TID in a Switched-Capacitor FPAA: Degradation and Partial Inactivity Windows Due to Compensating Effects in MOS Transistors

Abstract

Results of irradiation experiments on a 0.6 m switched-capacitor analog array indicate a sudden recovery of the FPAA performance degradation during the irradiation phase. The main parameter considered to check the performance of the device is the total harmonic distortion of the processed analog signals. The observed recovery is associated with the compensating effects of oxide and interface trapped charge in the NMOS transistors of the array in a particular window of the accumulated dose received by the device. Experimental results are discussed and simulations performed to confirm the hypotheses for the observed phenomenon.Index Terms-Field programmable analog arrays (FPAAs), inactivity windows, radiation effects, total ionizing dose (TID).

Reliability Analysis of 0.5μm CMOS Operational Amplifiers under TID Effects

“…Results are shown in Fig 20, in which the inactivity windows for the PMOS-DA architecture can be noticed. A similar behavior was observed in our practical radiation experiments [13].…”

“…It was observed a sudden recovery of the THD during a specific window of the irradiation phase. This fail-recovery pattern may be associated to partial inactivity windows in the analog switches of the device as well as in the device OpAmps, as described in [13] and firstly observed in [14] on irradiated commercial analog switches.…”

“…In a recent work of our research group, the effects of TID in a switched-capacitor (SC) programmable analog device were investigated [13]. In that work the THD (Total Harmonic Distortion) of the signal processed by a second order analog SC filter, programmed into the device, was monitored during the device irradiation with a Cobalt-60 gamma ray source.…”

“…The effects of charge buildup due to TID were simulated by injecting threshold shifts in the transistors model, directly in the model cards of the considered technology (AMI 0.5mm). The injected deviations were carried out according to the typical behavior of the threshold voltage shifts (according to [14]) for the dose rate applied in the practical experiment previously performed by the authors (1krad/h), whose results have motivated this investigation [13]. This behavior is depicted in Fig.…”

“…In a previous work of our group the effects of TID in a 0.6mm switched-capacitor (SC) programma-ble analog device were investigated [13]. In that work it was observed a sudden recovery of the device performance during a specific interval of the irradiation phase (after significant signal degradation was established).…”