Driver Impedance Calibration for High Speed Interfaces Without Precision Resistor
Siddharth Katare · 2025
Impedance matching between driver and channel is critical for ensuring signal integrity of high-speed interfaces. This paper presents a method to calibrate the driver impedance without relying on the precision external resistors. The proposed method uses a process and temperature monitor placed on-die to recover relevant information to calibrate the impedance. This information is used to calibrate the pull-down path of the driver. The pull-up path is calibrated using the pull-down path as reference. The circuit was designed in 22nm CMOS process node. The error in driver impedance was reduced from ±30% to ±13% by process calibration. The error was further reduced by enabling temperature tracking.