Product category: Analogue and Mixed Signal ICs
News Release from: National Semiconductor | Subject: LM48555
Edited by the Electronicstalk Editorial Team on 01 June 2007
Audio amp powers up slimline ceramic
speakers
Audio power amplifier delivers the industry's highest voltage for driving ceramic speakers used in a wide range of 3V portable devices.
National Semiconductor has introduced a single-chip Boomer audio power amplifier that delivers the industry's highest voltage for driving ceramic speakers used in a wide range of 3V portable devices Driving the ceramic speaker at higher voltages allows it to produce a higher sound-pressure level (SPL) for applications that require louder sound
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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The LM48555 drives ceramic speakers in cellphones, smart-phones, notebook computers and other small handheld devices.
With a ceramic speaker load equivalent to 1uF at 20ohm, the LM48555 provides a voltage drive of 15.7V peak-to-peak with less than 1% total harmonic distortion plus noise (THD+N).
In addition, the LM48555's tiny 12-bump micro-SMD package has a footprint of 1.5 x 2.0mm, making it possible for manufacturers to create ultrathin feature-rich handsets.
Ceramic speakers require higher voltage, but less current compared with traditional moving coil speakers.
The primary benefits of ceramic speakers are their thin profile and light weight.
Voice coil speakers are typically 4mm or more in thickness, whereas ceramic speakers are only 0.7mm thick and often weigh less than 1g.
The LM48555 delivers 15.7V peak-to-peak from a 3V DC power supply, and typically offers low quiescent current of 7.5mA from a 5V supply.
The LM48555 can achieve additional battery savings with its low power shutdown mode, and its differential inputs improve noise rejection.
Power supply rejection ratio (PSRR) 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 minimises transient current during power-up.
The LM48555, available in a 12-bump thin micro-SMD package, is priced at US $1.95 each in 1000-unit quantities.
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