In the field of embedded hardware design, the DDR power circuit, as a core power supply unit, directly impacts chip performance and long-term device stability. As a high-performance processor, the RK3588 places stringent requirements on the layout, routing, and component selection of the VCC_DDR power circuit. This article, based on official design specifications, breaks down the key technical aspects of DDR power circuit design from five core dimensions: copper pouring, vias, decoupling capacitors, trace topology, and trace width standards, providing standardized design references for hardware engineers.

I. VCC_DDR Copper Lamination: Focusing on "Current Requirements" to Ensure Uninterrupted Power Supply Paths

Copper lamination is the "main power supply artery" of the DDR power circuit. Its design directly determines current transmission efficiency and voltage drop control. Two key points require attention:

• Prioritizing Effective Line Width Calculation

The copper lamination connecting to the RK3588 power pins must meet the chip's maximum current requirements. The effective line width must be calculated in advance using the current-line width conversion formula (such as the IPC-2221 standard) to avoid localized overheating or voltage loss due to insufficient line width.

• Avoiding Excessive Via Segmentation

Vias on the copper lamination path segment the current path. The number and distribution of vias must be controlled to ensure that every copper lamination path connecting to the CPU power pin is "complete and uninterrupted," without obvious breaks.

II. Layer Change Vias and GND Vias: "Quantity Matching" is Key to Decoupling Capacitor Effectiveness

When the VCC_DDR power supply needs to be rerouted, the via design must follow the principle of "voltage reduction and decoupling protection," specifically:

• Power Vias: "Dense Layout" of 9 or More

When changing layers, at least 9 power vias with a specification of 0.5*0.3mm must be placed. Increasing the number of vias reduces parasitic inductance and resistance, minimizes voltage drop caused by layer change, and ensures power integrity.

• GND Vias: "Quantity Equal" to Power Vias

The number of grounding vias for decoupling capacitors must match the number of corresponding power vias. Insufficient GND vias will lead to increased capacitor loop impedance, significantly weakening the decoupling capacitor's ability to suppress power supply noise and affecting DDR signal stability.

III. Decoupling Capacitor Layout: "Proximity Principle + Precise Alignment" Maximizes Noise Suppression

Decoupling capacitors act as "noise filters" for DDR power supplies. Their placement directly determines filtering efficiency and must strictly adhere to the following specifications (see diagram for clearer understanding):

• Core Pin Capacitors: Precise Backside Alignment

As shown in "Figure : Schematic Diagram of RK3588 Chip VCC_DDR Power Pin Decoupling Capacitors," the decoupling capacitors near the RK3588's VCC_DDR power pin in the schematic must be placed on the back of the PCB corresponding to that power pin. This achieves the shortest path connection between the pin and the capacitor, quickly absorbing high-frequency noise near the pin.

• GND PAD capacitors: "Close to" the chip's center GND pin

The GND PAD of the decoupling capacitors should be placed as close as possible to the center GND pin of the RK3588 chip to shorten the grounding path, reduce grounding impedance, and prevent noise from coupling to other signals through the grounding loop.

• Other capacitors: "Close to chip" layout

The remaining decoupling capacitors for non-core pins should be placed as close as possible to the RK3588 chip, following the layout logic in "Figure : Placement of decoupling capacitors on the back of power supply pins," ensuring that all capacitors effectively suppress noise on the power bus.

IV. Power Pin Routing: "One Hole, One Pin + Tile Topology" Optimizes Current Distribution

The VCC_DDR power pin routing of the RK3588 requires a "precise matching + topology optimization" design. Specific standards are as follows:

• Pin and Via: One-to-one correspondence:

Each VCC_DDR power pin must correspond to an independent via to avoid uneven current distribution and localized power shortages caused by multiple pins sharing vias.

• Top Layer Routing:

Tile Cross-Connection: As shown in "Figure VCC_DDR & VDDQ_DDR Power Pin 'Tile' Chain", the top layer routing must use a 'tile' topology. Cross-connection achieves uniform current distribution. It is recommended that the trace width be controlled at 10mil to balance current carrying capacity and routing space requirements.

• LPDDR4x Mode: Dedicated Connection Solution

When using RK3588 with LPDDR4x memory, the layout shown in "Figure: RK3588 Chip LPDDR4x Mode VCC_DDR/VCC0V6_DDR Power Pin Routing and Vias" must be followed to adapt to the power supply characteristics of LPDDR4x and ensure the stability of high-frequency memory operation.

V. Trace Width and Copper Coverage: Zonal Management, Balancing Current and Space

The trace width and copper coverage of the VCC_DDR power supply must be designed according to "CPU Area" and "Peripheral Area," while coordinating with other signal routing. Specific requirements are as follows:

• Hard Trace Width Standards

1. CPU Area (around power pins): Trace width must not be less than 120mil to meet the current requirements of centralized power supply to the chip pins;
2. Peripheral Area (path from power input to CPU): Trace width must not be less than 200mil to reduce voltage loss over long distances.

• Preferred Copper Coverage Design

Use large-area copper coverage instead of thin traces whenever possible. Increasing the copper area further reduces impedance and voltage drop, improving power supply stability.

• Other Signal Avoidance

Non-DDR power supply signal vias should be placed "regularly and avoid haphazard placement." This is to allow sufficient space for power copper pours and to minimize the damage to ground copper pours caused by vias, ensuring the integrity of the ground plane (refer to Figure).

Summary: The "Core Logic" of DDR Power Circuit Design

The essence of RK3588 DDR power circuit design is to provide a stable and clean power supply environment for DDR memory through "precise current control, minimized path impedance, and efficient noise suppression." These five key points are interconnected. From copper pours and vias to capacitor placement and trace topology, each step must strictly adhere to specifications to avoid issues such as device crashes, memory errors, and performance fluctuations due to negligence in details.

For hardware engineers, in actual design, it is necessary to combine the specifications with engineering practice, taking into account the actual scenario such as the number of PCB layers and layout space, while also utilizing simulation tools (such as Altium Designer). The power integrity analysis function verifies the design effectiveness and ensures the reliability and stability of the final product.