Digital Input Hi-Fi Class D Headphone Amplifier LSI with the Industry's Lowest Power Consumption

ROHM has completed development of a digital input Hi-Fi class-D headphone amplifier LSI designed specifically for portable audio devices such as MP3 players, IC recorders, electronic dictionaries, digital cameras and notebook PCs. The BU7839GVW features the lowest power consumption in the industry and supports digital input without the need for a DAC by integrating a conversion circuit, resulting in longer battery life and playback time. Power consumption is 6.5mW - 85% less than the previous model, and mounting area is decreased by 40% due to the compact 4mm BGA package. A startup noise reduction circuit and muting transistor is built in, eliminating popping noises during startup. In addition, a special circuit is integrated that suppresses clicking sounds during volume adjustment and can be set to change the gain modification method between three modes: instant, zero cross and soft switching, for improved playback fidelity. (Sample price: 8.5US$)

· Main Features of BU7839GVW

1. Stereo audio DAC and headphone amp functionality on a single chip
2. Digital audio input compatibility reduces power consumption for longer playback time
3. Built in startup noise reduction circuit and muting transistor reduces popping noise during power ON/OFF
4. Integrated independent L-channel and R-channel digital volume control with three gain switching modes: instant, zero-cross and soft switch suppresses clicking noise during volume adjustment
5. PLL built in for Master/Slave compatibility
6. Compact SBGA024W040 package
7. Direct connection to DSP possible, reducing circuit size along with costs

· Glossary

• Class-D Amplifier
  A type of digital amplifier that changes the rectangular output using only H and L signals, resulting in better efficiency, reduced power consumption, smaller size and less costs than class AB amplifiers, making it ideal for portable audio devices.
• DAC (Digital to Analog Converter)
  A device or circuit that converts digital signals to analog signals. When amplifying an audio signal in a Class A or AB analog headphone amp, a DAC is needed between the DSP in the previous stage.
• DSP (Digital Signal Processor)
  A semiconductor chip that processes digitized signals (in this case, audio signals recorded on a DVD or flash memory), the DSP is capable of processing vast amounts of simple data, including compressing/expanding digital audio signals, adjusting the playback volume or speed, or controlling the gain.
• Register
  A circuit block that temporarily stores data for a particular operation (calculation). In this case the register refers to the memory area incorporated in the LSI for storing instruction commands or settings to be sent to the class-D headphone amp.
• Master/Slave function
  The Master supplies the clock signal to other systems or devices (Slave)
• PLL (Phased Locked Loop)
  Generates a signal synchronized with the input signal by detecting the phase difference between the input and output signals and controlling the VCO loop (Voltage Control Oscillator).
• Instant switching
  Instantly changes the gain by adjusting the gain setting register, although a loud click is generated.
  
• Zero cross point switching
  Changes the gain once the output signal reaches the zero cross point.
  
• Soft switching
  Changes the gain 1dB at a time at a particular interval (which can be set in the register) once the gain setting register is adjusted. Although the clicking volume is reduced, it takes more time to attain the desired gain.
  

	Digital Input Hi-Fi Class D Headphone Amplifier LSI