Dissertation Defense

Scalable Energy-Recovery Architectures

Tai-Chuan Ou

Energy efficiency is a critical challenge for today's integrated circuits,

especially for high-end digital signal processing and communications that require both

high throughput and low energy dissipation for extended battery life. Charge-recovery

logic recovers and reuses charge using inductive elements and has the potential to

achieve order-of-magnitude improvement in energy efficiency while maintaining high

performance. However, the lack of large-scale high-speed silicon demonstrations and

inductor area overheads are two major concerns.

This dissertation focuses on scalable charge-recovery designs. We present a

semi-automated design flow to enable the design of large-scale charge-recovery

chips. We also present a new architecture that uses in-package inductors, eliminating

the area overheads caused by the use of integrated inductors in high-performance

charge-recovery chips.

To demonstrate our semi-automated flow, which uses custom-designed standard-
cell-like dynamic cells, we have designed a 576-bit charge-recovery low-density parity-
check (LDPC) decoder chip. Functioning correctly at clock speeds above 1GHz, this

prototype is the first-ever demonstration of a GHz-speed charge-recovery chip of

significant complexity. In terms of energy consumption, this chip improves over recent

state-of-the-art LDPCs by at least 1.3— with comparable or better area efficiency.

To demonstrate our architecture for eliminating inductor overheads, we have

designed a charge-recovery LDPC decoder chip with in-package inductors. This test-
chip has been fabricated in a 65nm CMOS flip-chip process. A custom 6-layer FC-BGA

package substrate has been designed with 16 inductors embedded in the fifth layer of

the package substrate, yielding higher Q and significantly improving area efficiency and

energy efficiency compared to their on-chip counterparts. From measurements, this

chip achieves at least 2.3— lower energy consumption with even better area efficiency

over state-of-the-art published designs.

Sponsored by


Faculty Host

Marios Papaefthymiou