'Filtering' related articles 1

  1. 2008/01/05 WM8741 - 24-bit 192kHz DAC with Advanced Digital Filtering
The WM8741 is a very high performance stereo DAC designed for audio applications such as professional recording systems, A/V receivers and high specification CD, DVD and home theatre systems. The device supports PCM data input word lengths from 16 to 32-bits and sampling rates up to 192kHz. The WM8741 also supports DSD bitstream data format, in both direct DSD and PCM-converted DSD modes.
The WM8741 includes fine resolution volume and soft mute control, digital de-emphasis and a range of advanced digital filter responses, followed by a digital interpolation filter, multi-bit sigma delta modulator and stereo DAC. Wolfson’s patented architecture optimises the linearity of the DAC and provides maximum insensitivity to clock jitter.
The digital filters include several selectable roll-off and performance characteristics. The user can select between standard sharp or slow roll-off responses. In addition, the WM8741 includes a selection of advanced digital filter characteristics including non-half band filters and minimum phase filters. This flexibility provides a range of benefits, such as significantly reduced pre-ringing and minimal group delay. The internal digital filters can also be by-passed and the WM8741 used with an external digital filter.
The WM8741 supports two connection schemes for audio DAC control. The 2/3 wire serial control interface provides access to all features. A range of features can also be accessed by hardware control interface.
The WM8741 is available in a convenient 28-SSOP package, and is pin compatible with the WM8740.

• Advanced Ultra High Performance Multi-bit Sigma-Delta Architecture
− 128dB SNR (‘A’-weighted mono @ 48kHz)
− 125dB SNR (‘A’-weighted stereo @ 48kHz)
− 123dB SNR (non-weighted stereo @ 48kHz)
− -100dB THD @ 48kHz
− Differential analogue voltage outputs
− High tolerance to clock jitter
• PCM Mode
− Sampling frequency: 32kHz to 192kHz
− Input data word length support: 16 to 32-bit
− Supports all standard audio interface formats
− Selectable advanced digital filter responses
− Includes linear/minimum phase and range of tailored characteristics
− Enables low pre-ringing, minimal latency
− Optional interface to industry standard external filters
− Digital volume control in 0.125dB steps with soft ramp and soft mute
− Anti-clipping mode to prevent distortion even with input signals recorded up to 0dB
− Selectable de-emphasis support
− Zero Flag output
• DSD Mode
− DSD bit-stream support for SACD applications
− Support for normal or phase modulated bit-streams
− Direct or PCM converted DSD paths (DSD Plus)
− DSD mute
• Hardware or software control modes:
− 2 and 3 wire serial control interface support
• Pin compatible with WM8740
• 4.5V to 5.5V analogue, 3.0V to 3.6V digital supply operation
• 28-lead SSOP Package

• Professional audio systems
• CD, DVD, SACD audio
• Home theatre systems
• A/V receivers


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