Steps to Minimize IR Drop in Integrated Circuit Design

What is IR Drop?

IR drop, also known as voltage drop, refers to the reduction in voltage that occurs when an electric current flows through a conductor or a circuit. It is caused by the resistance of the conductor, which converts some of the electrical energy into heat. IR drop can affect the performance and efficiency of electronic devices and circuits, as it may lead to a decrease in the voltage level available for components to function properly. Mitigating IR drop is crucial in ensuring optimal power delivery and preventing potential issues such as signal distortion or device malfunction.

Best Practices to Minimize IR Drop

Power Delivery Network (PDN) Design

The PDN distributes power to various sections of the chip, necessitating a well-designed system. An effective PDN should minimize resistance and inductance to mitigate voltage drop. Additionally, it should incorporate an adequate number of voltage regulators to ensure each chip section receives the necessary voltage.

EMIR analysis, performed by signoff power integrity tools like Ansys RedHawk-SC, generates Build Quality Metrics (BQM) to assess how effectively a PDN layout meets circuit power demands pre-placement. This enables rapid identification and rectification of weak power supply areas early in the design process.

Layout Optimization

Increasing metal wire width and minimizing vias in the power grid reduce resistance and inductance, thereby decreasing IR drop. Adhering to high-speed design guidelines and optimizing layouts further aids in reducing voltage drop within PDNs.

Ansys PowerArtist optimizes power delivery networks by estimating power at the Register-Transfer Level (RTL).

Strategic Placement of Power and Ground Planes

Proper positioning of power and ground planes is critical for minimizing IR drop in sensitive analog, radio frequency (RF), and mixed-signal designs. Locating these planes close to transistors diminishes resistance and inductance in the power distribution network, consequently minimizing IR drop.

Mitigating Local Current Demand

Placement algorithms can address the density of local current drawn by neighboring cells, ensuring adequate spacing to improve Dynamic Voltage Drop (DVD) without compromising timing results significantly.

On-Chip Decoupling Capacitors

Incorporating on-chip decoupling capacitors creates a low-impedance pathway for high-frequency noise, reducing voltage drop. Placed near the power and ground pins of transistors, these capacitors provide a local energy source, lessening the demand for substantial current from the PDN.

IR Drop Analysis Tools

Utilizing IR drop analysis tools aids in predicting and measuring voltage drop across different chip segments. These tools offer visual representations of voltage drop distribution, facilitating identification of root causes and areas requiring enhancement.

Types of IR drops