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Power amp drives ceramic speaker at higher voltages

Posted: 01 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:power amps? ceramic speaker drivers? audio power amplifier?

National Semiconductor Corp. has developed what it touts as the industry's most powerful ceramic speaker driver, the LM48555. The single-chip Boomer audio power amplifier is said to deliver the highest voltage for driving ceramic speakers used in a wide range of 3V portable devices. The LM48555 drives ceramic speakers in cellphones, smartphones, laptops and other small handheld devices.

Driving the ceramic speaker at higher voltages allows it to produce a higher sound-pressure level for applications that require louder sound, said National Semiconductor. With a ceramic speaker load equivalent to 1?F + 20?, the LM48555 provides a voltage drive of 15.7V peak-to-peak with less than 1 percent total harmonic distortion plus noise (THD+N). In addition, the LM4855's tiny 12-bump micro SMD package offers a 1.5 x 2mm footprint, making it possible for manufacturers to develop ultrathin, feature-rich handsets.

The LM48555 delivers 15.7V peak-to-peak from a 3Vdc power supply and typically offers low quiescent current of 7.5mA from a 5V supply. It can achieve additional battery savings with its low power shutdown mode, and its differential inputs improve noise rejection.

Power supply rejection ratio is typically 80dB at 217Hz. The LM48555 does not require bootstrap capacitors or snubber circuits. The amplifier's advanced "pop-and-click" circuitry eliminates noise that typically occurs during turn-on and turn-off transitions. The LM48555's integrated boost regulator features a soft start function that minimizes transient current during power-up.

Pricing begins at $1.95 each in quantities of 1,000.

- Gina Roos

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