, connectors, and wire harnesses from overheating, without impacting load transients such as inrush currents and capacitance charging.
The I2t curve parameters can be individually configured for each channel. The dissipated power is limited to a safe level, up to the point of thermal shutdown intervention.
The device enters a fail-safe mode in case of communication loss with the microcontroller, reset of digital memory, or watchdog monitoring time-out event. In fail-safe mode, the output can be directly controlled by dedicated, assignable direct inputs.
To meet the highest automotive safety standards, all e-fuse devices include a periodic watchdog operating within a defined time window.
The board also features the powerful ASIL-D SPC58NG84E7 chorus MCU, with 6 MB flash memory able to host large applications and configuration parameters.
The available communication interfaces are a CAN-FD channel, a 100 BASE-TX automotive Ethernet channel, and a UART communication port to be used with an external UART-to-USB converter.
The MCU power management in the STEVAL-PDUBV1 is managed by three different devices: two PMICs (SPSB081 and SPSA068) and an LDO (LDL40).
The board has a dedicated supply capacity for external 3.3 V loads. The whole system runs at 3.3 V.
The board comes with basic operating firmware (STSW-PDUB-UDS) implementing a CAN message responder coupled with ISO14229 (UDS) standard used for diagnostic purposes.
The software is preburned on the STEVAL-PDUBV1 board, and the same flash memory image can be downloaded from ST web page.
In the same zip file, we include the DBC file for the CAN messages. Future software extensions might include a complete GUI based on the UART port available on board.
Ethernet communication is available at the hardware level but reserved for future use at software level.
