Chandradevi Ulaganathan

SiGe BiCMOS Precision Voltage References for Extreme Temperature Range Electronics

We present the first investigation of the optimal implementation of SiGe BiCMOS precision voltage references for extreme temperature range applications (+120 degC to -180 degC and below). We have developed and fabricated two unique Ge profiles optimized specifically for cryogenic operation, and for the first time compare the impact of Ge profile shape on precision voltage reference performance down to -180 degC. Our best case reference achieves a 28.1 ppm/ degC temperature coefficient over +27 degC to -180 degC, more than adequate for the intended lunar electronics applications

A High-Slew Rate SiGe BiCMOS Operational Amplifier for Operation Down to Deep Cryogenic Temperatures

We investigate, for the first time, the design and implementation of a high-slew rate op-amp in SiGe BiCMOS technology capable of operation across very wide temperature ranges, and down to deep cryogenic temperatures. We achieve the first monolithic op-amp (for any material system) capable of operating reliably down to 4.3 K. Two variants of the SiGe BiCMOS op-amp were implemented using alternative biasing schemes, and the effects of temperature on these biasing schemes, and their impact on the overall op-amp performance, is investigated

A new approach to designing electronic systems for operation in extreme environments: Part I - The SiGe Remote Sensor Interface

We have described the modeling, circuit design, system integration, and measurement of a Remote Sensor Interface (Figure 20) that took place over a span of 5 years and 8 fabrication cycles. It was conceived as part of the Multi-Chip Module (MCM) shown in Figure 21, which also includes a digital control chip for clocking, programming, and read-out. Further work beyond the scope of this was performed to validate the RSI for the extreme environmental conditions of a lunar mission, and individual blocks are presently.

SiGe BiCMOS 12-bit 8-channel low power Wilkinson ADC

A multichannel low power analog-to-digital converter (ADC) designed, fabricated and tested in 0.5-mum Silicon Germanium BiCMOS process is reported. The 12-bit ADC features 8 input channels, each having a 10-Ksps sampling rate and an input voltage range of 1.2 V. The ADC architecture, comprised of a ramp generator, comparators, and a Gray code counter, is discussed along with design details of the primary blocks. Measurement data shows a differential nonlinearity of less than 0.5 LSB and an approximate accuracy of 10 bits.

A SiGe BiCMOS instrumentation channel for extreme environment applications

A instrumentation channel has been designed, implemented and tested in a 0.5-mum SiGe BiCMOS process. The circuit features a reconfigurable Wheatstone bridge network that interfaces a range of external sensors to signal processing circuits. Also, analog sampling has been implemented in the channel using a flying capacitor configuration. Measurement results show the instrumentation channel supports input signals up to 200 Hz.

Radiation response of SiGe BiCMOS mixed-signal circuits intended for emerging lunar applications

The effects of proton irradiation on the performance of key devices and mixed-signal circuits fabricated in a SiGe BiCMOS IC design platform and intended for emerging lunar missions are presented. High-voltage (HV) transistors, SiGe bandgap reference (BGR) circuits, a general-purpose high input impedance operational amplifier (op amp), and a 12-bit digital-to-analog converter (DAC) are investigated. The circuits were designed and implemented in a first-generation SiGe BiCMOS technology and were irradiated with 63 MeV protons. The degradation due to proton fluence in each device and circuit was found to be minor, suggesting that SiGe HBT BiCMOS technology could be a robust platform for building electronic components intended for operation under extreme environments.

An ultra-low voltage self-startup charge pump for energy harvesting applications

An ultra-low voltage, self-starting, switched-capacitor based charge pump is proposed for energy harvesting applications. The integrated linear charge pump topology presented in this work has been optimized for low-voltage start-up. The control signals for the charge-transfer switches (CTS), generated using two clock phases, reduce reverse currents and thus improve the efficiency of the converter. Adiabatic switching techniques have been employed to reduce the switching losses associated with the CTS gate control. This design has been implemented in a 130-nm CMOS process. Simulation results demonstrate a low startup voltage of 125 mV with efficiency of 62 % for a static current load of 0.1 μA.

PVT Compensation for Wilkinson Single-Slope Measurement Systems

A pulse-width locked loop (PWLL) circuit is reported that compensates for process, voltage, and temperature (PVT) variations of a linear ramp generator within a 12-bit multi-channel Wilkinson (single-slope integrating) Analog-to-Digital converter (ADC). This PWLL was designed and fabricated in a 0.5- μm Silicon Germanium (SiGe) BiCMOS process. Simulation and silicon measurement data are shown that demonstrate a large improvement in the accuracy of the PVT-compensated ADC over the uncompensated ADC.

A sige BiCMOS instrumentation channel for extreme environment applications

A instrumentation channel has been designed, implemented and tested in a 0.5-mum SiGe BiCMOS process. The circuit features a reconfigurable Wheatstone bridge network that interfaces a range of external sensors to signal processing circuits. Also, analog sampling has been implemented in the channel using a flying capacitor configuration. Measurement results show the instrumentation channel supports input signals up to 200 Hz.