The SBC is an integrated circuit that includes several independent functional blocks, in a single way, with the main purpose of saving space.
The functional blocks contained meet specific needs for automotive industry, which is why they are used on most electronic control units in the field (ECU).
Functional blocks of an SBC
The structure of the functional blocks contained may differ from one product to another, depending on its requirements. Next, we will take as an example the IC manufactured by STMicroelectronics - L99PM62GXP. Thus, an SBC can perform the following functions:
- Watch Dogs;
- CAN / LIN transceiver;
- Voltage stabilizer;
- Wake-up;
- Outputs;
- Operational amplifiers;
- Communication between uC and SBC is done through a Serial Peripheral Interface (SPI) protocol.
Block diagram of the SBC L99PM62GXP
Watchdog function
Watchdog is a function that has the role of making sure that the CPU works accordingly. Otherwise, the SBC's watchdog function will reset the CPU.
In other words, a watchdog timer is a electronic timer or software which is used to detect and recover circuit faults.
Transceiver LIN, CAN
The SBC may contain controllers and transceivers for serial communications with other ECUs.
LIN (Local Interconnect Network) is a serial network protocol used for communication between vehicle components. It is a single-serial network protocol that accepts communications up to 19,2 Kbit / s at a bus length of 40 meters.
CAN Master (English Controller Area Network) is a serial bus used in the automotive industry, in order to ensure communication between several microcontrollers without the use of a host computer. Originally developed by Bosch in 1983, the specification was officially launched in 1986 (CAN 1.2) and standardized under the name ISO 11898. Subsequently, several semiconductor manufacturers (Intel, Philips, Infineon, Texas Instruments, Motorola) have implemented CAN-based peripherals. In September 1991, Bosch released the 2nd version of the specification (CAN 2.0).
The voltage stabilizer (s) of an SBC
Within the SBC circuit, there may be one or more 5V voltage stabilizer blocks. In the case presented in the article (L99PM62GXP), we have two 5V voltage stabilizers (V1, V2).
Wake-up function
This function allows the SBC to wake the uC from sleep mode if there are active inputs.
SBC outputs
An SBC can contain multiple outputs, both HS (High Side) and LS (Low Side). The outputs of the SBC circuit are relatively small current outputs (maximum 400mA).
SBC operational amplifiers
SBC operational amplifiers are specially designed for linear amplification of an input between 0V and 3V, thus being ideal for voltage amplification on a shunt connected to GND.
The advantages of an SBC
Containing several functional blocks in the same IC, the SBC offers several advantages in addition to saving space.
- All the functional blocks contained have the same references without the need for individual filters;
- Self diagnostics of all the blocks and the possibility of their monitoring by uC through a single BUS line;
- Configuring the operation of all blocks by setting registers. These registers are written via the SPI line.
Bibliography:
https://www.st.com/
https://en.wikipedia.org/wiki/Watchdog_timer
https://en.wikipedia.org/wiki/Local_Interconnect_Network
https://ro.wikipedia.org/wiki/Controller_Area_Network
https://eepower.com/
SPI is the interface, the protocol is above the physical layer. But yes SBC is a good IC to have, but it can be a pain in the ass 🙂
Using an SBC is the cheapest method of controlling the inputs and outputs of an ECU. It's also responsible for giving you accurate diagnostic data. Of course, all reported is through SPI.