Low-Power High-Speed Current Mode Logic Using Tunnel-FETs

Current mode logic (CML) circuits have been widely used in high-speed data transceivers. The lower-voltage-swing makes the switching speed of CML much higher than the static logic can achieve, so it is worthy to adopt the CML circuits at the cost of higher power consumption in the high-speed applications. In order to obtain a better power efficiency (Frequency /power) in CML, it is critical to reduce the power consumption while maintaining the high operating frequency. This paper proposes an alternative approach by building the CML circuits with tunneling-field-effect-transistor (Tunnel FETs or TFETs) to achieve a high-throughput, low-voltage interface circuit design. By taking advantage of its steep subthreshold slope (less than 60 mV Idec), TFET exhibits the same on/off current ratio at the input voltage swing interval much lower than that of the MOSFETs, which enables the supply voltage scaling in CML circuits. For a design target data-rate (20 Gbps for multiplexer and 50 Gbps for buffer), our simulations show that the proposed TFET CML circuits are able to reduce the supply voltage from 0.6 V in conventional Si FinFET CML circuits to as low as 0.3 V while using the same constant tail current. As a result, a power consumption reduction of approximately 50% is achieved by the proposed TFET CML circuits, making the TFET CML approach a promising candidate for future low-power, high-performance applications.