DESCRIPTION
The WM8940 is a low power, high quality mono CODEC designed for portable applications such as digital still cameras or camcorders.
The device integrates support for a differential or single ended mic, and includes drivers for speakers or headphone, and mono line output. External component requirements are reduced as no separate microphone or headphone amplifiers are required.
Advanced Sigma Delta Converters are used along with digital decimation and interpolation filters to give high quality audio at sample rates from 8 to 48ks/s. A selectable high pass filter and four fully-programmable notch filters are available in the ADC path. An advanced mixed signal ALC function with noise gate is provided, while readback of PGA gain during ALC operation is supported. The digital audio interface supports A-law and -law companding.
An on-chip PLL is provided to generate the required Master Clock from an external reference clock. The PLL clock can also be output if required elsewhere in the system.
The WM8940 operates at supply voltages from 2.5 to 3.6V, although the digital supplies can operate at voltages down to 1.71V to save power. Different sections of the chip can also be powered down under software control using the selectable two or three wire control interface.
WM8940 is supplied in a very small 4x4mm QFN package, offering high levels of functionality in minimum board area, with high thermal performance.

FEATURES
• Mono CODEC:
• Audio sample rates:8, 11.025, 16, 22.05, 24, 32, 44.1, 48kHz
• DAC SNR 98dB, THD -84dB (‘A’-weighted @ 8 – 48ks/s)
• ADC SNR 94dB, THD -80dB (‘A’-weighted @ 8 – 48ks/s)
• On-chip Headphone/Speaker Driver
- 40mW output power into 16
- BTL speaker drive 0.4W into 8
• Additional MONO Line output
• Multiple analogue or ‘Aux’ inputs, plus analogue bypass path
• Mic Preamps:
• Differential or single end Microphone Interface
- Programmable preamp gain
- Pseudo differential inputs with common mode rejection
- Programmable ALC / Noise Gate in ADC path
• Low-noise bias supplied for electret microphones
OTHER FEATURES
• Digital Playback Limiter
• Programmable high pass filter (wind noise reduction)
• 4 notch filters (narrowband noise suppression)
• On-chip PLL
• Low power, low voltage
- 2.5V to 3.6V (digital: 1.71V to 3.6V)
• 4x4x0.9mm 24 lead QFN package

APPLICATIONS
• Digital still cameras and camcorders
• General purpose mono audio CODEC