Eric Gaalaas

Integrated stereo /spl Delta//spl Sigma/ class D amplifier

A 2/spl times/40 W class D amplifier chip is realized in 0.6-/spl mu/m BCDMOS technology, integrating two delta-sigma (/spl Delta//spl Sigma/) modulators and two full H-bridge switching output stages. Analog feedback from H-bridge outputs helps achieve 67-dB power supply rejection ratio, 0.001% total harmonic distortion, and 104-dB dynamic range. The modulator clock rate is 6 MHz, but dynamically adjusted quantizer hysteresis reduces output data rate to 450 kHz, helping achieve 88% power efficiency. At AM radio frequencies, the modulator output spectrum contains a single peak, but is otherwise tone-free, unlike conventional pulse-width modulation (PWM) modulators which contain energetic tones at harmonics of the PWM clock frequency.

Integrated stereo delta-sigma class D amplifier

A 2/spl times/40W (into 4/spl Omega/ with a 20V supply) integrated stereo /spl Delta//spl Sigma/ class D amplifier with 100dB SNR is realized in a 0.6 /spl mu/m CMOS process with DMOS transistors and buried Zener diodes. Feedback from power stage outputs gives 0.001% THD and 65dB PSRR. The modulator clock rate is 6MHz, but dynamically adjusted quantizer hysteresis reduces the output data rate to 450kHz, helping achieve 88% efficiency.

A 20-W stereo class-D audio output power stage in 0.6-/spl mu/m BCDMOS technology

This paper presents a highly power efficient 2/spl times/20-W class-D audio output power stage implemented in 0.6-/spl mu/m BCDMOS technology. The presented power stage is capable of driving 2/spl times/8-/spl Omega/ loads from a 20-V power supply at a power efficiency approaching 90%. Circuit details of thermal detection, over-current protection, and startup speaker click/pop are also presented. The performance of open-loop Class-D output stages are limited by the distortion mechanisms present within the power stage itself. A third-order PWM modulator was prototyped and used to dramatically improve the performance of the Class-D output stage by using feedback. The results of this work are also presented.

A transformer-based digital isolator with 20kVPK surge capability and > 200kV/µS Common Mode Transient Immunity

This paper presents a transformer-based digital isolator that achieves best-in-class robustness with 20kVPK surge capability and > 200kV/μS Common Mode Transient Immunity (CMTI). Using polyimide as insulation material, the isolation barrier is more than 30μm thick and enables the exceptional surge performance. The transformer is fully differential with symmetric layout to improve noise immunity. The OOK Transmitter (TX) is based on the negative-Gm oscillator and operates in the voltage-limited domain. It enable the TX to keep generating the differential On-Off Keying (OOK) carrier signal during disturbances from very fast Common Mode Transient (CMT) noise.