Brake-by-wire is rapidly becoming a core chassis technology in software-defined vehicles. However, while much of the automotive industry's design focus is on centralizing computer platforms, the physical action of stopping a vehicle takes place at the wheel. This location places stringent demands on the electronics of the corner modules, which must provide operational power in the event of a failure and accurate wheel speed data in confined, vibration-prone, and thermally stressful spaces, all while meeting the highest standards of functional safety.
Today, designers are forced to combine generic safety PMICs, independent wheel speed decoders, and discrete power component assemblies. Besides increasing costs and taking up valuable board space, this approach multiplies potential points of failure precisely where reliability is most critical.
A single device, designed for the task
With an on-chip Wheel Speed Sensor Interface (WSSI), the A81415 safety PMIC decodes standard 2-level AK protocols, 2-level pulse-width modulation (PWM), and 3-level (standard and high-resolution) PWM without the need for complex analog circuitry or a separate decoder IC. Incorporating a fully integrated buck-boost pre-regulator, five low-dropout regulators (LDOs), and a single-inductor architecture that requires no external switches or diodes, the A81415 eliminates up to nine external components and enables savings of up to $4 per vehicle in semiconductor bill of materials (BOM), providing significant production-scale cost advantages for original equipment manufacturers (OEMs).
This unprecedented level of integration frees up more than 50% of the usable board space, providing the brake caliper with critical design headroom. Because the physical layer of wheel speed data is handled internally by the PMIC and the decoded data is shared via a serial peripheral interface (SPI), the A81415 reduces latency in the safety-critical loop and frees up MCU bandwidth for faster braking response. Low-noise power rails are specifically tuned to feed Allegro's TMR XtremeSense™ angle sensors, ensuring that the entire switching and clamping force signal chain is optimized as a single, coherent, high-resolution system, from wheel to caliper.
The 12V to 48V fast track for corner modules
True brake-by-wire operation requires components capable of withstanding the harshest electrical environments. Based on Allegro’s proprietary automotive-grade 0 process and combined with the APM81815 pre-regulator and 48V gate drivers, the A81415 forms a complete chipset that remains operational even in the event of a failure. This modular approach offers Tier 1 suppliers a fast track to migrate proven 12V braking architectures directly to next-generation 48V corner modules without redesign or bulky external transient protection systems. “Intelligent chassis systems demand that the sensing and power electronics at the wheel operate as a single unit,” said Peter Wells, director of the high-performance power business line at Allegro MicroSystems. "Allegro has combined our leadership in wheel speed sensing and our expertise in highly reliable power management in our new PMIC to offer our customers a simpler, safer and highly scalable foundation for modern vehicle brake-by-wire systems.".
Features and benefits of the A81415:
Integrated wheel speed detection: The on-chip WSSI decodes 2-level, PWM, AK and high-definition protocols, eliminating the need for a separate decoder IC.
Cost and space savings: Eliminates up to nine external components, saving up to $4.00 in semiconductor bill of materials (BOM) per vehicle and more than 50% of printed circuit board (PCB) area.
ASIL-D and AEC-Q100 Certification: The two monitoring circuits and integrated fault management meet the highest safety standards without the need for external protection circuits.
Scalable from 12V to 48V: Works natively in 12V systems with a simple upgrade path to 48V corner modules when combined with the APM81815.
