A system basis chip, or SBC, is an integrated circuit (IC) that combines many typical building blocks of a system including transceivers, linear regulators and switching regulators. While these integrated devices can offer size and cost savings in a number of applications, they don’t work in every case.
For applications where an SBC isn’t a good fit, it might be beneficial to build a disc rete implementation of these aforementioned building blocks, and that is what I mean by the term “discrete SBC.” In this post, I’ll describe some scenarios where building discrete SBCs can solve system requirements, and what additional benefits you’ll gain by using discrete solutions.
Versatile power topologies
Different nodes in an automobile will have widely varying performance requirements during different input transients. For example, gateway modules, which route critical information around a vehicle, will sometimes need to continue normal operation through cold-crank input transients as low as 4.0V. Given this requirement, you’ll need some form of boost converter to keep the output voltage rails in regulation through the low-input voltage transient.
An example solution would be to create a two-stage regulator with a wide-input-voltage boost regulator to an intermediate voltage, followed by a wide-input-voltage buck regulator to the desired output voltage. Figure 1 shows a block diagram of this power scheme.
Figure 1: Boost regulator followed by buck regulator topology
While this solution requires two regulators, the additional benefits are:
In my second example, a discrete SBC solution may be beneficial in nodes that need to operate through start-stop transients where battery input voltages can dip down as low or lower than 5.5V. If the module requires both a regulated 5V supply for a CAN transceiver and a 3.3V regulated supply for the microcontroller, a wide-input-voltage buck converter set to 3.3V followed by a small low-input-voltage boost converter can be a competitive solution. Figure 2 shows this topology.
Figure 2: Buck regulator followed by boost regulator topology
The additional benefit here is that since the battery’s input voltage immediately bucks down to a regulated low voltage, it only requires one wide-input-voltage regulator. Therefore, the 3.3V to 5.0V boost regulator can be a low-input-voltage, low-current device, saving cost.
Scalable product families and controller products
Discrete families often come with drop in-compatible family members with different current ratings. This makes it easier for you to scale your power supplies for low-, mid- and high-end applications without having to redesign the board.
Some examples of TI families that do this include:
Devices within each of these families are pin-to-pin equivalent and interchangeable with one another depending on your design’s load current or feature requirements. And because both buck and boost regulators have controller products that use external field-effect transistors (FETs) and diodes, you can easily scale these products depending on the load-current requirements of each design variant.
While not all applications have the same requirements as the two examples I’ve described here, being willing to look at discrete solutions offers superior flexibility and scalability.
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