New Class D audio chipset cuts part count and cuts board size by half
4 April 2007
Analogue, Mixed Signal, LSI
International Rectifier has introduced a new Class D audio chipset comprised of the IRS20955 200 V digital audio driver IC and the IRFI4024Hx series of digital audio MOSFETs.
Compared to typical designs, it says the new IC reduces PCB board space by 50% for Class D audio amplifiers up to 500 W, while the MOSFETs reduce power switch part count of the Class D stage by 50% for the entire mid-voltage range of mid- and high-power amplifiers for applications such as home theatre applications, professional amplifiers, musical instruments and car entertainment.
Audio driver
The IRS20955(S)(TR)PBF IC reduces external component count by up to 27 components and features a unique floating, 3,3 V/5 V 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 optimise the over-current protection circuit. In addition, this offers considerable space-saving benefits with the elimination of a large current-sense resistor. Further, the IC has built-in protection control logic that eliminates 11 components and shrinks board footprint.
The new audio IC has preset internal deadtime generation to enable accurate and stable gate switch timing. This improves total harmonic distortion (THD) performance and noise immunity. Operating up to 800 kHz, the IRS20955 digital audio IC is also suitable for single-supply, full-bridge designs.
MOSFETs
In addition to low on-state resistance, IR's series of half-bridge N-channel MOSFETs provide optimised 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 mΩ for high efficiency, and a typical Qg of 8,9 nC and Qsw of 4,3 nC for improved THD.
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