International Rectifier has introduced a Class D audio chipset comprised of the IRS20955 200V digital audio driver IC and the IRFI4024Hx series of digital audio MOSFETs. The chipset is dedicated to entire mid-voltage range of mid- and high-power amplifiers for home theatre applications, professional amplifiers, musical instruments and car entertainment. When combined with IR’s Class D audio driver IC, the new integrated half-bridge digital audio MOSFETs provide a scalable solution to enhance performance and sound quality while cutting the power switch part count in half.

IRS20955 Technical Data

The IRS20955(S)(TR)PBF IC reduces external component count by up to 27 components and features a unique floating, 3.3V/5V logic-compatible, PWM input that eliminates seven external level-shift components for Class D audio applications using a half-bridge topology and dual power supply. Greater protection is achieved with an integrated programmable bi-directional current-sensing feature with self-reset function that allows the high-voltage IC to sense the exact point of the switching cycle. Current is sensed at the correct moment allowing the IC to optimize the over-current protection circuit. In addition, this offers considerable space-saving benefits with the elimination of a large current-sense resistor. The IC has built-in protection control logic that eliminates 11 components and shrinks board footprint, compared to existing audio IC reference designs. The audio IC has preset internal deadtime generation to enable accurate and stable gate switch timing, while delivering optimum deadtime settings for improved total harmonic distortion (THD) performance and high noise immunity. In addition to simplifying design, this deadtime feature reduces part count by as much as eight external components, and reduces board space by eliminating large package types. Operating up to 800 kHz, the IRS20955 digital audio IC is also suitable for single-supply, full-bridge designs.

IRFI4024Hx Technical Data

In addition to low on-state resistance, the series of half-bridge N-channel MOSFETs provide optimized gate charge, body-diode reverse recovery and internal gate resistance to improve key Class D audio amplifier performance parameters such as efficiency, THD and EMI. For example, the IRFI4024H-117P features a typical RDs(on) of 48 mOhms for high efficiency, and a typical Qg of 8.9nC and Qsw of 4.3nC for improved THD.