A Low-Power Two-Tap Voltage-Mode Transmitter With Precisely Matched Output Impedance Using an Embedded Calibration Circuit

Abstract

In this brief, a low-power two-tap voltage-mode transmitter (TX) with precisely matched output impedance using an embedded calibration circuit for dc-coupled unidirectional links is proposed. The proposed TX adopts an N-over-N driver with a supply voltage of 0.4 V in order to reduce the power consumption of the output driver. Its output driver is configured as a two-tap Finite Impulse Response (FIR) filter in order to compensate for channel loss at high frequency. In addition, the proposed embedded impedance calibration circuit precisely matches the impedance of the output driver to the channel characteristic impedance by using the receiver termination resistor instead of external reference resistors. The proposed two-tap voltage-mode TX is fabricated using a 90-nm low-power CMOS process technology and occupies an active area of 0.054 mm(2). The measurement results show that the matching error of the output impedance is between -0.6% and +0.8%, and the power efficiency is 0.75 pJ/b without equalization and 0.94 pJ/b with 6-dB equalization, at a data rate of 5.0 Gb/s.