Prashant Narang

Bio: Prashant Narang is an academic researcher from Cadence Design Systems. The author has contributed to research in topics: Low-power electronics & Logic gate. The author has an hindex of 1, co-authored 1 publications receiving 26 citations.

Capture power reduction using clock gating aware test generation

Abstract: Scan-based manufacturing test of low power designs often exceeds the very tight functional constraints on average and instantaneous logic switching. The logic activity during the shift and launch-capture of test pattern data may lead to excessive power consumption and voltage droop. This paper focuses on the management of instantaneous power during the capture phase. By taking advantage of the existing clock gating circuitry and selectively holding the value of some scan flip-flops, switching activity during the capture cycles of a test can be reduced. The effectiveness of this technique is demonstrated on several industrial designs that show up to 30% (55%) reduction in instantaneous (average) capture switching.

A clock-gating based capture power droop reduction methodology for at-speed scan testing

Abstract: Excessive power dissipation caused by large amount of switching activities has been a major issue in scan-based testing. For large designs, the excessive switching activities during launch cycle can cause severe power droop, which cannot be recovered before capture cycle, rendering the at-speed scan testing more susceptible to the power droop. In this paper, we present a methodology to avoid power droop during scan capture without compromising at-speed test coverage. It is based on the use of a low area overhead hardware controller to control the clock gates. The methodology is ATPG (Automatic Test Pattern Generation)-independent, hence pattern generation time is not affected and pattern manipulation is not required. The effectiveness of this technique is demonstrated on several industrial designs.

Design for Testability Support for Launch and Capture Power Reduction in Launch-Off-Shift and Launch-Off-Capture Testing

Abstract: At-speed or even faster-than-at-speed testing of VLSI circuits aims for high-quality screening of the circuits by targeting performance-related faults. On one hand, a compact test set with highly effective patterns, each detecting multiple delay faults, is desirable for lower test costs. On the other hand, such patterns increase switching activity during launch and capture operations. Patterns optimized for quality and cost may thus end up violating peak-power constraints, resulting in yield loss, while pattern generation under low switching activity constraints may lead to loss in test quality and/or pattern count inflation. In this paper, we propose design for testability (DfT) support for enabling the use of a set of patterns optimized for cost and quality as is, yet in a low power manner; we develop three different DfT mechanisms, one for launch-off shift, one for launch-off capture, and one for mixed at-speed testing. The proposed DfT support enables a design partitioning approach, where any given set of patterns, generated in a power-unaware manner, can be utilized to test the design regions one at a time, reducing both launch and capture power in a design-flow-compatible manner. This way, the test pattern count and quality of the optimized test set can be preserved, while lowering the launch/capture power.

Formal Test Point Insertion for Region-based Low-Capture-Power Compact At-Speed Scan Test

Abstract: Launch-Switching-Activity (LSA) is a serious problem during at-speed testing of integrated circuits, since localized LSA may lead to severe IR-drop and thus failures. The excessive LSA is conventionally mitigated by reducing the switching activity through special low-power test generation techniques, typically resulting in severe test pattern inflation and high test costs. This work introduces a novel concept of Low-Capture-Power Test Points (LCP-TPs), which are inserted to reduce switching activity in critical High-Capture-Power (HCP) regions. LCP-TPs also help in retaining high test compaction capability. An optimization- SAT based procedure is proposed to compute a small set of optimal LCP-TP locations for compact at-speed test sets with effective capture power reduction. Experimental results clearly demonstrate the advantages of LCP-TP insertion.

State of the art low capture power methodology

Abstract: Power consumption during test can be significantly higher than during normal functional mode. This paper presents a low power Automated Test Pattern Generation (ATPG) flow for managing capture power in today's power critical designs. It introduces a novel method for sequentially enabling the on-chip clock controllers to generate accurate low power ATPG patterns respecting the power specifications of the design. The effectiveness of the method is demonstrated on several industrial designs that show up power issues during test mode.

Power droop reduction via clock-gating for at-speed scan testing

Abstract: A clock gating mechanism controls power within an integrated circuit device. One or more clock gating circuits are configured to couple a system clock to a different portion of the integrated circuit device. A logic circuit applies an enabling signal to one of the clock gating circuits to control whether the system clock passes through the clock gating circuit to a portion of the integrated circuit device associated with the clock gating circuit. A plurality of scan flip-flops is configured to provide a binary code to the logic circuit, where the binary code indicates to the logic circuit that the enabling signal should be applied to the clock gating circuit. One advantage of the disclosed technique is that power droop during at-speed testing of a device is reduced without significantly increasing the quantity of test vectors or reducing test coverage, resulting in greater test yields and lower test times.