Design, Implementation, and Experimental Verification of 5 Gbps, 800 Mrad TID and SEU-Tolerant Optical Modulators Drivers

This paper presents the design and experimental verification of two drivers designed to be compliant with the high radiation dose levels present in the inner layers of the CERN's Large Hadron Collider (LHC) experimental chambers. The drivers, designed to face up to 800 Mrad (SiO2) Total Ionizing Dose, are able to sustain up to 5 Gbps bit-rate links when integrated in a 65 nm CMOS technology. They are designed to drive two Silicon Photonics optical modulators, Mach Zehnder Modulator and Ring Resonator, which have shown high rad-tolerant levels. The high dose level hardness of the drivers has been achieved by adopting the following Radiation Hardening By Design (RHBD) techniques: enhancement of the MOSFETs model to take into account the effects of high radiation dose levels and of single event effects on the devices, avoidance of using P-MOSFETs, increase of the minimum MOSFET lengths for the switching devices, and the use of Enclosed Layout Transistors shape plus some layout precautions. Moreover, to increase the drivers speed, techniques like buffer chain and inductive peaking are used in the drivers' design. The experimental results have verified the matching of the high-speed high-voltage constraint required by the application. The Total Ionization Dose tests have shown, at 800 Mrad (SiO2), a 30% and 25% amplitude reduction of the output signals eye diagrams of the Mach Zehnder Modulator driver and of the Ring Resonator driver, respectively. In the worst case, in which the drivers will be placed within 5 cm from the beamline of the CMS experiment of the upgraded LHC, the heavy ions tests have shown a BER of 5.19e-8.