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System Basis Chips

The future is integrated

So-called System Basis Chips (SBC) increasingly substitutes CAN transceiver chips. Carmakers in particular are in favor of these highly integrated circuits.

The SBC combines a transceiver, voltage regulator, watchdog, driver, and switch (Photo: Infineon)

THE TREND IS CLEAR: ALL IN ONE IS THE GOAL. The automotive industry wants to reduce the number of components, in order to save space on the printed circuit boards. Discrete components have become a thing of the past. The future is integrated. Infineon (Germany), NXP (Netherlands), and other chipmakers offer CAN transceivers combined with other functions such as voltage regulator, fail-safe I/O, H-bridge driver, etc. Of course, LIN transceivers can be integrated as well. These SBCs are used in body, door, seat, climate, roof, and light control units, for example. One of the benefits is the reduction of current consumption due to the advanced power management and the optional partial networking when using transceivers with selective wake-up function.

A typical SBC family, like the TLE826x by Infineon, features one CAN transceiver and none or up to three LIN transceivers. They provide a low-dropout voltage regulator (LDO) for an external 5-V supply. The components offer low-power modes in order to support applications that are connected permanently to the battery. A wake-up from the low-power mode is possible via a message on the buses or via the bi-level sensitive monitoring/wake-up input as well as from the SPI command. Each wake-up source can be inhibited. The 16-bit SPI (serial peripheral interface) is used to control and monitor the SBC by a micro-controller.

The SBCs are available in different versions with and without LIN transceivers (Photo: Infineon)

NXP and Freescale (USA) have similar SBCs in their portfolios (e.g. UJA113x or UJA107x families resp. MC33742). These product lines might be merged, when the acquisition of Freescale by NXP is finalized by end of this year. The UJA107x chips are available for 3,3-V and 5-V supplies. The integrated CAN transceivers comply with ISO 11898-2 and ISO 11898-5.

Texas Instruments (USA) also manufactures SBCs with CAN transceivers. For example, the TPS99119 component implements an SPI interface, watchdogs, LDO regulators, and a LIN transceiver. The functional architecture features under-voltage and over-voltage monitoring, current limits, temperature warning flags, and over-temperature shutdown on all regulator outputs.

Other SBC suppliers are Elmos (Germany), On Semiconductors (USA), and AMS (Austria). The AS8650 by AMS combines power management and a CAN transceiver. The integrated DC-DC converter features three LDO voltage regulators. The SBC provides a CAN transceiver for bit-rates up to 1 Mbit/s with low-power mode (ISO 11898-5). Additionally, it is equipped with a configurable watchdog.

SBCs were originally intended for automotive applications. However, they are also interesting for mobile machines and battery-powered systems. The chips range from simple implementations, a collection of hard-wired functions so-to-speak, to configurable state-machine controlled solutions.

In the near future, such SBCs will also support CAN bit-rates higher than 1 Mbit/s in order to be used in CAN FD networks. The first wave of such products will be qualified for 2 Mbit/s. They are also recommended for CAN FD networks using a 1-Mbit/s dataphase bit-rate. They feature higher symmetry, which gives the system designer more options for the network topology. SBCs supporting 5 Mbit/s CAN transmissions will follow.

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Texas Instruments