High-Temperature, Bulk-CMOS Integrated Circuits for a Distributed Control System-Performance Results

Abstract

Four integrated circuits (ICs) have been developed to provide sensing, actuation, and power conversion capabilities in a high-temperature (200 °C) distributed control environment. Patented high-temperature techniques facilitate designs in a conventional, low-cost, 0.5-micron bulk CMOS foundry process. The HHT104 eight-channel instrumentation IC measures LVDTs, RTDs, thermocouples, and other sensors with up to 12-bit resolution. Dual sigma-delta converters and independent, programmable gain allow simultaneous conversion of two differential-output sensors. A stimulus driver may be used to drive bridge sensors with AC excitation and a temperature-stabilized oscillator provides 1.5- and 24-MHz system clocks for microprocessor use. The HHT212 current driver IC may be used to control two motors in full-bridge configuration or four independent half-bridge loads. Each channel is capable of driving up to 300 mA with 12-bit resolution. An internally-generated, temperature-stabilized current reference minimizes external components. The output current is programmed using a SPI serial interface, and the chip has built-in over-current and over-temperature protection. The HHT250 is a quad load driver featuring an integrated PWM controller, push-pull outputs and flexible drive capability. The HHT300 quad-output switched-mode power supply IC implements a compact power solution for multi-voltage microprocessors, sensors, and actuators. The external part count is minimized using integrated output FETs and a novel voltage feedback topology. Synchronous rectification reduces power dissipation and improves current capacity. Each channel has a pin-programmable output voltage and may be independently enabled for power supply sequencing. A high-temperature development system has been created using the four ICs and a DSP for actuator controller prototypes. A reference application was implemented using this system to drive a torque motor using LVDT position feedback.