Design Engineer | Signal Integrity | Power Integrity | Honeywell | Analog Circuit Design | Transmission Lines | PCIe | Ethernet | High-Speed Digital Design
Power Distribution Network (PDN): The Backbone of Power Integrity Every high-speed system depends on a robust Power Distribution Network (PDN) to ensure that ICs receive a stable supply voltage. A weak PDN leads to voltage drop, noise, and unpredictable failures no matter how strong the rest of the design is. ⸻ Why PDN Matters ? When an IC switches, it draws sudden bursts of current specially in SoCs/FPGA/ASICs where Transistors switches rapidly. Any impedance in the PDN causes a voltage drop: ΔV = I transient X Z(PDN) If the PDN impedance is too high, the voltage ripple exceeds the IC’s tolerance, leading to timing errors and system instability. ⸻ ZPDN and Target Impedance To design a robust PDN, we calculate a Target Impedance (Z target), which the PDN must stay below across frequency. Z(target) = ΔV/I transient 🔹 Example: • IC voltage = 1.8 V • Allowed ripple = 5% = 0.09 V • Max transient current = 2 A Z(target) = 0.09/2 = 45 mΩ This means the PDN impedance must remain below 45 mΩ across the frequency band of interest. ⸻ Key Takeaway ZPDN is the central metric of Power Integrity just as eye diagrams define Signal Integrity, Impedance defines PDN stability. By designing to meet Ztarget, we ensure clean power delivery, robust margins, and system reliability.
Design Engineer | Signal Integrity | Power Integrity | Honeywell | Analog Circuit Design | Transmission Lines | PCIe | Ethernet | High-Speed Digital Design
4wKeeping the PDN impedance below the target value across frequency is always challenging. For those starting out in Power Integrity, how do you usually check if your design is meeting the Z(target) — by simulation, measurement, or simple calculations?