Research Area
The research laboratory focus on mixed signal system design, using state-of-the-art CMOS process.
Moore's prediction that the number of transistors doubles about every two years, has not reached its limit yet (5 nm process demonstrated as of 2020). The shrinking technology has brought many performance advantages in the integrated circuit (IC) by improving power, transistor density and bandwidth, but reduced supply voltage, ro and leakage issue cast uncertainty on the traditional mixed signal circuit design methodologies. From a different angle, the challenging design environments require new circuit and system approaches based on brilliant design ideas to overcome the uncertainty and it is an opportunity for circuit engineers like us.
The market share of non-memory semiconductor is 66% of the entire semiconductor industry currently according to WSTS. The lab.'s researches involve in non-memory system IC designs and require understanding in system-level loop behaviors and circuit-level transistor operation principles. We seek the system-level design approaches in perspective of analog/mixed domain. More specifically, we deal with technological design performance issues, such as phase noise / circuit non-linearity / inter-symbol interference in wireline/wireless communication systems.
Mixed signal IC research area is largely about investigating methodologies to design IC that performs the targeting functions operating with analog signal, digital signal or both (mixed). The circuits defined in digital domain assume digital signals that move rail-to-rail at every nodes in which the power consumption follows the metric P = C x freq x V^2 and normally low power performances can be expected. However, in some cases when the circuit functions involve inevitably analog signal nature (i.e. analog front-end in communication systems), analog domain design approaches are more efficient in terms of power, area and noise performances. We use both design domains when we design circuits but more focus is on analog-side approaches.
Whether analog or digital block, all integrated circuits are normally fabricated in one single silicon die. Depending on the type of signal the circuit deals with, however, a circuit can largely be categorized into analog or digital one.
An analog circuit processes analog signals such as wireless signal received from antenna or voice signal from mike. The most common aim of analog circuits is amplification where physical size voltage movement from input to output increases while maintaining its overall shape. It means that the circuits have a good linearity so that it should not distort shape of the signal during amplification (sensitive to noise). To build an analog circuit block, integrated passive components - R,L,C are used along with active components - NMOS/PMOS (CMOS). Trade-offs between design parameters (component size) and circuit performances are too complex to be automated and normally the layout works are conducted by hand - full-customed design. In a digital circuit the processed signals have rail-to-rail digital format with a constant time period. Since the information of signal is put in voltage levels - 0 or 1 only at a constant timing, the signal is strong to noise. The digital blocks use CMOS only out of all types of integrated devices and generally benefit from automated RTL design.
Both analog and digital circuits are crucial to build an IC system. IC industry desperately demand engineers who can carry analog design and automated digital design. However, normally, it is very hard to find someone who can do both comfortably.
Two more specific IC design areas are the major research interest of the lab. We use both analog/digital circuits to build our IC systems.