Automotive Electronics: Designing a Reliable Power Tree

Modern automotive SoCs demand stable, precise power. One voltage dip or transient spike can cause failures, making automotive electronics and power tree design critical under real vehicle conditions.

This article gives direct, solution-focused guidance based on the Monolithic Power Systems (MPS) power tree design methodology. It includes practical numbers and common pitfalls engineers face.

Why Automotive SoCs Need a Power Tree

Automotive batteries (12 V systems) can see transient over-voltage and under-voltage events during normal operation. Consumer DC/DC converters built for PC-like 12 V buses are not well-suited for these conditions.

SoCs in ADAS and infotainment platforms can require more than 10 distinct power rails. These range from hundreds of amperes to a few milliamps per rail.

A power tree handles these multiple rails by converting battery power into regulated buses. The tree ensures each rail gets stable voltage with minimal noise.

SoC Power Requirements: Practical Example

Rail	Voltage	Current	Transient Load	Slew Rate	Tolerance
VDD_CORE	0.85 V	60	40	40 A/µs	±3%
1V8_GPIO	1.8 V	5	2.5	2.5 A/µs	±5%
3V3_GPIO	3.3 V	5	2.5	2.5 A/µs	±5%
1V8_analog	1.8 V	1.5	0.75	0.75 A/µs	±5%
DDR_VDD	1.05 V	6	3	3 A/µs	±3%
DDR_VDDQ	0.6 V	6	3	3 A/µs	±5%

High transient load handling and voltage precision are critical.

Step-By-Step Power Tree Design

Step 1

Select Pre-Regulator Topology

Choose between buck, buck-boost, or combined topologies. Use buck for warm-crank events and buck-boost for severe cold-crank operations. Splitting pre-regulators for heavy loads reduces stress per branch.

Step 2

Set Bus Voltage

Select a 5 V bus to reduce output current and simplify converter selection. Most low-current DC/DC converters tolerate up to 5.5 V input. Calculate pre-regulator power rating using rail requirements and efficiency (~89%).

• Pre-Regulator 1 output: ~57 W → 11.5 A at 5 V

•Pre-Regulator 2 output: ~45 W → 9.1 A at 5 V

Step 3

Select Appropriate ICs

Use automotive-grade ICs with wide input voltage and high transient tolerance. Include pre-regulators, PoL converters, and ideal diode controllers. Evaluate efficiency, footprint, and heat dissipation.

Step 4

Integrate Protection

Avoid standard diodes for reverse current; they waste power. Use ideal diode controllers instead. Ensure regulators handle load dumps and voltage spikes. Add thermal and overcurrent protection to prevent cascading failures.

Common Automotive Electronics Design Mistakes and Pitfalls

Ignoring transient requirements. Design converters for worst-case loads, not nominal current.
Incorrect bus voltage selection. Evaluate trade-offs between bus voltage, current, and efficiency.
Using standard diodes for reverse protection. Use ideal diode controllers to minimize power loss.
Under-specing automotive conditions. Always use AEC-Q100 qualified automotive ICs.

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Engineer-Ready Guidelines

Choose pre-regulator topology based on automotive transient conditions.
Select bus voltage that minimizes converter complexity.
Size for transient loads, not just nominal currents.
Use automotive-grade ICs and efficient protection.

Designing a power tree becomes predictable when you use real numbers and avoid common pitfalls engineers face.

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Why Partner with Acton for your Power Tree Design

Acton Technology supports automotive electronics and power tree design across Southeast Asia. We supply automotive-grade passive, active, discrete, electromechanical, mechanical, and sensor components for ADAS, infotainment, and vehicle control systems.

We work with engineers and procurement teams to support AEC-Q compliant power tree designs and reliable component supply from design to production.

For product inquiries or sourcing support, contact contact@acton-tech.com.