| An integrated, mixed-signal sensor interface system, called the Low Speed Channel, was developed for extreme environment applications. The sensor interface uses Silicon-Germanium (SiGe) technology and special design techniques to ensure operation in high-radiation environments, with a temperature range of -180°C to +125°C, without the protection of "warm boxes." The system has a configurable Wheatstone bridge to allow for use with quarter, half, or full bridge resistive sensors. The differential bridge voltage is sampled by a flying capacitor circuit and incorporates a programmable gain amplifier. Shift registers are used to program the gain and configuration of the bridge. Digital-to-analog converters are used to provide offset voltage adjustment and a sensor bias current. The Low Speed Channel was fabricated and tested across the required wide temperature range. Circuit design issues were addressed to ensure performance of the channel. The final design was verified through simulations across temperature, supply voltage variation, and process skew. Finally, an application of the Low Speed Channel is presented in a multiple-sensor, dual-chip system developed for NASA. |
