Wolfgang Scherr

Ultra low-power monolithically integrated, capacitive pressure sensor for tire pressure monitoring

Tire pressure monitoring systems (TPMS) are gaining importance due to improved security standards in the automotive industry. In active systems, the power consumption of the system is of utmost importance for a required lifetime of more than 10 years. The presented integrated circuit comprises high resolution pressure, temperature and voltage monitoring, low-power oscillators, a specialized DSP with RAM/ROM and an EEPROM to store calibration data. The continuously running low-power oscillator for internal wake-up timing is operated with 30 nA. Due to the extremely low-power consumption of all circuit blocks, pressure measurements can be carried out in short intervals (0.5 s). This enables the implementation of a new intelligent dynamic wake-up algorithm to optimize the power-intensive HF-transmission intervals under different driving situations. Thus additional rotation detectors are not needed any more. The charge consumption without HF-transmission results in 48 mAh in 10 years.

An Integrated Hall Sensor Platform Design for Position, Angle and Current Sensing

A new platform design of a Hall sensor uses digital signal processing and digital 3rd order temperature compensation. The improved architecture of the front-end achieves low noise of <2 muT in a bandwidth of 400 Hz by using a 3rd-order multibit continuous-time DeltaSigma-ADC. By chopping the first stage of this ADC a low magnetic offset of <50 muT is realized in a typical automotive operating temperature range from -50 to 150degC. A novel circuit technique for a stress sensor is used to compensate stress and aging effects in the Hall sensor. All required digital calculations are done at low power and area with a new intelligent state machine, which also provides various digital interface protocols.

A miniature digital current sensor with differential Hall probes using enhanced chopping techniques and mechanical stress compensation

A 10kHz bandwidth 50Amax current sensor using a Hall effect gradiometer without magnetic core provides 80kHz update rate with a digital interface. Very low un-calibrated offset of 30mA (1σ) and after calibration typical 10mA over temperature is accomplished by a chopped multi-bit feedback continuous-time 3rd order ΔΣ-ADC. This also realizes low noise of 13mArms in 1kHz signal bandwidth. The ADC uses enhanced chopping techniques and additional digital feedback loops to avoid chopper ripple. New analog and digital stress-compensation circuits with lateral and vertical n-doped resistors achieve lifetime gain drifts below 1% and temperature compensation. Auto-zeroing ping-pong comparators offer a fast over-current detection of 1...2μs on a dedicated output pin. The monolithic integrated sensor chip and the 4kV galvanic isolated current rail fit into a very small 7×7×1mm3 package.

An Integrated Magnetic Sensor with Two Continuous-Time /spl Delta//spl Sigma/-Converters and Stress Compensation Capability

A linear 4kHz Hall sensor in 0.6mum BiCMOS has digital 3rd-order temperature compensation, a DR of 90dB and an offset of 50muT. It uses a chopped 3rd-order multibit CT-DeltaSigma ADC including an up/down counter loop and bandgap-based compensation for stability and accuracy. Digital compensation of sensitivity drift caused by package-induced stress is provided