Toward Temperature Tracking With Unipolar Metal-Oxide Thin-Film SAR C-2C ADC on Plastic

Abstract

The maturity of metal-oxide thin-film transistors (TFT) highlights opportunities to develop robust and low-cost electronics on flexible and stretchable substrates over large area in an industry-compatible technology. Internet-of-Everything applications with sensor nodes are driving the development of analog-to-digital converters (ADCs). In this paper, a self-biased and self-digital-controlled successive approximation ADC with integrated references and sensor read-in circuitry together with a printed negative temperature coefficient (NTC) sensor using unipolar dual-gate metal-oxide (InGaZnO) TFTs is demonstrated. The system is operated at a clock of up to 400 Hz and a total power dissipation of 245 mW (73 µW from analog) at a maximum power supply of 30 V is measured. The radio-frequency identification-ready ADC comprises of a total of 1394 indium-gallium-zinc oxide TFTs and 31 metal-insulatormetal capacitors. A figure of merit of 26 nJ/c.s. is achieved from the ADC driven from external microcontroller. The robustness of the various blocks of the chip is characterized and the yield is discussed.

Flexible 16nJ/c.s. 134S/s 6b MIM C-2C ADC using Dual Gate Self-aligned Unipolar Metal-Oxide TFTs

“…Table I displays a thin-film ADC state-of-the-art comparison and performance summary table. The presented TFT C-2C ADC on flexible substrate has 40% smaller FoM compared to state-of-the-art for unipolar technologies [2], [3], [10], [12] and is only 2nJ/cs larger than state-of-the-art of complementary TFT technologies. Moreover, the proposed ADC achieves DNL/INL figures smaller than 0.9LSB, demonstrating no missing codes.…”

“…A microcontroller is used to control the ADC. Recently, TFT digital control circuits have been demonstrated successfully [2] with more than 1300 IGZO TFTs for a 5b ADC on flexible substrate.…”

“…More specifically, multiple ADC topology implementations using LAE technologies (a-Si, organic or low-temperature polycrystalline silicon) on glass or flexible substrates have been presented in the literature [8]- [12]. Recently, more specifically Δ-Σ [3] or successive approximation (SAR) implementations [2] are enabling new temperature sensing applications counting on uniformity over large areas, stability and relative high mobility of IGZO TFTs. Other applications, such as in-panel fingerprint sensing on mobile displays, require faster sampling rates than temperature sensing.…”

AMOLED Displays with In-Pixel Photodetector

“…The ADC is converting the analog voltage received from the CSA to a digital code. Various TFT-based analog blocks have been demonstrated in the literature [18][19][20][21][22][23][24]. Metal-oxide TFT technologies are preferable due to uniformity over large areas, very low leakage currents, and lower cost over area.…”

In-Panel 31.17dB 140kHz 87µW Unipolar Dual-Gate In-Ga-Zn-O Charge-Sense Amplifier for 500dpi Sensor Array on Flexible Displays

“…Research towards thin-film transistor (TFT) technologies based on In-Ga-Zn-O have gained an increased maturity and attractive performance characteristics enabling analog signal processing and increasingly more complex systems on flexible substrates [1]- [4]. Analog signal conversion based on In-Ga-Zn-O TFTs can be implemented in fingerprint sensor arrays for direct integration on mobile AMOLED displays.…”