SSZTD61 November 2024 LM5137F-Q1 , TPS62883-Q1
The rapid evolution of advanced driver assistance systems (ADAS) increases the complexity and demand for real-time data processing, which requires high-performance processors to handle tasks such as object recognition, sensor fusion and decision-making. This increased complexity introduces new challenges on the power-management side. Starting with the vehicle’s battery (12V, 24V or 48V), a preregulator steps down the battery voltage to feed point-of-load (PoL) buck converters, supplying the processor with the precise voltages needed for optimal operation. Additionally, there is strong focus on meeting functional safety requirements for the entire system, with the power stage playing a critical role to enable meeting these requirements.
Solutions such as the 80V LM5137F-Q1 dual-channel buck controller and the 6V, 30A TPS62883-Q1 dual-phase buck converter provide power to high-current automotive processors while helping systems achieve functional safety compliance up to Automotive Safety Integrity Level (ASIL) D.
Enabling up to ASIL D systems requirements
The TPS62883-Q1 is a TI Functional Safety-Compliant 30A buck converter developed according to International Organization for Standardization (ISO) 26262. The device is part of a scalable product family offering pin-compatible options with current ratings from 12A to 30A, and supports a stackable architecture to deliver loads beyond 100A, enabling the power requirements for modern ADAS systems-on-a-chip (SoCs) where the demand for higher currents is ever-increasing. Figure 1 shows two TPS62883-Q1 converters in a stacked configuration.
Figure 1 Two TPS62883-Q1 devices in a
stacked configurationThe TPS62833-Q1 helps remove external output voltage supervision through safety-compliant internal monitoring. Also, a change in the output voltage through I2C takes effect at the same time, for both the output voltage control loop as well as the internal output voltage monitoring. This feature eliminates blind spots in the output voltage monitoring during dynamic or adaptive voltage scaling. The communication through the I2C-compatible interface can be cyclic redundancy check (CRC) protected so that the MCU can detect and flag bit errors in bus communication.
Also, the TPS62883-Q1 provides warnings based on its thermal-warning threshold and enters a safe state in case of critical fault conditions in the system such as undervoltage or overvoltage lockout. The device also features a nINT fault pin that signals to the microcontroller (MCU) when a fault condition occurs, which can then take the necessary action depending on the application requirements.
Improving load transient response for ADAS processor applications
Meeting high current requirements is not the only challenge in power supplies. In fact, load transient response is essential for maintaining reliable operation of high-performance processors. Rapid changes in processing demand cause sudden changes in power consumption, leading to voltage undershoots and overshoots, potentially triggering malfunctions. A fast load-transient response is crucial for reliable operation of these SoCs.
SoCs specify a defined tolerance for each of their supply voltages. The core voltage rail is the most important one because the dynamics in supply currents are high, the voltage is low, and tolerance is in the order of millivolts.
The total budget for the load transient depends on several factors, as illustrated in Figure 2. In general, you want a large remaining window for the load-transient voltage deviation, as this allows lower output capacitance. The TPS62883-Q1 provides ±0.5% DC output voltage accuracy as well as internal voltage monitoring, which removes the additional tolerance introduced by external voltage supervision.
Figure 2 Load transient budget based on
core-supply voltage tolerancesThe TPS62883-Q1 also incorporates flexible droop compensation, allowing you to tailor the droop behavior closely to the requirements of your design. This feature scales the nominal output voltage based on the output current, such that the output voltage scales linearly between zero and full output current.
As shown in Figure 3, the output voltage is set slightly higher than its nominal value at a no-load condition and slightly lower than its nominal value at a maximum load condition. Droop compensation therefore helps keep the output voltage within a certain tolerance band in case of a heavy load step or at a load release.
Additionally, the dual-phase design of the TPS62883-Q1 provides higher loop bandwidth and significantly lower output voltage ripple compared to single-phase designs, offering extra headroom for load transients. The combination of these features enables you to reduce the amount of output capacitance and meet stringent load-transient requirements, while cutting costs and reducing overall system complexity.
Figure 3 Voltage scaling with output
currentTo help streamline your functional safety system-level certification, TI provides industry-standard reports and additional resources – including IC-level documentation such as functional safety FIT rate and failure-mode effects and diagnostic analysis (FMEDA).
Conclusion
The complexity of ADAS continues to increase significantly as vehicles progress toward autonomous driving, resulting in greater power demands for application processors. Concurrently, functional safety is paramount, as these systems need to be reliable for users to depend on. The TPS62883-Q1, when used in a stackable configuration, achieves core power beyond 100A and in parallel helps enable system designs to achieve functional safety compliance as high as ASIL D.
Additional resources
- Download the TPS62883-Q1 data sheet.
- Check out the "TPS6288x-Q1 buck converter evaluation module" user's guide.
- Read the technical article, “Achieving functional safety compliance in automotive off-battery buck preregulator designs."
- Learn more about stackability in the "Operating TPS6287X-Q1 Devices in a Stacked Configuration" application note.
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