Robust DC-DC Converter using a-InGaZnO TFTs for Self-Contained Electronics

This paper demonstrates, for the first time, the effect of bias stress on the performance of two amorphous Indiumgallium-Zinc Oxide (a-IGZO) thin-film transistor (TFTs) based DC-DC converters, when they are tested close to real-world operating conditions. The individual circuits (Dickson and Cross-coupled DC-DC converters) are characterized under normal ambient with and without continuous bias stress. Under no stress condition, Dickson and Cross-coupled converters are showing almost constant voltages of 3.8V (8.5V), 3.9V (9.3V), when tested at different clock frequencies of 0.25, 1, 5 MHz with a single (a series of two) thin-film batteries, where each battery shows 3V output voltage. When a Cross-coupled DC-DC converter with 6V input is driving other similar circuit, the final output of 16.5V is noticed, demonstrating self-contained electronics with oxide TFTs. Further, individual circuits were stressed for 18000 seconds to mimic real-world conditions. The Dickson (Cross-coupled) converter has shown a variation of 12% (0.7%) and 5% (0.5%) in output DC voltage when tested with a single and a series connection of two batteries, respectively. This work opens a window for self-contained electronics with oxide TFTs under real-world operating conditions.