NAU88L21 Datasheet Rev1.8 Page 3 of 67 April, 2020
Table of Contents
BLOCK DIAGRAM : QFN32 ........................................................................ 2
PIN DIAGRAM : ............................................................................................ 5
PIN DESCRIPTION ...................................................................................... 6
ELECTRICAL CHARACTERISTICS............................................................ 7
1. GENERAL DESCRIPTION .................................................................. 10
1.1 Inputs ............................................................................................................... 10
1.2 Outputs ............................................................................................................ 10
1.3 ADC, DAC and Digital Signal Processing ........................................................ 10
1.4 Digital Interfaces .............................................................................................. 10
2. POWER SUPPLY ................................................................................ 11
2.1 Power on and off reset..................................................................................... 11
3. INPUT PATH DETAILED DESCRIPTIONS ........................................ 12
3.1 Analog Microphone Inputs ............................................................................... 12
3.2 Digital Microphone Input .................................................................................. 13
3.3 VREF ............................................................................................................... 13
3.4 MIC Bias .......................................................................................................... 14
3.5 MIC detect ....................................................................................................... 14
3.5.1 Key Release ................................................................................................................................. 16
4. ADC DIGITAL BLOCK ........................................................................ 17
4.1 ADC Dynamic Range Compressors (DRC) ..................................................... 17
4.1.1 Level Estimation............................................................................................................................ 17
4.1.2 Static Curve .................................................................................................................................. 18
4.2 ADC Digital Volume Control ............................................................................ 19
4.3 ADC Programmable Biquad Filter ................................................................... 19
4.4 Companding .................................................................................................... 20
4.5 Additional ADC Application Notes ................................................................... 20
5. DAC DIGITAL BLOCK ........................................................................ 21
5.1 DAC Dynamic Range Control (DRC) ............................................................... 21
5.1.1 Level Estimation............................................................................................................................ 21
5.1.2 Static Curve .................................................................................................................................. 22
5.2 DAC Digital Volume Control, Mute and Channel selection .............................. 23
5.3 DAC Soft Mute ................................................................................................. 23
5.4 DAC Auto Attenuate ........................................................................................ 23
5.5 DAC Path Digital Mixer with Side tone............................................................. 23
5.6 Companding .................................................................................................... 25
5.6.1 µ-law ............................................................................................................................................ 25
5.6.2 A-law ............................................................................................................................................ 25
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