Decoding Qualcomm Automotive Domain Controller first-stage Power Supply Design: Performance Test Measurement Analysis

The rapid development of the new energy vehicle industry has driven explosive growth across various industrial chains. Vehicle intelligence and autonomous driving have become the most critical competitive edge directions for new energy vehicles, bringing new challenges and opportunities for highly integrated central brains and domain controllers, especially in terms of the reliability, high power density, switch power supply, EMC, high efficiency, and low cost of DC-DC power supplies.

Qualcomm, as a supplier of smart cockpit domain controllers, holds a significant position with SA8155 and SA8295. The conflicts between transient current, stable operating current, standby power efficiency, cost, and EMC design in the central domain controller SOC first-stage power supply (from battery input to first-stage conversion power supply) pose a major challenge for BUCK power supply design. How to address and balance these conflicts is the technical direction for joint efforts by switch power supply architecture, power chip, inductor, MOSFET, and capacitor manufacturers.

1- Content Overview

This article focuses on the first-stage power supply design for automotive central domain controllers with large dynamic switching power supply current (100-300%), exploring the design of DC-DC switching power supplies, including power supply solutions, inductor and capacitor selection, and other design methods, while addressing challenges in volume, cost, efficiency, and performance, and discussing practical implementation design.

This chapter takes Qualcomm SA8295 domain controllers as an example to explore and implement first-stage BUCK switching power supply test and validation, demonstrating whether the test results meet the expected design.

This series of articles consists of three chapters:

01- Decoding Qualcomm Automotive Domain Controller First-Stage Power Supply Design: Power Supply Design and Calculation

02- Decoding Qualcomm Automotive Domain Controller First-Stage Power Supply Design: Schematic Design and PCB Design

03- Decoding Qualcomm Automotive Domain Controller First-Stage Power Supply Design: Performance Test Measurement Analysis (This Chapter)

2- Verification Objectives

SA8295 Transient Current Requirements are as follows:

Note: NPU activation requires additional current consumption. This design does not include the NPU design current (3A+3A).

3- Test Environment and Conditions

3.1Test Conditions

Ambient temperature: 25°C (actual 24-27°C, calculated as 25°C)

3.2 Test Instruments and Test Methods

3.3 Schematics and PCB

Schematic Diagram

PCB

4- Test Validation

Verify the performance of ripple, voltage accuracy, stability, temperature rise, and efficiency exhibited by the steady-state load capability at different voltages (9-16V). Limited by space, select key performance indicators for test validation.

①Ripple: Ripple under different input voltages and load currents;

②Voltage Accuracy: Output voltage accuracy under different input voltages and load currents;

③Load Current Capability: Output current voltage, efficiency curve testing;

④Temperature Rise Characteristics: Verify whether the operating conditions meet the requirements.

4.1 Low-voltage load capacity (9.0V)

4.2 Normal Voltage Load Capability (13.5V)

4.3 High-voltage load capacity (16.0V)

4.4 Continuous Current Test

5.Test Summary

5.1 Test Results

Several noteworthy points:

①The core design goal is to meet transient current and stable operating current requirements. If designed entirely according to the maximum values, costs and volume would increase (reduced PCB design density), but in reality, there is no such condition where it operates stably at 18A;

②Ripple is easily met using ceramic capacitors, all below 50mV;

③The power inductor has excellent DCR and current soft saturation characteristics, actual output 21A current;

④This design can operate above 20 amperes for short periods, maintaining good levels of 8-12A efficiency and temperature rise.

6- Key Materials Bom

7- Inductor Selection

As an important component of the first-stage power supply in automotive domain controllers, the performance of inductors is crucial to the reliability and conversion efficiency of DC-DC switching power supplies. In this design solution, the CODACA automotive-grade Molded Power Inductor VSEB0660-1R0M is adopted. This series of inductors features low loss, high efficiency, wide application frequency range, strong saturation current resistance, low heat generation, and high cost-performance ratio. The slim design boasts an industry-leading power density, making it highly suitable for the development and application of Qualcomm platforms.