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Audio chip does EMI filtering, ESD protection

Posted: 04 Jul 2008 ?? ?Print Version ?Bookmark and Share

Keywords:EMI filtering? ESD protection? handset audio?

For superior audio performance in feature-rich cellphones, the EMIF06-AUD01F2 from STMicroelectronics implements the complete EMI filtering and ESD protection for stereo headset output and external and internal microphones within a flip-chip package measuring 2.42mm x 1.92mm.

The EMIF06-AUD01F2 eliminates audible handset demodulation noise, or 'bumble-bee' noise, by achieving -25dB attenuation (S21) throughout the stop-band 800-2480MHz using high-density 1.3nF PZT (lead, zirconate titanate) capacitors on the microphone lines. The device also achieves high ESD protection through the combination of integrated TVS (transient voltage suppressor) diodes, low-inductance packaging, and the Z-R-Z pi-filter topology.

As the first device to combine filtering and ESD protection for all handset speaker and microphone channels, the EMIF06-AUD01F2 saves more than 50 percent of board space compared to previous integrated solutions using two ICs with external resistors, and up to 77 percent compared to alternative discrete solutions. All necessary biasing circuitry is also integrated, as well as a 10 series resistor in the speaker output, thereby minimizing external components. The low package profile of 0.65mm also helps designers implement high functionality within cutting-edge, ultraslim handset styles.

The space-saving advantages are combined with better audio performance and higher ESD protection compared to integrated or discrete alternatives. The integrated TVS diodes have a 20V peak clamping voltage, enabling the device to meet IEC61000-4-2 level 4 ESD protection at the external pins. Total harmonic distortion (THD) is less than -75dB, while the device achieves high audio-power transfer by delivering 135mA per speaker channel ensuring excellent sound reproduction. This is achieved thanks to the high thermal efficiency of the wafer-level flip-chip package, which supports 285mW total continuous power dissipation.

The EMIF06-AUD01F2 is already in volume production and is available at 55 cents for 1,000 pieces.

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