LM4981 Datasheet | National Semiconductor

Description The LM4981 is a stereo, ground-referenced, output capacitor-less headphone amplifier capable of delivering 83m W of continuous average power into a 16Ω load with less than 1% THD+N while operating from a single 3V supply. The LM4981 features a new circuit technology that utilizes a charge pump to generate a negative reference voltage. This allows the outputs to be biased about ground, thereby eliminating output-coupling capacitors typically used with normal single-ended loads. The LM4981 provides high quality audio reproduction with minimal external ponents. A ground referenced output eliminates the output coupling capacitors typically required to drive single-ended loads such as headphones. The ground reference architecture reduces ponents count, cost and board space consumption, making the LM4981 ideal for handheld MP3 players, mobile phones and other portable equipment where board space is at a premium. Eliminating the output capacitors also improves low frequency response. The LM4981 operates from a single 2.0V - 4.2V supply, and features a 2-wire, up/down volume control that sets the gain of the amplifier between -33d B to +12d B in 16 discrete steps. Selectable (active high/low) low power shutdown mode provides flexible shutdown control. Superior click and pop suppression eliminates audible transients during start-up and shutdown. The LM4981 features an Automatic Standby Mode circuitry (patent pending). In the absence of an input signal, after approximately 12 seconds, the LM4981 goes into low current standby mode. The LM4981 recovers into full power operating mode immediately after a signal is applied to either the left or right input pins. This feature saves power supply current in battery operated applications. Key Specifications j Improved PSRR at 217Hz j THD+N at 1k Hz, 50m W 67d B (typ) 1.0% (typ) 2.0 to 4.2V 83m W (typ) 0.01µA (typ) into 32Ω SE (3V) j Single Supply Operation (VDD) j Power Output at VDD = 3V, RL = 16Ω, THD ≤ 1% j Shutdown...