98/95 dB Stereo Codec with Speaker Driver

The WM8978 is a low power stereo codec with integrated pre-amps for stereo differential mics and includes drivers for speakers, headphone and differential or stereo line output. External component requirements are reduced as no separate microphone or headphone amplifiers are required. Advanced on-chip digital signal processing includes a five-band equalizer, a mixed-signal automatic level control for the microphone or line input through the A/D converter, as well as a purely digital limiter function for record or playback. Additional digital filtering options are available in the ADC path to provide application filtering such as ‘wind noise reduction.’ The WM8978 codec can operate as a master or a slave. An internal PLL can generate all required audio clocks for the codec from common reference clock frequencies, such as 12 and 13 MHz. Individual sections of the chip can also be powered down under software control.

Technology

Mono/Stereo Codecs

Features

Stereo Codec:

  • DAC SNR 98 dB, THD -84 dB (’A’ weighted @ 48kHz)
  • ADC SNR 95 dB, THD -84 dB (’A’ weighted @ 48kHz)
  • On-chip headphone driver with ’capless’ option
  • 40mW output power into 16W / 3.3V SPKVDD
  • 1W output power into 8W BTL speaker / 5V SPKVDD
  • Capable of driving piezo speakers
  • Stereo speaker drive configuration

Mic Preamps:

  • Stereo differential or mono microphone interfaces
  • Programmable preamp gain
  • Psuedo-differential inputs with common mode rejection
  • Programmable ALC / noise gate in ADC path
  • Low-noise bias supplied for electret microphones

Other Features:

  • Enhanced 3-D function for improved stereo separation
  • Digital playback limiter
  • 5-band equalizer (record or playback)
  • Programmable ADC high pass filter (wind noise reduction)
  • Programmable ADC notch filter
  • Aux inputs for stereo analog input signals or beep
  • On-chip PLL supporting 12, 13, 19.2MHz and other clocks
  • Low power, low voltage
  • 2.5V to 3.6V (digital core: 1.62V to 3.6V)
  • 5x5mm 32-pin QFN package

Parametric Specifications

Channels In 2
Channels Out 2
DAC THD+N (dB) -84
ADC THD+N (dB) -84
Analog Power Supply (V) 2.5-3.6
Supply Current (µA) 1.71-3.6
Package 32 QFN

Technical Documents

WM8978 Product Datasheet

Oct 1, 2011, v4.5 : 1485 Kb

WM8978 6160 FL32 M REV1 Schematic and Layout

Oct 1, 2009, v1.1 : 1000 Kb

Design Resources

WAN_0197 Improving the PSRR in Wolfson CODECs

Jun 1, 2008, WAN0197 rev 1.0 : 130 Kb

WAN_0140 ALC for Portable Applications

Mar 1, 2007, WAN0140 rev 1.2 : 436 Kb

WAN_0178 Suggested ALC Settings for Portable Devices

Feb 1, 2007, WAN0178 rev 1.0 : 81 Kb

Software and Tools

Device Pack for WM8978EV1

v1.2 : 1349 Kb

WISCE Setup

v3.8.1.2 : 40.3 Mb

More

Comprehensive Solutions