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This paper presents a digital readout integrated circuit (DROIC) for small pitch medium-wave infrared (MWIR) starring focal plane arrays (FPAs). To overcome the limited in-pixel resolution of such DROICs, the concept of error shaping is introduced in pulse frequency modulation (PFM)-based pixels. Multiple integration operations are performed in a single frame and the residue charge from each integration phase is retained and injected into the next charge packet. This over-integration routine provides a high pass noise transfer function (NTF) equivalent to what is obtained in a first order sigma delta modulator. The concise structure of a PFM analog-to-digital converter (ADC) lends itself well to such an operation inside the pixel, while consuming low power. Along with a theoretical analysis of the technique, a prototype based on a $16\times 16$ array and sinc decimation filters is developed to demonstrate the performance of the proposed DROIC. With an in-pixel resolution of 5 bits and over-integration ratio (OIR) of 128, 395 noise electrons are demonstrated at full-well fill from the test array fabricated in a 90 nm bulk-CMOS process. [ABSTRACT FROM AUTHOR]

The growth of IoT applications requires DC-DC converters to have small printed circuit board (PCB) areas and high efficiency over a wide load range. A multi-mode operation of DC-DC converters, therefore, is often necessary to achieve this high efficiency over a wide load range. This paper introduces a tri-mode DC-DC buck converter for IoT applications. The tri-mode operation with PWM, PFM, and multiple-sawtooth PWM (MSPWM) modes helps to retain the high efficiency over the wide load range. The MSPWM mode also enhances a noise margin of the converter, ensuring a regular switching operation at an ultra-light load condition. With a load current prediction scheme, the proposed tri-mode converter requires neither additional load current sensor nor multiple mode controllers. In addition, a soft-start operation is employed to prevent an in-rush current. The proposed tri-mode buck converter has been fabricated through a 0.18- $\mu \text{m}$ CMOS process with a chip area of 0.97 mm $\times0.88$ mm. A load-dependent seamless mode transition is realized, and a maximum converter efficiency of 91% has been measured with a 7.4-MHz switching frequency. [ABSTRACT FROM AUTHOR]

It is essential to retain improved efficiency in a dc–dc converter over a wide load current range to extend the battery-life in portable devices. This requires a multi-mode controller, consisting of pulse-width-modulation (PWM) and pulse-frequency-modulation (PFM) schemes. However, existing approaches attempt to integrate structurally different controllers; thus it is difficult to achieve a seamless controller transition. While a digital platform offers controller configurations, it remains difficult to identify a suitable digital PWM/PFM technique and decide on its sampling mechanism to achieve stable behavior. This paper proposes a unified digital PWM/PFM scheme which shares a common digital PWM (DPWM) block and has the provisions for online controller configuration and automatic (switching) frequency adaptation. The proposed scheme retains improved efficiency over a wide operating range and inherently achieves seamless controller transitions. Further, a unified discrete-time framework is proposed for the analysis and design of the proposed multi-mode controller. Buck and boost converter prototypes are tested and the proposed controller is implemented using a field-programmable-gate-array device. [ABSTRACT FROM AUTHOR]

This paper introduces and analyzes an ultra-low power and low-complexity analog IR-UWB radio system for unlicensed audio streaming which achieves continuous wave FM performance but exploiting aggressively duty-cycled signaling. At the TX, signal is modulated using a VCO which generates pulses with variable rate (PRF modulation), for an average of \sim600 kHz. At the RX an asynchronous and interference-robust detector regenerates the modulated signal at half frequency without requiring phase-locking, which is successively processed by a passive FM detector. The obtained demodulated signal is filtered using a fourth order Sallen-Key cell. The TX and RX modules based on commercial components draw 1.89 and 10 mA from 100 mAh Lithium-ion rechargeable batteries (1 \times TX and 2 \times RX) and include an integrated TX/RX chipset in a 130 nm RFCMOS technology which operates at 3.5 GHz center frequency and 1.2 V supply. The radio system transmits audio with THD <1%, provides an SNR of 64 dB (aligned with FM radio and compact cassettes) and has a frequency response 110 Hz–17 kHz, for a continuous play time of 50 h (TX) and 12 h (RX), and 2.5 m radio range. [ABSTRACT FROM PUBLISHER]

In this paper, we propose to study voltage controlled oscillators (VCOs) based on the equivalence with pulse frequency modulators (PFMs). This approach is applied to the analysis of VCO-based analog-to-digital converters (VCO-ADCs) and deviates significantly from the conventional interpretation, where VCO-ADCs have been described as the first-order $\Delta \Sigma $ modulators. A first advantage of our approach is that it unveils systematic error components not described by the equivalence with a conventional $\Delta \Sigma $ modulator. A second advantage is that, by a proper selection of the pulses generated by the PFM, we can theoretically construct an open loop VCO-ADC with an arbitrary noise shaping order. Unfortunately, with the exception of the first-order noise shaping case, the required pulse waveforms cannot easily be implemented on the circuit level. However, we describe circuit techniques to achieve a good approximation of the required pulse waveforms, which can easily be implemented by practical circuits. Finally, our approach enables a straightforward description of multistage $\Delta \Sigma $ modulator architectures, which is an alternative and practically feasible way to realize a VCO-ADC with extended noise shaping. [ABSTRACT FROM PUBLISHER]

A flexible bandwidth, blind sub-Nyquist sampling approach referred to as the quadrature analog-to-information converter (QAIC) is proposed. The QAIC relaxes the analog frontend bandwidth requirements at the cost of some added complexity compared to the modulated wideband converter (MWC) for an overall improvement in sensitivity and energy consumption. An approach for detailed frequency domain analysis of the proposed system with linear impairments is developed. A process for selecting QAIC parameter values is illustrated through examples. The benefits of the QAIC are highlighted with cognitive radio use cases where a wide range of spectrum is observed at various resolution bandwidth settings. We demonstrate that the energy consumption of the QAIC is potentially two orders of magnitude lower than the swept-tuned spectrum analyzer (STSA) and an order of magnitude lower than the MWC. We also demonstrate that the QAIC significantly improves upon the sensitivity performance delivered by the MWC. [ABSTRACT FROM AUTHOR]

We present a novel randomized wrapped-around pulse position modulation (RWAPPM) scheme for digital modulators of dc–dc converters. Unlike the reported modulation schemes that require a varying switching period (thereby resulting in high attenuation or complete elimination of discrete harmonics), the proposed RWAPPM conversely requires only a constant switching period (thereby advantageous in terms of easy realization in hardware), and yet, its discrete harmonics are negligible. We derive an expression for the spectrum of the RWAPPM scheme to analytically obtain the peak spectral power and ripple noise voltage of RWAPPM. This expression further provides insight to the parameters that influence the RWAPPM spectrum. We benchmark the RWAPPM scheme against the ubiquitous conventional pulsewidth modulation scheme and six reported (randomized and frequency modulation) schemes. The RWAPPM scheme features negligible discrete harmonics [\leq -158 dB relative to full scale (dBFS)], and among the modulation schemes, it features the lowest peak spectral power at -26.6 dBFS (before low-pass filtering) and relatively low ripple noise at 2 mVrms (after low-pass filtering) for a 3.6–2.5-V conversion and an effective switching frequency of 120 kHz. We verify the derived expression and attributes of the RWAPPM spectrum by computer simulations and on the basis of experimental measurements on a dc–dc converter. [ABSTRACT FROM PUBLISHER]