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Author: Admin | 2025-04-28
Sarvang Sanghavi, Ravish Shah, Upendra Somashekaraiah (eInfochips) Abstract:The continuous need for reduced size of the chip in the VLSI industry brings exciting challenges to the layout engineers for designing better and high-performing integrated circuits, which needs to consume low power even while reducing the silicon area and cost involved. Internal power is a component of the total power consumed by the chip, which is becoming more challenging to handle with the shrinking technology nodes. There are many methods, which have been used to reduce the internal power in the industry. In this article, we will discuss the usage of multibit flops in the design to reduce the power component of the ICs. We will also discuss other design challenges faced while using the multibit flip-flops (MBFF) and ways to overcome them. Introduction to multibit flop: Multibit flops are used to reduce the power in ASIC without affecting the performance of the design. Multibit flops as the name suggests have multiple D and Q pins. Generally, two bit and four bit versions are available in the library. A two bit multibit flops will have D0, D1, Q0, Q1 pins along with a common clock, scan_in and scan_enable pins. In a two bit flop, the scan_in pin of the second bit flop is connected to the first flop Q pin (Q0), so that they are in scanning order. The layout of the multibit flop is designed in a compact manner so that the effective area of the multibit flop is much lesser than the added area of the single bit flops (Fig2, Fig3, and Fig4). For example, two bit multibit flop has roughly 20% lesser area than the combined area of the two single bit flops of the same drive strength. A two bit flip-flop can be designed to have a single cell row height or two cell row height (single cell row two bit flop is shown in Fig3), while a four bit flop is designed with two rows height (Fig4). Fig1: Simplified representation of two bit flip-flop Fig2: A single bit flop layout view Fig3: Two bit flop layout view
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