Eduardo Aldrete-Vidrio

Electrothermal Design Procedure to Observe RF Circuit Power and Linearity Characteristics With a Homodyne Differential Temperature Sensor

The focus in this paper is on the extraction of RF circuit performance characteristics from the dc output of an on-chip temperature sensor. Any RF input signal can be applied to excite the circuit under examination because only dissipated power levels are measured, which makes this approach attractive for online thermal monitoring and built-in test scenarios. A fully differential sensor topology is introduced that has been specifically designed for the proposed method by constructing it with a wide dynamic range, programmable sensitivity to dc, and RF power dissipation, as well as compatibility with CMOS technology. This paper also presents an outline of a procedure to model the local electrothermal coupling between heat sources and the sensor, which is used to define the temperature sensors specifications as well as to predict the thermal signature of the circuit under test. A prototype chip with an RF amplifier and temperature sensor was fabricated in a conventional 0.18-μm CMOS technology. The proposed concepts were validated by correlating RF measurements at 1 GHz with the measured dc voltage output of the on-chip sensor and the simulation results, demonstrating that the RF power dissipation can be monitored and the 1-dB compression point can be estimated with less than 1-dB error. The sensor circuitry occupies a die area of 0.012 mm2, which can be shared when several on-chip locations are observed by placement of multiple temperature-sensing parasitic bipolar devices.

Strategies for built-in characterization testing and performance monitoring of analog RF circuits with temperature measurements

This paper presents two approaches to characterize RF circuits with built-in differential temperature measurements, namely the homodyne and heterodyne methods. Both non-invasive methods are analyzed theoretically and discussed with regard to the respective trade-offs associated with practical off-chip methodologies as well as on-chip measurement scenarios. Strategies are defined to extract the center frequency and 1 dB compression point of a narrow-band LNA operating around 1 GHz. The proposed techniques are experimentally demonstrated using a compact and efficient on-chip temperature sensor for built-in test purposes that has a power consumption of 15 μW and a layout area of 0.005 mm 2 in a 0.25 μm CMOS technology. Validating results from off-chip interferometer-based temperature measurements and conventional electrical characterization results are compared with the on-chip measurements, showing the capability of the techniques to estimate the center frequency and 1 dB compression point of the LNA with errors of approximately 6% and 0.5 dB, respectively.

Differential Temperature Sensors Fully Compatible With a 0.35-

Four differential temperature sensors, two passive and two active, designed and fabricated in a 0.35-m standard CMOS technology, are presented and characterized. Passive sensors are based on integrated thermopiles. Each one consists of eight thermocouples (16 strips) serially connected: poly1-poly2 for the first thermopile and poly1-P+diffusion for the second one. The active sensors are based on differential amplifiers, one with single-ended output and the other with differential output. Lateral parasitic bipolar transistors are used as temperature transducer devices. Both simulated and experimental characterizations are presented. The high sensitivity of active differential temperature sensors proves the feasibility of such sensors to observe the power dissipated by devices and circuits embedded in the same silicon die, with applications to the test and characterization of circuits, packaging characterization and compensation of thermal gradients, among others.

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The observation of spectral components of the power dissipated by devices and circuits in integrated circuits (IC) by temperature measurements is limited by the bandwidth of either the temperature transducer or the intrinsic cut-off frequency provided by the thermal coupling inside the chip. In this paper, we use a heterodyne method to observe the high-frequency behavior of circuits and devices by means of low-frequency lock-in temperature measurements. As experimental results, two applications of the technique are presented: detection of hot spots in ICs activated by high-frequency electrical signals and the observation of the frequency response of an integrated resistor through temperature measurements. The heterodyne method has been used in this paper with four different measurement techniques: embedded differential BiCMOS temperature sensor, laser reflectometer, laser interferometer and internal IR laser deflection meter.

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Built-in test and on-chip calibration features are becoming essential for reliable wireless connectivity of next generation devices suffering from increasing process variations in CMOS technologies. This paper contains an overview of contemporary self-test and performance enhancement strategies for single-chip transceivers. In general, a trend has emerged to combine several techniques involving process variability monitoring, digital calibration, and tuning of analog circuits. Special attention is directed towards the investigation of temperature as an observable for process variations, given that thermal coupling through the silicon substrate has recently been demonstrated as mechanism to monitor the performances of analog circuits. Both Monte Carlo simulations and experimental results are presented in this paper to show that circuit-level specifications exhibit correlations with silicon surface temperature changes. Since temperature changes can be measured with efficient on-chip differential temperature sensors, a conceptual outline is given for the use of temperature sensors as alternative process variation monitors.

A heterodyne method for the thermal observation of the electrical behavior of high-frequency integrated circuits

In this work a new technique for the observation and characterization of high-frequency electrical characteristics of analog and radio frequency integrated circuits (RFIC) by on-chip frequency-domain thermal measurements is proposed. The analysis presented confirms that low-frequency spectral components of the temperature sensed close to analog circuits contain information about some high-frequency characteristics of the circuits observed. The feasibility of this RF testing technique is confirmed experimentally. It is non-invasive and can be implemented with a very small area overhead. The technique is applied, as an example, to obtain some electrical characteristic of an RF low noise amplifier (LNA)

Survey of Robustness Enhancement Techniques for Wireless Systems-on-a-Chip and Study of Temperature as Observable for Process Variations

In this presentation we cover how to use low frequency or DC temperature measurements to observe figures of merit of high frequency analogue circuits.