A low power cmos decision feedback equalizer for a serial link receiver

Abstract

As the channel length of the transistors scale down, the capabilities of digital computing of each chip are increased. Hence, the amount of data which should communicate from chip to chip is increased.There are two methods to communicate with large amount of data between chips. One is increasing anumber of I/O drivers. However, the physical dimensions of chip restrict many I/O drivers. The other method is increasing the data rate per each pin. However, the bandwidth of the electrical channel is limited, so the channel loss can be problem with high data rate. To solve this problem, much effort has been made toward compensating severe channel loss in high speed chip-to-chip communications such as ASIC to ASIC systems. The effect of the channel loss is inter-symbol interference (ISI) which causes wrong sampled data, but this ISI problem can be handled at the receivers by using equalizers with active components. In the receivers, there are three types of equalizers which are widely used to remove ISI. One is continuous-time linear equalizer (CTLE) which is easy to implement but increases high frequency noise. Another is feed forward equalizer (FFE) which does not have feedback delay, but it also amplifies high frequency noise. The other is decision feedback equalizer (DFE) which does not increase noise. In respect of removing ISI as increasing the signal-to-noise ratio (SNR), DFE can be beneficial, but the power consumption of DFE is higher than other equalizer types. Thus, we should consider the trade-off between power consumptionand SNR to compensate the ISI.A novel equalizers has been proposed to enhance the figure-of-merit (FOM) of the equalizers. Inprevious DFEs, many-tap DFEs or DFEs with other type equalizers are used to restore the data from the severe channel loss. However, these many-tap DFE cause increased power consumption and area. This paper proposes a low power 1-tap DFE using unfixed tap coecient as compensating high attenuation. By adopting...