Class D Audio Chipset Cuts Part Count and Board Size by 50%

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International Rectifier has introduced a new Class D audio chipset comprised of the IRS20955 200V digital audio driver IC and the IRFI4024Hx series of digital audio MOSFETs. Compared to typical designs, the new IC reduces PCB board space by 50 percent for Class D audio amplifiers up to 500W, while the MOSFETs reduce power switch part count of the Class D stage by 50 percent for the entire mid-voltage range of mid- and highpower amplifiers for home theater applications, professional amplifiers, musical instruments and car entertainment.

“The IRS20955 IC delivers higher performance, protection and efficiency in the compact form factor required for ever-shrinking Class D audio designs,” said Stephane Ernoux, product manager for IR’s Class D audio products. “When combined with the our 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,” he added.

The IRS20955(S)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 new 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 800kHz, the IRS20955 digital audio IC is also suitable for single supply, full-bridge designs.

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 48MΩ for high efficiency, and a typical Q_g of 8.9nC and Q_sw of 4.3nC for improved THD.

 

FEATURES Floating PWM input enables easy half-bridge implementation Programmable bi-directional over current protection with self reset function Programmable preset deadtime for improved THD performances High noise immunity ±100V ratings deliver up to 500W in output power 3.3V/5V logic compatible input Operates up to 800kHz RoHS-compliant

APPLICATIONS Home theater applications Professional amplifiers Musical instruments Car entertainment

 

 

IRS20955 Specifications

Part Number	Package	VOFFSET	Selectable Deadtime	Propagation Delay	OC Protection Delay
IRS20955PBF	DIP-16	0 - 200V	15/25/35/45ns	90ns	500ns
IRS20955SPBF	SO16N	0 - 200V	15/25/35/45ns	90ns	500ns

 

 

IRFI4024H Specifications

Part Number	Package	Vds	Rds(on) typ	Qg typ	Qsw typ
IRFI4024H-117P	TO-220FP 5P	55V	48MΩ	8.9 nC	4.3 nC
IRFI4212H-117P	TO-220FP 5P	100V	58MΩ	12 nC	6.9 nC
IRFI4019H-117P	TO-220FP 5P	150V	80MΩ	13 nC	4.1 nC
IRFI4020H-117P	TO-220FP 5P	200V	80MΩ	19 nC	6.8 nC

 

 

IRAUDAMP4

The IRAUDAMP4 reference design is an example of a two-channel 120W half-bridge Class D audio power amplifier. The reference design will demonstrate how to use the IRS20955, implement protection circuits, and design an optimum PCB layout using the IRF6645 DirectFET MOSFETs. The resulting design requires no heatsink for normal operation (one-eighth of continuous rated power). The reference design contains all the required housekeeping power supplies for ease of use. The two-channel design is scalable, for power and the number of channels.

 

FEATURES Output power: 120W x two channels Total Harmonic Distortion (THD) = 1%, 1kHz Residual noise: 52µV, IHF-A weighted, AES-17 filter Distortion: 0.004% THD+N @ 60W, 4Ω Efficiency: 96% @ 120W, 4Ω, single-channel driven, Class D stage Multiple protection features: Over current protection (OCP) Over voltage protection (OVP) Under voltage protection (UVP) DC protection (DCP) Over temperature protection (OTP) PWM modulator: Self oscillating half-bridge topology with optional clock synchronization

APPLICATIONS AV receivers Home theater systems Mini component stereos Sub-woofers

 

 

 Featured Products

Part Number		Description	Data Sheet	App. Notes
IRAUDAMP4		Two-channel 120W Half-bridge Class-D Audio Power Amplifier
IRFI4019H-117P		150V Dual N-Channel Digital Audio HEXFET Power MOSFET
IRFI4020H-117P		200V Dual N-Channel Digital Audio HEXFET Power MOSFET
IRFI4024H-117P		55V Dual N-Channel Digital Audio HEXFET Power MOSFET
IRFI4212H-117P		100V Dual N-Channel Digital Audio HEXFET Power MOSFET
IRS20955PBF		Protected Digital Audio Driver with Floating PWM Input
IRS20955SPBF		Protected Digital Audio Driver with Floating PWM Input

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