Radiation-hard voltage reference: from measurements-based VerilogA model of standard diodes and DTMOS to circuit realization

Reference voltage required by electronic measurement and monitoring systems must be stable with variable environmental conditions, like temperature. In ionizing environments the stability must be ensured also under exposure to radiation. A systematic approach to radiation tolerant bandgap reference design is presented. Initially reference devices: standard diodes and custom designed DTMOS (dynamic threshold MOS) are characterized at different temperatures. The extracted parameters show that temperature dependence largely varies with device type and DTMOS gate and drain bias conditions. Consequently each device requires different parametric balance to achieve a stable voltage reference. A VerilogA model applicable for circuit simulations, including this temperature dependence, is adapted for both standard diodes and DTMOS. Finally the XREFIC testchip with a family of voltage references is introduced. It includes circuits based on standard diode as well as DTMOS-based, with much better radiation tolerance.