Chan-Hong Chern

8.4 A 28Gb/s 1pJ/b shared-inductor optical receiver with 56% chip-area reduction in 28nm CMOS

Next-generation high-performance computing systems require high-bandwidth serial links to transport high-speed data streams among computational blocks. Optical links have recently attracted attention due to their low channel loss at high frequencies, requiring simpler equalization circuits than electrical links. The energy-efficiency of optical links can thus be significantly improved [1-5]. Broadband techniques such as inductive peaking are commonly used in highspeed optical transceivers for bandwidth enhancement at the expense of the chip area. Inductor-less receivers have been proposed [4,6] to reduce chip area but they usually consume more power or have lower data rates at given technology nodes. In this paper, we present two optical receivers that each consists of a pseudodifferential CMOS push-pull transimpedance amplifier (TIA), a DC offset-cancellation circuit, a limiting amplifier (LA) with interleaving active-feedback [6], and a T-Coil fT-doubler output buffer. The block diagram and experimental setup are shown in Fig. 8.4.1. The capacitance of the off-chip GaAs PIN photodetector (PD), which is wire-bonded to the CMOS receiver, is 100fF with 0.4A/W responsivity. The two optical receivers have identical designs except for the LA, in which two different inductive peaking techniques, conventional and shared-inductor, are designed and fabricated on the same die in 28nm CMOS technology.

A 2.7GHz 3.9mW Mesh-BJT LC-VCO with −204dBc/Hz FOM in 65nm CMOS

Standards with narrow channel spacing have stringent requirements for in-band phase noise of oscillator, which is dominated by up-converted flicker noise. In this paper, we propose a LC-tank voltage-controlled oscillator (VCO) that utilizes novel Mesh-BJT structure to suppress in-band phase-noise while maintaining low power consumption. The proposed 2.7GHz LC-VCO consumes 3.9mW from a 1.5V supply and the figures of merit (FOM) at 10KHz and 100KHz offsets are -222dBc/Hz and -204dBc/Hz in 65nm CMOS. The Mesh-BJT is compatible with standard CMOS and no extra masks are required. To our best knowledge, this is the best FOM ever reported at low offsets (<;100KHz) for VCO in standard CMOS.