The development and expansion and of semi-autonomous and autonomous driving is quickly approaching with the advancement of infotainment and advanced driver assistance systems (ADAS). With HD video, control satellite and over-the-air radio, GPS and mobile device connection and back-up cameras, systems once reserved for only high-end cars are becoming more commonplace.
Yet, this performance is not free. With the increase in performance and processing requirements comes an increase in power requirements for the system-on-chip (SoC) , both in number of rails and current requirements, whether the system is based on TI’s “Jacinto 6” or TDAx SoC families. One way to manage these increased power requirements is to use an integrated power management IC (PMIC).
In these systems, a low-voltage PMIC is supplied by a pre-regulated 3.3V or 5V input. It has all the power rails to power the low-voltage supply rails needed in the system: processor core, graphics core, DDR memory, I/O devices, as well as the analog supplies such as phase lock loops (PLLs) and physical layer devices. Using one IC in place of many to power all of these rails makes both schematic design and layout simpler.
To further simplify the system solution, a low-voltage PMIC like the TPS659039-Q1 integrates more than just power regulation functions. Because the SoCs have many power supplies, they typically have power-up and power-down sequencing requirements that must be met in order to guarantee reliability of the SoC. Instead of using an external microcontroller to sequence the rails, this low-voltage PMIC has hardware-controlled sequencing programmed in to the device in its one-time-programmable (OTP) memory. The OTP not only contains power sequence information but also the boot voltages and other default states. Since different SoCs have different supply voltages and sequence requirements, the same low-voltage PMIC can be used with different OTP programming in order to support a variety of SoCs used in infotainment and ADAS systems.
In addition, automotive environments have strict requirements on electromagnetic interference (EMI), the most common of which is the CISPR25 standard. In order to reduce the EMI from many switch-mode power supplies SMPS integrated in one device, all SMPS are synchronized together so they all use the same switching clock. The default switching frequency is 2.2MHz, which keeps the emissions outside of the AM band, while keeping inductor size small to save board space. This switching clock can be either an input to the PMIC or outputted from the PMIC in order to synchronize all SMPS across different ICs on the same system. This will reduce EMI emissions not only from the PMIC itself, but the whole system.
Do you have questions about other ways PMICs can help your system design?
For more information about these platforms, and technical discussion of power supplies in automotive, please see the following pages: