w WM8950 ADC with Microphone Input and Programmable Digital Filters DESCRIPTION FEATURES The WM8950 is a low power, high quality mono ADC designed for portable applications such as Digital Still Camera, Digital Voice Recorder or games console accessories. * * * * * * The device integrates support for a differential or single ended mic. External component requirements are reduced as no separate microphone amplifiers are required. Advanced Sigma Delta Converters are used along with digital decimation filters to give high quality audio at sample rates from 8 to 48ks/s. Additional digital filtering options are available, to cater for application filtering such as wind noise reduction, noise rejection, plus an advanced mixed signal ALC function with noise gate is provided. 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 WM8950 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 by way of the selectable two or three wire control interface. WM8950 is supplied in a very small 4x4mm QFN package, offering high levels of functionality in minimum board area, with high thermal performance. * Mono ADC: Audio sample rates:8, 11.025, 16, 22.05, 24, 32, 44.1, 48kHz SNR 94dB, THD -83dB (`A'-weighted @ 8 - 48ks/s) Multiple auxiliary analog inputs 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 * 5 band EQ * Programmable High Pass Filter (wind noise reduction) * Fully Programmable IIR Filter (notch filter) * On-chip PLL * Low power, low voltage - 2.5V to 3.6V (digital: 1.71V to 3.6V) - power consumption 10mA all-on 48ks/s mode * 4x4x0.9mm 24 lead QFN package APPLICATIONS * * * * WOLFSON MICROELECTRONICS plc To receive regular email updates, sign up at http://www.wolfsonmicro.com/enews/ Digital Still Camera General Purpose low power audio ADC Games console accessories Voice recorders Production Data, January 2008, Rev 4.2 Copyright (c)2008 Wolfson Microelectronics plc WM8950 Production Data TABLE OF CONTENTS DESCRIPTION .......................................................................................................1 FEATURES.............................................................................................................1 APPLICATIONS .....................................................................................................1 TABLE OF CONTENTS .........................................................................................2 PIN CONFIGURATION...........................................................................................3 ORDERING INFORMATION ..................................................................................3 RECOMMENDED OPERATING CONDITIONS .....................................................5 ELECTRICAL CHARACTERISTICS ......................................................................6 TERMINOLOGY ............................................................................................................ 7 SIGNAL TIMING REQUIREMENTS .......................................................................8 SYSTEM CLOCK TIMING ............................................................................................. 8 AUDIO INTERFACE TIMING - MASTER MODE .......................................................... 8 AUDIO INTERFACE TIMING - SLAVE MODE.............................................................. 9 CONTROL INTERFACE TIMING - 3-WIRE MODE .................................................... 10 CONTROL INTERFACE TIMING - 2-WIRE MODE .................................................... 11 DEVICE DESCRIPTION.......................................................................................12 INTRODUCTION ......................................................................................................... 12 INPUT SIGNAL PATH ................................................................................................. 13 ANALOGUE TO DIGITAL CONVERTER (ADC).......................................................... 18 INPUT AUTOMATIC LEVEL CONTROL (ALC) ........................................................... 21 DIGITAL AUDIO INTERFACES................................................................................... 38 AUDIO SAMPLE RATES ............................................................................................. 43 MASTER CLOCK AND PHASE LOCKED LOOP (PLL) ............................................... 43 GENERAL PURPOSE INPUT/OUTPUT...................................................................... 45 CONTROL INTERFACE.............................................................................................. 46 RESETTING THE CHIP........................................................................................47 POWER SUPPLIES .................................................................................................... 47 ADC POWER UP/DOWN SEQUENCE ....................................................................... 48 POWER MANAGEMENT ............................................................................................ 49 REGISTER MAP...................................................................................................50 DIGITAL FILTER CHARACTERISTICS ...............................................................51 TERMINOLOGY .......................................................................................................... 51 ADC FILTER RESPONSES .................................................................................52 DE-EMPHASIS FILTER RESPONSES........................................................................ 53 HIGHPASS FILTER..............................................................................................54 5-BAND EQUALISER .................................................................................................. 55 APPLICATIONS INFORMATION .........................................................................59 RECOMMENDED EXTERNAL COMPONENTS .......................................................... 59 PACKAGE DIAGRAM ..........................................................................................60 IMPORTANT NOTICE ..........................................................................................61 ADDRESS ................................................................................................................... 61 w PD Rev 4.2 January 2008 2 WM8950 Production Data PIN CONFIGURATION TOP VIEW ORDERING INFORMATION ORDER CODE TEMPERATURE RANGE PACKAGE MOISTURE SENSITIVITY LEVEL PACKAGE BODY TEMPERATURE WM8950GEFL/V -25C to +85C 24-lead QFN (4x4x0.9mm) (Pb-free) MSL3 260oC WM8950GEFL/RV -25C to +85C 24-lead QFN (4x4x0.9mm) (Pb-free, tape and reel) MSL3 260oC Note: Reel Quantity = 3,500 w PD Rev 4.2 January 2008 3 WM8950 Production Data PIN DESCRIPTION PIN NO NAME TYPE DESCRIPTION 1 MICBIAS Analogue Output Microphone bias 2 AVDD Supply 3 AGND Supply Analogue ground (feeds ADC) 4 DCVDD Supply Digital core supply 5 DBVDD Supply Digital buffer (input/output) supply 6 DGND Supply Digital ground 7 ADCDAT Digital Output 8 TP Test Pin 9 FRAME Digital Input / Output ADC sample rate clock or frame synch 10 BCLK Digital Input / Output Digital audio bit clock 11 MCLK Digital Input 12 CSB/GPIO Digital Input / Output 13 SCLK Digital Input 14 SDIN Digital Input / Output 15 MODE Digital Input 16 DNC Do not connect Leave this pin floating 17 DNC Do not connect Leave this pin floating 18 AGND2 Supply 19 DNC Do not connect 20 AVDD2 Supply 21 AUX Analogue Input Analogue supply (feeds ADC) ADC digital audio data output Connect to ground Master clock input 3-Wire MPU chip select or general purpose input/output pin. 3-Wire MPU clock Input / 2-Wire MPU Clock Input 3-Wire MPU data Input / 2-Wire MPU Data Input Control interface mode selection pin. Analogue ground Leave this pin floating Analogue supply Auxiliary analogue input 22 VMID Reference 23 MICN Analogue Input Decoupling for midrail reference voltage Microphone negative input 24 MICP Analogue Input Microphone positive input (common mode) Note: It is recommended that the QFN ground paddle should be connected to analogue ground on the application PCB. w PD Rev 4.2 January 2008 4 WM8950 Production Data ABSOLUTE MAXIMUM RATINGS Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously operating at or beyond these limits. Device functional operating limits and guaranteed performance specifications are given under Electrical Characteristics at the test conditions specified. ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage of this device. Wolfson tests its package types according to IPC/JEDEC J-STD-020B for Moisture Sensitivity to determine acceptable storage conditions prior to surface mount assembly. These levels are: MSL1 = unlimited floor life at <30C / 85% Relative Humidity. Not normally stored in moisture barrier bag. MSL2 = out of bag storage for 1 year at <30C / 60% Relative Humidity. Supplied in moisture barrier bag. MSL3 = out of bag storage for 168 hours at <30C / 60% Relative Humidity. Supplied in moisture barrier bag. The Moisture Sensitivity Level for each package type is specified in Ordering Information. CONDITION MIN DBVDD, DCVDD, AVDD, AVDD2 supply voltages MAX -0.3V +4.2 Voltage range digital inputs DGND -0.3V DVDD +0.3V Voltage range analogue inputs AGND -0.3V AVDD +0.3V -25C +85C Operating temperature range, TA Storage temperature prior to soldering 30C max / 85% RH max Storage temperature after soldering -65C +150C Notes 1. Analogue and digital grounds must always be within 0.3V of each other. 2. All digital and analogue supplies are completely independent from each other. RECOMMENDED OPERATING CONDITIONS PARAMETER SYMBOL Digital supply range (Core) DCVDD 1.711 3.6 Digital supply range (Buffer) DBVDD 1.71 3.6 V AVDD, AVDD2 2.5 3.6 V Analogue supplies range Ground DGND, AGND, AGND2 TEST CONDITIONS MIN TYP 0 MAX UNIT V V Notes 1. When using PLL, DCVDD must be 1.9V or higher. 2. AVDD must be DBVDD and DCVDD. 3. DBVDD must be DCVDD. 4. When using PLL, DCVDD must be 1.9V. w PD Rev 4.2 January 2008 5 WM8950 Production Data ELECTRICAL CHARACTERISTICS Test Conditions DCVDD = 1.8V, AVDD = DBVDD = 3.3V, SPKVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, 24-bit audio data unless otherwise stated. PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Microphone Inputs (MICN, MICP) Full-scale Input Signal Level (Note 1) - note this changes with AVDD Mic PGA equivalent input noise VINFS PGABOOST = 0dB INPPGAVOL = 0dB At 35.25dB gain 1.0 0 Vrms dBV 150 uV k Input resistance RMICIN Gain set to 35.25dB 1.6 Input resistance RMICIN Gain set to 0dB 47 k Input resistance RMICIN Gain set to -12dB 75 k Input resistance RMICIP (Constant for all gain settings) 94 k Input Capacitance CMICIN 10 pF MIC Input Programmable Gain Amplifier (PGA) Programmable Gain -12 Programmable Gain Step Size Guaranteed monotonic Mute Attenuation 35.25 dB 0.75 dB 108 dB Selectable Input Gain Boost (0/+20dB) Gain Boost 0 20 dB dB Automatic Level Control (ALC)/Limiter Target Record Level -28.5 -6 Programmable Gain -12 35.25 Programmable Gain Step Size dB Guaranteed Monotonic 0.75 dB Gain Hold Time (Note 2) tHOLD MCLK=12.288MHz (Note 4) 0, 2.67, 5.33, 10.67, ... , 43691 (time doubles with each step) ms Gain Ramp-Up (Decay) Time (Note 3) tDCY ALCMODE=0 (ALC), MCLK=12.288MHz (Note 4) 3.3, 6.6, 13.1, ... , 3360 (time doubles with each step) ms ALCMODE=1 (limiter), MCLK=12.288MHz (Note 4) 0.73, 1.45, 2.91, ... , 744 (time doubles with each step) ALCMODE=0 (ALC), MCLK=12.288MHz (Note 4) 0.83, 1.66, 3.33, ... , 852 (time doubles with each step) ALCMODE=1 (limiter), MCLK=12.288MHz (Note 4) 0.18, 0.36, 0.73, ... , 186 (time doubles with each step) Gain Ramp-Down (Attack) Time (Note 3) tATK ms Analogue to Digital Converter (ADC) Signal to Noise Ratio (Note 5, 6) Total Harmonic Distortion + Noise (Note 6) THD+N A-weighted, 0dB PGA gain 85 94 dB -1dBFS input 0dB PGA gain -75 -83 dB 1.0 0 Vrms dBV 20 k 10 pF Auxiliary Analogue Input (AUX) Full-scale Input Signal Level (0dB) - note this changes with AVDD VINFS Input Resistance RAUXIN Input Capacitance CAUXIN w AUXMODE=0 PD Rev 4.2 January 2008 6 WM8950 Production Data Test Conditions DCVDD = 1.8V, AVDD = DBVDD = 3.3V, SPKVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, 24-bit audio data unless otherwise stated. PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT Microphone Bias Bias Voltage (MBVSEL=0) VMICBIAS 0.9*AVDD V Bias Voltage (MBVSEL=1) VMICBIAS 0.65*AVDD V Bias Current Source IMICBIAS Output Noise Voltage Vn 3 1K to 20kHz 15 mA nV/Hz Digital Input / Output Input HIGH Level VIH Input LOW Level VIL Output HIGH Level VOH IOL=1mA Output LOW Level VOL IOH-1mA 0.7xDVDD V 0.3xDVDD V 0.1xDVDD V 0.9xDVDD V TERMINOLOGY 1. MICN input only in single ended microphone configuration. Maximum input signal to MICP without distortion is -3dBV. 2. Hold Time is the length of time between a signal detected being too quiet and beginning to ramp up the gain. It does not apply to ramping down the gain when the signal is too loud, which happens without a delay. 3. Ramp-up and Ramp-Down times are defined as the time it takes for the PGA to change it's gain by 6dB. 4. All hold, ramp-up and ramp-down times scale proportionally with MCLK 5. Signal-to-noise ratio (dB) - SNR is a measure of the difference in level between the full scale output and the output with no signal applied. (No Auto-zero or Automute function is employed in achieving these results). 6. THD+N (dB) - THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal. w PD Rev 4.2 January 2008 7 WM8950 Production Data SIGNAL TIMING REQUIREMENTS SYSTEM CLOCK TIMING tMCLKL MCLK tMCLKH tMCLKY Figure 1 System Clock Timing Requirements Test Conditions DCVDD=1.8V, DBVDD=AVDD=SPKVDD=3.3V, DGND=AGND=SPKGND=0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT System Clock Timing Information MCLK System clock cycle time TMCLKY Tbd MCLK duty cycle TMCLKDS 60:40 ns 40:60 AUDIO INTERFACE TIMING - MASTER MODE Figure 2 Digital Audio Data Timing - Master Mode (see Control Interface) w PD Rev 4.2 January 2008 8 WM8950 Production Data Test Conditions DCVDD=1.8V, DBVDD=AVDD=SPKVDD=3.3V, DGND=AGND=SPKGND=0V, TA=+25oC, Master Mode, fs=48kHz, MCLK=256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Audio Data Input Timing Information FRAME propagation delay from BCLK falling edge tDL 10 ns ADCDAT propagation delay from BCLK falling edge tDDA 10 ns AUDIO INTERFACE TIMING - SLAVE MODE Figure 3 Digital Audio Data Timing - Slave Mode Test Conditions DCVDD=1.8V, DBVDD=AVDD=SPKVDD=3.3V, DGND=AGND=SPKGND=0V, TA=+25oC, Slave Mode, fs=48kHz, MCLK= 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Audio Data Input Timing Information BCLK cycle time tBCY 50 ns BCLK pulse width high tBCH 20 ns BCLK pulse width low tBCL 20 ns FRAME set-up time to BCLK rising edge tLRSU 10 ns FRAME hold time from BCLK rising edge tLRH 10 ns ADCDAT propagation delay from BCLK falling edge tDD 20 ns Note: BCLK period should always be greater than or equal to MCLK period. w PD Rev 4.2 January 2008 9 WM8950 Production Data CONTROL INTERFACE TIMING - 3-WIRE MODE Figure 4 Control Interface Timing - 3-Wire Serial Control Mode Test Conditions DCVDD = 1.8V, DBVDD = AVDD = SPKVDD = 3.3V, DGND = AGND = SPKGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT Program Register Input Information SCLK rising edge to CSB rising edge tSCS 80 ns SCLK pulse cycle time tSCY 200 ns SCLK pulse width low tSCL 80 ns SCLK pulse width high tSCH 80 ns SDIN to SCLK set-up time tDSU 40 ns SCLK to SDIN hold time tDHO 40 ns CSB pulse width low tCSL 40 ns CSB pulse width high tCSH 40 ns CSB rising to SCLK rising tCSS 40 ns tps 0 Pulse width of spikes that will be suppressed w 5 ns PD Rev 4.2 January 2008 10 WM8950 Production Data CONTROL INTERFACE TIMING - 2-WIRE MODE t3 t3 t5 SDIN t4 t6 t2 t8 SCLK t1 t9 t7 Figure 5 Control Interface Timing - 2-Wire Serial Control Mode Test Conditions DCVDD=1.8V, DBVDD=AVDD=SPKVDD=3.3V, DGND=AGND=SPKGND=0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER SYMBOL MIN TYP MAX UNIT 526 kHz Program Register Input Information SCLK Frequency 0 SCLK Low Pulse-Width t1 1.3 us SCLK High Pulse-Width t2 600 ns Hold Time (Start Condition) t3 600 ns Setup Time (Start Condition) t4 600 ns Data Setup Time t5 100 SDIN, SCLK Rise Time t6 300 SDIN, SCLK Fall Time t7 300 Setup Time (Stop Condition) t8 Data Hold Time t9 Pulse width of spikes that will be suppressed tps w ns 600 0 ns ns ns 900 ns 5 ns PD Rev 4.2 January 2008 11 WM8950 Production Data DEVICE DESCRIPTION INTRODUCTION The WM8950 is a low power audio ADC, with flexible line and microphone input. Applications for this device include games console accessories, digital still cameras, voice recorders and other general purpose audio applications. FEATURES The chip offers great flexibility in use, and so can support many different modes of operation as follows: MICROPHONE INPUTS Microphone inputs are provided, allowing for either a differential microphone input or a single ended microphone to be connected. These inputs have a user programmable gain range of -12dB to +35.25dB using internal resistors. After the input PGA stage comes a boost stage which can add a further 20dB of gain. A microphone bias is output from the chip which can be used to bias the microphones. The signal routing can be configured to allow manual adjustment of mic levels, or to allow the ALC loop to control the level of mic signal that is transmitted. Total gain through the microphone paths of up to +55.25dB can be selected. PGA AND ALC OPERATION A programmable gain amplifier is provided in the input path to the ADC. This may be used manually or in conjunction with a mixed analogue/digital automatic level control (ALC) which keeps the recording volume constant. AUX INPUT The device includes a mono input, AUX, that can be used as an input for warning tones (beep) etc. This path can also be summed into the input in a flexible fashion, either to the input PGA as a second microphone input or as a line input. The configuration of this circuit, with integrated on-chip resistors allows several analogue signals to be summed into the single AUX input if required. ADC The mono ADC uses a multi-bit high-order oversampling architecture to deliver optimum performance with low power consumption. Various sample rates are supported, from the 8ks/s rate typically used in voice dictation, up to the 48ks/s rate used in high quality audio applications. DIGITAL FILTERING Advanced Sigma Delta Converters are used along with digital decimation and interpolation filters to give high quality audio at sample rates from 8ks/s to 48ks/s. Application specific digital filters are also available which help to reduce the effect of specific noise sources such as `wind noise'. The filters include a programmable ADC high pass filter, an IIR filter with fully programmable coefficients, and a 5-band equaliser that can be applied to the record path in order to improve the overall audio sound from the device. AUDIO INTERFACES The WM8950 has a standard audio interface, to support the transmission of audio data from the chip. This interface is a 4 wire standard audio interface which supports a number of audio data formats including I2S, DSP Mode, MSB-First, left justified and MSB-First, right justified, and can operate in master or slave modes. CONTROL INTERFACES To allow full software control over all its features, the WM8950 offers a choice of 2 or 3 wire MPU control interface. It is fully compatible and an ideal partner for a wide range of industry standard microprocessors, controllers and DSPs. The selection between 2-wire mode and 3-wire mode is determined by the state of the MODE pin. If MODE is high then 3-wire control mode is selected, if MODE is low then 2-wire control mode is selected. In 2 wire mode, only slave operation is supported, and the address of the device is fixed as 0011010. w PD Rev 4.2 January 2008 12 WM8950 Production Data CLOCKING SCHEMES WM8950 offers the normal audio clocking scheme operation, where 256fs MCLK is provided to the ADC. However, a PLL is also included which may be used to generate the internal master clock frequency in the event that this is not available from the system controller. This PLL uses an input clock, typically the 12MHz USB or ilink clock, to generate high quality audio clocks. If this PLL is not required for generation of these clocks, it can be reconfigured to generate alternative clocks which may then be output on the CSB/GPIO pin and used elsewhere in the system. POWER CONTROL The design of the WM8950 has given much attention to power consumption without compromising performance. It operates at low supply voltages, and includes the facility to power off any unused parts of the circuitry under software control, includes standby and power off modes. INPUT SIGNAL PATH The WM8950 has 3 flexible analogue inputs: two microphone inputs, and an auxiliary input. These inputs can be used in a variety of ways. The input signal path before the ADC has a flexible PGA block which then feeds into a gain boost/mixer stage. MICROPHONE INPUTS The WM8950 can accommodate a variety of microphone configurations including single ended and differential inputs. The inputs through the MICN, MICP and optionally AUX pins are amplified through the input PGA as shown in Figure 6 . A pseudo differential input is the preferential configuration where the positive terminal of the input PGA is connected to the MICP input pin by setting MICP2INPPGA=1. The microphone ground should then be connected to MICN (when MICN2INPPGA=1) or optionally to AUX (when AUX2INPPGA=1) input pins. Alternatively a single ended microphone can be connected to the MICN input with MICN2INPPGA set to 1. The non-inverting terminal of the input PGA should be connected internally to VMID by setting MICP2INPPGA to 0. Figure 6 Microphone Input PGA Circuit (switch positions shown are for differential mic input) w PD Rev 4.2 January 2008 13 WM8950 Production Data REGISTER ADDRESS R44 Input Control BIT LABEL DEFAULT DESCRIPTION 0 MICP2INPPGA 1 Connect input PGA amplifier positive terminal to MICP or VMID. 0 = input PGA amplifier positive terminal connected to VMID 1 = input PGA amplifier positive terminal connected to MICP through variable resistor string 1 MICN2INPPGA 1 Connect MICN to input PGA negative terminal. 0=MICN not connected to input PGA 1=MICN connected to input PGA amplifier negative terminal. 2 AUX2INPPGA 0 Select AUX amplifier output as input PGA signal source. 0=AUX not connected to input PGA 1=AUX connected to input PGA amplifier negative terminal. The input PGA is enabled by the IPPGAEN register bit. REGISTER ADDRESS BIT 2 R2 Power Management 2 LABEL DEFAULT INPPGAEN 0 DESCRIPTION Input microphone PGA enable 0 = disabled 1 = enabled INPUT PGA VOLUME CONTROL The input microphone PGA has a gain range from -12dB to +35.25dB in 0.75dB steps. The gain from the MICN input to the PGA output and from the AUX amplifier to the PGA output are always common and controlled by the register bits INPPGAVOL[5:0]. These register bits also affect the MICP pin when MICP2INPPGA=1. When the Automatic Level Control (ALC) is enabled the input PGA gain is then controlled automatically and the INPPGAVOL bits should not be used. REGISTER ADDRESS R45 Input PGA volume control BIT LABEL DEFAULT DESCRIPTION 5:0 INPPGAVOL 010000 Input PGA volume 000000 = -12dB 000001 = -11.25db . 010000 = 0dB . 111111 = 35.25dB 6 INPPGAMUTE 0 Mute control for input PGA: 0=Input PGA not muted, normal operation 1=Input PGA muted (and disconnected from the following input BOOST stage). 7 INPPGAZC 0 Input PGA zero cross enable: 0=Update gain when gain register changes 1=Update gain on 1st zero cross after gain register write. ALCSEL 0 ALC function select: 0=ALC off (PGA gain set by INPPGAVOL register bits) 1=ALC on (ALC controls PGA gain) R32 8 ALC control 1 Table 1 Input PGA Volume Control w PD Rev 4.2 January 2008 14 WM8950 Production Data AUXILIARY INPUT An auxiliary input circuit (Figure 7) is provided which consists of an amplifier which can be configured either as an inverting buffer for a single input signal or as a mixer/summer for multiple inputs with the use of external resistors. The circuit is enabled by the register bit AUXEN. Figure 7 Auxiliary Input Circuit The AUXMODE register bit controls the auxiliary input mode of operation: In buffer mode (AUXMODE=0) the switch labelled AUXSW in Figure 7 is open and the signal at the AUX pin will be buffered and inverted through the aux circuit using only the internal components. In mixer mode (AUXMODE=1) the on-chip input resistor is bypassed, this allows the user to sum in multiple inputs with the use of external resistors. When used in this mode there will be gain variations through this path from part to part due to the variation of the internal 20k resistors relative to the higher tolerance external resistors. REGISTER ADDRESS BIT LABEL DEFAULT DESCRIPTION R1 Power management 1 6 AUXEN 0 Auxiliary input buffer enable 0 = OFF 1 = ON R44 Input control 3 AUXMODE 0 0 = inverting buffer 1 = mixer (on-chip input resistor bypassed) Table 2 Auxiliary Input Buffer Control INPUT BOOST The input BOOST circuit has 3 selectable inputs: the input microphone PGA output, the AUX amplifier output and the MICP input pin (when not using a differential microphone configuration). These three inputs can be mixed together and have individual gain boost/adjust as shown in Figure 8. w PD Rev 4.2 January 2008 15 WM8950 Production Data Figure 8 Input Boost Stage The input PGA path can have a +20dB boost (PGABOOST=1) a 0dB pass through (PGABOOST=0) or be completely isolated from the input boost circuit (INPPGAMUTE=1). REGISTER ADDRESS BIT R45 6 Input PGA gain control R47 Input BOOST control 8 LABEL DEFAULT DESCRIPTION INPPGAMUTE 0 Mute control for input PGA: 0=Input PGA not muted, normal operation 1=Input PGA muted (and disconnected from the following input BOOST stage). PGABOOST 1 0 = PGA output has +0dB gain through input BOOST stage. 1 = PGA output has +20dB gain through input BOOST stage. Table 3 Input BOOST Stage Control The Auxiliary amplifier path to the BOOST stage is controlled by the AUX2BOOSTVOL[2:0] register bits. When AUX2BOOSTVOL=000 this path is completely disconnected from the BOOST stage. Settings 001 through to 111 control the gain in 3dB steps from -12dB to +6dB. The MICP path to the BOOST stage is controlled by the MICP2BOOSTVOL[2:0] register bits. When MICP2BOOSTVOL=000 this input pin is completely disconnected from the BOOST stage. Settings 001 through to 111 control the gain in 3dB steps from -12dB to +6dB. REGISTER ADDRESS R47 Input BOOST control BIT LABEL DEFAULT DESCRIPTION 2:0 AUX2BOOSTVOL 000 Controls the auxiliary amplifer to the input boost stage: 000=Path disabled (disconnected) 001=-12dB gain through boost stage 010=-9dB gain through boost stage ... 111=+6dB gain through boost stage 6:4 MICP2BOOSTVOL 000 Controls the MICP pin to the input boost stage (NB, when using this path set MICPZIUNPPGA=0): 000=Path disabled (disconnected) 001=-12dB gain through boost stage 010=-9dB gain through boost stage ... 111=+6dB gain through boost stage Table 4 Input BOOST Stage Control w PD Rev 4.2 January 2008 16 WM8950 Production Data The BOOST stage is enabled under control of the BOOSTEN register bit. REGISTER ADDRESS R2 Power management 2 BIT 4 LABEL DEFAULT BOOSTEN 0 DESCRIPTION Input BOOST enable 0 = Boost stage OFF 1 = Boost stage ON Table 5 Input BOOST Enable Control MICROPHONE BIASING CIRCUIT The MICBIAS output provides a low noise reference voltage suitable for biasing electret type microphones and the associated external resistor biasing network. Refer to the Applications Information section for recommended external components. The MICBIAS voltage can be altered via the MBVSEL register bit. When MBVSEL=0, MICBIAS=0.9*AVDD and when MBVSEL=1, MICBIAS=0.65*AVDD. The output can be enabled or disabled using the MICBEN control bit. REGISTER ADDRESS R1 Power management 1 BIT 4 LABEL DEFAULT MICBEN 0 DESCRIPTION Microphone Bias Enable 0 = OFF (high impedance output) 1 = ON Table 6 Microphone Bias Enable REGISTER ADDRESS R44 Input Control BIT 8 LABEL DEFAULT MBVSEL 0 DESCRIPTION Microphone Bias Voltage Control 0 = 0.9 * AVDD 1 = 0.65 * AVDD Table 7 Microphone Bias Voltage Control The internal MICBIAS circuitry is shown in Figure 9. Note that the maximum source current capability for MICBIAS is 3mA. The external biasing resistors therefore must be large enough to limit the MICBIAS current to 3mA. VMID MB internal resistor internal resistor MBVSEL=0 MICBIAS = 1.8 x VMID = 0.9 X AVDD MBVSEL=1 MICBIAS = 1.3 x VMID = 0.65 X AVDD AGND Figure 9 Microphone Bias Schematic w PD Rev 4.2 January 2008 17 WM8950 Production Data ANALOGUE TO DIGITAL CONVERTER (ADC) The WM8950 uses a multi-bit, oversampled sigma-delta ADC channel. The use of multi-bit feedback and high oversampling rates reduces the effects of jitter and high frequency noise. The ADC Full Scale input level is proportional to AVDD. With a 3.3V supply voltage, the full scale level is 1.0Vrms. Any voltage greater than -1dBfs may overload the ADC and cause distortion. ADC DIGITAL FILTERS The ADC filters perform true 24 bit signal processing to convert the raw multi-bit oversampled data from the ADC to the correct sampling frequency to be output on the digital audio interface. The digital filter path is illustrated in Figure 10 . Figure 10 ADC Digital Filter Path The ADC is enabled by the ADCEN register bit. REGISTER ADDRESS R2 Power management 2 BIT 0 LABEL ADCEN DEFAULT 0 DESCRIPTION 0 = ADC disabled 1 = ADC enabled Table 8 ADC Enable The polarity of the output signal can also be changed under software control using the ADCPOL register bit. The oversampling rate of the ADC can be adjusted using the ADCOSR register bit. With ADCOSR=0 the oversample rate is 64x which gives lowest power operation and when ADCOSR=1 the oversample rate is 128x which gives best performance. REGISTER ADDRESS R14 ADC Control BIT LABEL DEFAULT DESCRIPTION 3 ADCOSR 0 ADC oversample rate select: 0=64x (lower power) 1=128x (best performance) 0 ADCPOL 0 0=normal 1=inverted Table 9 ADC Oversample Rate Select w PD Rev 4.2 January 2008 18 WM8950 Production Data SELECTABLE HIGH PASS FILTER A selectable high pass filter is provided. To disable this filter set HPFEN=0. The filter has two modes controlled by HPFAPP. In Audio Mode (HPFAPP=0) the filter is first order, with a cut-off frequency of 3.7Hz. In Application Mode (HPFAPP=1) the filter is second order, with a cut-off frequency selectable via the HPFCUT register. The cut-off frequencies when HPFAPP=1 are shown in Table 11. REGISTER ADDRESS BIT R14 ADC Control LABEL DEFAULT 8 HPFEN 1 7 HPFAPP 0 6:4 HPFCUT 000 DESCRIPTION High Pass Filter Enable 0=disabled 1=enabled Select audio mode or application mode 0=Audio mode (1st order, fc = ~3.7Hz) 1=Application mode (2nd order, fc = HPFCUT) Application mode cut-off frequency See Table 11 for details. Table 10 ADC Filter Select SAMPLE FREQUENCY (kHz) HPFCUT [2:0] 8 000 82 001 010 11.025 12 16 24 32 113 122 82 113 122 82 113 122 102 141 153 131 180 156 102 141 153 102 141 153 131 180 156 131 180 011 163 225 156 245 163 225 245 163 225 100 204 245 281 306 204 281 306 204 281 101 306 261 360 392 261 360 392 261 360 392 110 327 450 490 327 450 490 327 450 490 111 408 563 612 408 563 612 408 563 612 SR=101/100 22.05 SR=011/010 44.1 48 SR=001/000 Table 11 High Pass Filter Cut-off Frequencies (HPFAPP=1) Values in Hz Note that the High Pass filter values (when HPFAPP=1) work on the basis that the SR register bits are set correctly for the actual sample rate as shown in Table 11. w PD Rev 4.2 January 2008 19 WM8950 Production Data PROGRAMMABLE IIR FILTER An IIR filter with fully programmable coefficients is provided, typically used as a notch filter for removing narrow band noise at a given frequency. This notch filter has a variable centre frequency and bandwidth, programmable via two coefficients, a0 and a1. These coefficients should be converted to 2's complement numbers to determine the register values. a0 and a1 are represented by the register bits NFA0[13:0] and NFA1[13:0]. Because these coefficient values require four register writes to setup there is an NFU (Notch Filter Update) flag which should be set only when all four registers are setup. REGISTER ADDRESS R27 Notch Filter 1 BIT LABEL DEFAULT DESCRIPTION 6:0 NFA0[13:7] 0 Notch Filter a0 coefficient, bits [13:7] 7 NFEN 0 Notch filter enable: 0=Disabled 1=Enabled 8 NFU 0 Notch filter update. The notch filter values used internally only update when one of the NFU bits is set high. R28 Notch Filter 2 6:0 NFA0[6:0] 0 Notch Filter a0 coefficient, bits [6:0] 8 NFU] 0 Notch filter update. The notch filter values used internally only update when one of the NFU bits is set high. R29 Notch Filter 3 6:0 NFA1[13:7] 0 Notch Filter a1 coefficient, bits [13:7] 8 NFU 0 Notch filter update. The notch filter values used internally only update when one of the NFU bits is set high. R30 Notch Filter 4 6:0 NFA1[6:0] 0 Notch Filter a1 coefficient, bits [6:0] 8 NFU 0 Notch filter update. The notch filter values used internally only update when one of the NFU bits is set high. Table 12 Notch Filter Function The coefficients are calculated as follows: a0 = 1 - tan( wb / 2) 1 + tan( wb / 2) a1 = -(1 + a0 ) cos(w0 ) Where: w0 = 2f c / f s wb = 2f b / f s fc = centre frequency in Hz, fb = -3dB bandwidth in Hz, fs = sample frequency in Hz The coefficients are calculated as follows: NFA0 = -a0 x 213 NFA1 = -a1 x 212 These values are then converted to 2's complement notation to determine the register values. NOTCH FILTER WORKED EXAMPLE The following example illustrates how to calculate the a0 and a1 coefficients for a desired centre frequency and -3dB bandwidth. w PD Rev 4.2 January 2008 20 WM8950 Production Data fc = 1000 Hz fb = 100 Hz fs = 48000 Hz w 0 = 2fc / fs = 2 x (1000 / 48000) = 0.1308996939 rads w b = 2fb / fs = 2 x (100 / 48000) = 0.01308996939 rads a0 = 1 - tan( w b / 2) 1 + tan( w b / 2) = 1 - tan(0.0130899693 9 / 2) 1 + tan( 0.0130899693 9 / 2) a1 = -(1 + a0 ) cos( w 0 ) = 0.9869949627 = -(1 + 0.9869949627 ) cos(0.1308996939 ) = -1.969995945 NFn_A0 = -a0 x 213 = -8085 (rounded to nearest whole number) NFn_A1 = -a1 x 212 = 8069 (rounded to nearest whole number) These values are then converted to 2's complement: NFA0 = 14'h206B = 14'b10000001101011 NFA1 = 14'h1F85 = 14'b 01111110000101 DIGITAL ADC VOLUME CONTROL The output of the ADCs can be digitally attenuated over a range from -127dB to 0dB in 0.5dB steps. The gain for a given eight-bit code X is given by: Gain = 0.5 x (x-255) dB for 1 x 255, MUTE for x = 0 REGISTER ADDRESS R15 ADC Digital Volume BIT 7:0 LABEL ADCVOL [7:0] DEFAULT 11111111 ( 0dB ) DESCRIPTION ADC Digital Volume Control 0000 0000 = Digital Mute 0000 0001 = -127dB 0000 0010 = -126.5dB ... 0.5dB steps up to 1111 1111 = 0dB Table 13 ADC Volume INPUT AUTOMATIC LEVEL CONTROL (ALC) The WM8950 has an automatic PGA gain control circuit, which can function as an input peak limiter or as an automatic level control (ALC). The Automatic Level Control (ALC) provides continuous adjustment of the input PGA in response to the amplitude of the input signal. A digital peak detector monitors the input signal amplitude and compares it to a register defined threshold level (ALCLVL). If the signal is below the threshold, the ALC will increase the gain of the PGA at a rate set by ALCDCY. If the signal is above the threshold, the ALC will reduce the gain of the PGA at a rate set by ALCATK. The ALC has two modes selected by the ALCMODE register: normal mode and peak limiter mode. The ALC/limiter function is enabled by setting the register bit R32[8] ALCSEL. w PD Rev 4.2 January 2008 21 WM8950 Production Data REGISTER ADDRESS BIT R32 (20h) 2:0 ALC Control 1 DEFAULT DESCRIPTION ALCMIN [2:0] 000 (-12dB) Set minimum gain of PGA 000 = -12dB 001 = -6dB 010 = 0dB 011 = +6dB 100 = +12dB 101 = +18dB 110 = +24dB 111 = +30dB 5:3 ALCMAX [2:0] 111 (+35.25dB) Set Maximum Gain of PGA 111 = +35.25dB 110 = +29.25dB 101 = +23.25dB 100 = +17.25dB 011 = +11.25dB 010 = +5.25dB 001 = -0.75dB 000 = -6.75dB 8 ALCSEL 0 ALC function select 0 = ALC disabled 1 = ALC enabled ALCLVL [3:0] 1011 (-12dB) ALC target - sets signal level at ADC input 1111 = -6dBFS 1110 = -7.5dBFS 1101 = -9dBFS 1100 = -10.5dBFS 1011 = -12dBFS 1010 = -13.5dBFS 1001 = -15dBFS 1000 = -16.5dBFS 0111 = -18dBFS 0110 = -19.5dBFS 0101 = -21dBFS 0100 = -22.5dBFS 0011 = -24dBFS 0010 = -25.5dBFS 0001 = -27dBFS 0000 = -28.5dBFS 8 ALCZC 0 (zero cross off) ALC uses zero cross detection circuit. 0 = Disabled (recommended) 1 = Enabled 7:4 ALCHLD [3:0] 0000 (0ms) ALC hold time before gain is increased. 0000 = 0ms 0001 = 2.67ms 0010 = 5.33ms 0011 = 10.66ms 0100 = 21.32ms 0101 = 42.64ms 0110 = 85.28ms 0111 = 0.17s 1000 = 0.34s 1001 = 0.68s 1010 or higher = 1.36s R33 (21h) 3:0 ALC Control 2 w LABEL PD Rev 4.2 January 2008 22 WM8950 Production Data REGISTER ADDRESS BIT R34 (22h) 8 ALC Control 3 7:4 LABEL DEFAULT ALCMODE 0 ALCDCY [3:0] 0011 (26ms/6dB) DESCRIPTION Determines the ALC mode of operation: 0 = ALC mode (Normal Operation) 1 = Limiter mode. Decay (gain ramp-up) time (ALCMODE ==0) Per step Per 6dB 90% of range 0000 410us 3.38ms 23.6ms 0001 820us 6.56ms 47.2ms 0010 1.64ms 13.1ms 94.5ms ... (time doubles with every step) 420ms 3.36s 24.2s 1010 or higher 0011 (5.8ms/6dB) Decay (gain ramp-up) time (ALCMODE ==1) Per step Per 6dB 90% of range 0000 90.8us 726us 5.23ms 0001 182us 1.45ms 10.5ms 0010 363us 2.91ms 20.9ms ... (time doubles with every step) 1010 93ms 744ms 5.36s 3:0 ALCATK [3:0] 0010 (3.3ms/6dB) ALC attack (gain ramp-down) time (ALCMODE == 0) Per step Per 6dB 90% of range 0000 104us 832us 0001 208us 1.66ms 6ms 12ms 0010 416us 3.33ms 24ms ... (time doubles with every step) 1010 or 106ms 852ms 6.13s higher 0010 (726us/6dB) ALC attack (gain ramp-down) time (ALCMODE == 1) Per step Per 6dB 90% of range 0000 22.7us 182.4us 1.31ms 0001 45.4us 363us 2.62ms 0010 90.8us 726us 5.23ms ... (time doubles with every step) 1010 or 23.2ms 186ms 1.34s higher Table 14 ALC Control Registers When the ALC is disabled, the input PGA remains at the last controlled value of the ALC. An input gain update must be made by writing to the INPPGAVOLL/R register bits. NORMAL MODE In normal mode, the ALC will attempt to maintain a constant signal level by increasing or decreasing the gain of the PGA. The following diagram shows an example of this. w PD Rev 4.2 January 2008 23 WM8950 Production Data Figure 11 ALC Normal Mode Operation w PD Rev 4.2 January 2008 24 WM8950 Production Data LIMITER MODE In limiter mode, the ALC will reduce peaks that go above the threshold level, but will not increase the PGA gain beyond the starting level. The starting level is the PGA gain setting when the ALC is enabled in limiter mode. If the ALC is started in limiter mode, this is the gain setting of the PGA at start-up. If the ALC is switched into limiter mode after running in ALC mode, the starting gain will be the gain at switchover. The diagram below shows an example of limiter mode. Figure 12 ALC Limiter Mode Operation ATTACK AND DECAY TIMES The attack and decay times set the update times for the PGA gain. The attack time is the time constant used when the gain is reducing. The decay time is the time constant used when the gain is increasing. In limiter mode, the time constants are faster than in ALC mode. The time constants are shown below in terms of a single gain step, a change of 6dB and a change of 90% of the PGAs gain range. Note that, these times will vary slightly depending on the sample rate used (specified by the SR register). w PD Rev 4.2 January 2008 25 WM8950 Production Data NORMAL MODE ALCMODE = 0 (Normal Mode) ALCATK 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 tATK 104s 208s 416s 832s 1.66ms 3.33ms 6.66ms 13.3ms 26.6ms 53.2ms 106ms Attack Time (s) tATK6dB tATK90% 832s 6ms 1.66ms 12ms 3.33ms 24ms 6.66ms 48ms 13.3ms 96ms 26.6ms 192ms 53.2ms 384ms 106ms 767ms 213.2ms 1.53s 426ms 3.07s 852ms 6.13s ALCMODE = 0 (Normal Mode) ALCDCY 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 tDCY 410s 820s 1.64ms 3.28ms 6.56ms 13.1ms 26.2ms 52.5ms 105ms 210ms 420ms Decay Time (s) tDCY6dB tDCY90% 3.28ms 23.6ms 6.56ms 47.2ms 13.1ms 94.5ms 26.2ms 189ms 52.5ms 378ms 105ms 756ms 210ms 1.51s 420ms 3.02s 840ms 6.05s 1.68s 12.1s 3.36s 24.2s Table 15 ALC Normal Mode (Attack and Decay times) w PD Rev 4.2 January 2008 26 WM8950 Production Data LIMITER MODE ALCMODE = 1 (Limiter Mode) ALCATK 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 tATKLIM 22.7s 45.4S 90.8S 182S 363S 726S 1.45ms 2.9ms 5.81ms 11.6ms 23.2ms Attack Time (s) tATKLIM6dB tATKLIM90% 182s 1.31ms 363s 2.62ms 726s 5.23ms 1.45ms 10.5ms 2.91ms 20.9ms 5.81ms 41.8ms 11.6ms 83.7ms 23.2ms 167ms 46.5ms 335ms 93ms 669ms 186ms 1.34s ALCMODE = 1 (Limiter Mode) ALCDCY 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 tDCYLIM 90.8s 182S 363S 726S 1.45ms 2.91ms 5.81ms 11.6ms 23.2ms 46.5ms 93ms Attack Time (s) tDCYLIM6dB tDCYLIM90% 726s 5.23ms 1.45ms 10.5ms 2.91ms 20.9ms 5.81ms 41.8ms 11.6ms 83.7ms 23.2ms 167ms 46.5ms 335ms 93ms 669ms 186ms 1.34s 372ms 2.68s 744ms 5.36s Table 16 ALC Limiter Mode (Attack and Decay times) w PD Rev 4.2 January 2008 27 WM8950 Production Data MINIMUM AND MAXIMUM GAIN The ALCMIN and ALCMAX register bits set the minimum/maximum gain value that the PGA can be set to whilst under the control of the ALC. This has no effect on the PGA when ALC is not enabled. REGISTER ADDRESS BIT R32 5:3 ALC Control 1 2:0 LABEL DEFAULT DESCRIPTION ALCMAX 111 Set Maximum Gain of PGA ALCMIN 000 Set minimum gain of PGA Table 17 ALC Max/Min Gain In normal mode, ALCMAX sets the maximum boost which can be applied to the signal. In limiter mode, ALCMAX will normally have no effect (assuming the starting gain value is less than the maximum gain specified by ALCMAX) because the maximum gain is set at the starting gain level. ALCMIN sets the minimum gain value which can be applied to the signal. Figure 13 ALC Min/Max Gain ALCMAX 111 110 101 100 011 010 001 000 Maximum Gain (dB) 35.25 29.25 23.25 17.25 11.25 5.25 -0.75 -6.75 Table 18 ALC Max Gain Values w PD Rev 4.2 January 2008 28 WM8950 Production Data ALCMIN 000 001 010 011 100 101 110 111 Minimum Gain (dB) -12 -6 0 6 12 18 24 30 Table 19 ALC Min Gain Values Note that if the ALC gain setting strays outside the ALC operating range, either by starting the ALC outside of the range or changing the ALCMAX or ALCMIN settings during operation, the ALC will immediately adjust the gain to return to the ALC operating range. It is recommended that the ALC starting gain is set between the ALCMAX and ALCMIN limits. ALC HOLD TIME (NORMAL MODE ONLY) In Normal mode, the ALC has an adjustable hold time which sets a time delay before the ALC begins its decay phase (gain increasing). The hold time is set by the ALCHLD register. REGISTER ADDRESS BIT 7:4 R33 ALC Control 2 LABEL ALCHLD DEFAULT 0000 DESCRIPTION ALC hold time before gain is increased. Table 20 ALC Hold Time If the hold time is exceeded this indicates that the signal has reached a new average level and the ALC will increase the gain to adjust for that new average level. If the signal goes above the threshold during the hold period, the hold phase is abandoned and the ALC returns to normal operation. w PD Rev 4.2 January 2008 29 WM8950 Production Data Figure 14 ALCLVL w PD Rev 4.2 January 2008 30 WM8950 Production Data Figure 15 ALC Hold Time ALCHLD 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 tHOLD (s) 0 2.67ms 5.34ms 10.7ms 21.4ms 42.7ms 85.4ms 171ms 342ms 684ms 1.37s Table 21 ALC Hold Time Values w PD Rev 4.2 January 2008 31 WM8950 Production Data PEAK LIMITER To prevent clipping when a large signal occurs just after a period of quiet, the ALC circuit includes a limiter function. If the ADC input signal exceeds 87.5% of full scale (-1.16dB), the PGA gain is ramped down at the maximum attack rate (as when ALCATK = 0000), until the signal level falls below 87.5% of full scale. This function is automatically enabled whenever the ALC is enabled. Note: If ALCATK = 0000, then the limiter makes no difference to the operation of the ALC. It is designed to prevent clipping when long attack times are used. NOISE GATE (NORMAL MODE ONLY) When the signal is very quiet and consists mainly of noise, the ALC function may cause "noise pumping", i.e. loud hissing noise during silence periods. The WM8950 has a noise gate function that prevents noise pumping by comparing the signal level at the input pins against a noise gate threshold, NGTH. The noise gate cuts in when: Signal level at ADC [dBFS] < NGTH [dBFS] + PGA gain [dB] + Mic Boost gain [dB] This is equivalent to: Signal level at input pin [dBFS] < NGTH [dBFS] The PGA gain is then held constant (preventing it from ramping up as it normally would when the signal is quiet). The table below summarises the noise gate control register. The NGTH control bits set the noise gate threshold with respect to the ADC full-scale range. The threshold is adjusted in 6dB steps. Levels at the extremes of the range may cause inappropriate operation, so care should be taken with set-up of the function. The noise gate only operates in conjunction with the ALC and cannot be used in limiter mode. REGISTER ADDRESS R35 (23h) ALC Noise Gate Control BIT 2:0 3 LABEL DEFAULT DESCRIPTION NGTH 000 Noise gate threshold: 000 = -39dB 001 = -45dB 010 = -51db 011 = -57dB 100 = -63dB 101 = -69dB 110 = -75dB 111 = -81dB NGATEN 0 Noise gate function enable 1 = enable 0 = disable Table 22 ALC Noise Gate Control The diagrams below show the response of the system to the same signal with and without noise gate. w PD Rev 4.2 January 2008 32 Production Data WM8950 Figure 16 ALC Operation Above Noise Gate Threshold w PD Rev 4.2 January 2008 33 WM8950 Production Data Figure 17 Noise Gate Operation GRAPHIC EQUALISER A 5-band graphic EQ is provided, which can be applied to the ADC data under control of the EQMODE register bit. REGISTER ADDRESS R18 EQ Control 1 BIT 8 LABEL EQMODE DEFAULT 1 DESCRIPTION 0 = Equaliser applied to ADC data 1 = Equaliser bypassed Table 23 EQ Select w PD Rev 4.2 January 2008 34 WM8950 Production Data The equaliser consists of low and high frequency shelving filters (Band 1 and 5) and three peak filters for the centre bands. Each has adjustable cut-off or centre frequency, and selectable boost (+/- 12dB in 1dB steps). The peak filters have selectable bandwidth. REGISTER ADDRESS R18 EQ Band 1 Control BIT LABEL DEFAULT 4:0 EQ1G 01100 (0dB) 6:5 EQ1C 01 DESCRIPTION Band 1 Gain Control. See Table 29 for details. Band 1 Cut-off Frequency: 00=80Hz 01=105Hz 10=135Hz 11=175Hz Table 24 EQ Band 1 Control REGISTER ADDRESS R19 EQ Band 2 Control BIT LABEL DEFAULT DESCRIPTION 4:0 EQ2G 01100 (0dB) Band 2 Gain Control. See Table 29 for details. 6:5 EQ2C 01 Band 2 Centre Frequency: 8 EQ2BW 00=230Hz 01=300Hz 10=385Hz 11=500Hz Band 2 Bandwidth Control 0=narrow bandwidth 1=wide bandwidth 0 Table 25 EQ Band 2 Control REGISTER ADDRESS R20 EQ Band 3 Control BIT LABEL DEFAULT 4:0 EQ3G 01100 (0dB) 6:5 EQ3C 01 8 EQ3BW 0 DESCRIPTION Band 3 Gain Control. See Table 29 for details. Band 3 Centre Frequency: 00=650Hz 01=850Hz 10=1.1kHz 11=1.4kHz Band 3 Bandwidth Control 0=narrow bandwidth 1=wide bandwidth Table 26 EQ Band 3 Control w PD Rev 4.2 January 2008 35 WM8950 Production Data REGISTER ADDRESS R21 EQ Band 4 Control BIT LABEL DEFAULT DESCRIPTION 4:0 EQ4G 01100 (0dB) Band 4 Gain Control. See Table 29 for details 6:5 EQ4C 01 Band 4 Centre Frequency: 8 EQ4BW 00=1.8kHz 01=2.4kHz 10=3.2kHz 11=4.1kHz Band 4 Bandwidth Control 0=narrow bandwidth 1=wide bandwidth 0 Table 27 EQ Band 4 Control REGISTER ADDRESS R22 EQ Band 5 Gain Control BIT LABEL DEFAULT 4:0 EQ5G 01100 (0dB) 6:5 EQ5C 01 DESCRIPTION Band 5 Gain Control. See Table 29 for details. Band 5 Cut-off Frequency: 00=5.3kHz 01=6.9kHz 10=9kHz 11=11.7kHz Table 28 EQ Band 5 Control GAIN REGISTER GAIN 00000 +12dB 00001 +11dB 00010 +10dB .... (1dB steps) 01100 0dB 01101 -1dB 11000 to 11111 -12dB Table 29 Gain Register Table w PD Rev 4.2 January 2008 36 WM8950 Production Data A dedicated buffer is available for tieing off unused analogue input pins as shown below Figure 18. This buffer can be enabled using the BUFIOEN register bit. Figure 18 Unused Input Pin Tie-off Buffers THERMAL SHUTDOWN To protect the WM8950 from overheating a thermal shutdown circuit is included. If the device temperature reaches approximately 1250C and the thermal shutdown circuit is enabled (TSDEN=1), an interrupt can be generated. See the GPIO and Interrupt Controller section for details. REGISTER ADDRESS R49 Output control BIT 1 LABEL TSDEN DEFAULT 1 DESCRIPTION Thermal Shutdown Enable 0 : thermal shutdown disabled 1 : thermal shutdown enabled Table 30 Thermal Shutdown w PD Rev 4.2 January 2008 37 WM8950 Production Data DIGITAL AUDIO INTERFACES The audio interface has three pins: * * * ADCDAT: ADC data output FRAME: Data alignment clock BCLK: Bit clock, for synchronisation The clock signals BCLK, and FRAME can be outputs when the WM8950 operates as a master, or inputs when it is a slave (see Master and Slave Mode Operation, below). Five different audio data formats are supported: * * * * Left justified Right justified I 2S DSP mode All of these modes are MSB first. They are described in Audio Data Formats, below. Refer to the Electrical Characteristic section for timing information. MASTER AND SLAVE MODE OPERATION The WM8950 audio interface may be configured as either master or slave. As a master interface device the WM8950 generates BCLK and FRAME and thus controls sequencing of the data transfer on ADCDAT. To set the device to master mode register bit MS should be set high. In slave mode (MS=0), the WM8950 responds with data to clocks it receives over the digital audio interfaces. AUDIO DATA FORMATS In Left Justified mode, the MSB is available on the first rising edge of BCLK following an FRAME transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles before each FRAME transition. Figure 19 Left Justified Audio Interface (assuming n-bit word length) In Right Justified mode, the LSB is available on the last rising edge of BCLK before a FRAME transition. All other bits are transmitted before (MSB first). Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles after each FRAME transition. w PD Rev 4.2 January 2008 38 WM8950 Production Data Figure 20 Right Justified Audio Interface (assuming n-bit word length) In I2S mode, the MSB is available on the second rising edge of BCLK following a FRAME transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of one sample and the MSB of the next. Figure 21 I2S Audio Interface (assuming n-bit word length) In DSP/PCM mode, the left channel MSB is available on the 2nd (mode A) rising edge of BCLK following a rising edge of FRAME. Right channel data immediately follows left channel data. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of the right channel data and the next sample. In device master mode, the LRC output will resemble the frame pulse shown in Figure 22. In device slave mode, Figure 23 it is possible to use any length of frame pulse less than 1/fs, providing the falling edge of the frame pulse occurs greater than one BCLK period before the rising edge of the next frame pulse. Figure 22 DSP/PCM Mode Audio Interface (mode A, LRP=0, Master) w PD Rev 4.2 January 2008 39 WM8950 Production Data Figure 23 DSP/PCM Mode Audio Interface (mode A, LRP=0, Slave) When using ADCLRSWAP = 1 in DSP/PCM mode, the data will appear in the Right Phase of the FRAME, which will be 16/20/24/32 bits after the FRAME pulse. REGISTER ADDRESS R4 Audio interface control BIT LABEL DEFAULT DESCRIPTION 1 ADCLRSWAP 0 Controls whether ADC data appears in `right' or `left' phases of FRAME clock: 0=ADC data appear in `left' phase of FRAME 1=ADC data appears in `right' phase of FRAME 4:3 FMT 10 Audio interface Data Format Select: 00=Right Justified 01=Left Justified 10=I2S format 11= DSP/PCM mode 6:5 WL 10 Word length 00=16 bits 01=20 bits 10=24 bits 11=32 bits (see note) 7 FRAMEP 0 Frame clock polarity 0=normal 1=inverted 8 BCP 0 BCLK polarity 0=normal 1=inverted DSP Mode - reserved Table 31 Audio Interface Control w PD Rev 4.2 January 2008 40 WM8950 Production Data AUDIO INTERFACE CONTROL The register bits controlling audio format, word length and master / slave mode are summarised below. Each audio interface can be controlled individually. Register bit MS selects audio interface operation in master or slave mode. In Master mode BCLK, and FRAME are outputs. The frequency of BCLK and FRAME in master mode are controlled with BCLKDIV. These are divided down versions of master clock. This may result in short BCLK pulses at the end of a frame if there is a non-integer ratio of BCLKs to FRAME clocks. REGISTER ADDRESS R6 Clock generation control BIT LABEL DEFAULT DESCRIPTION 0 MS 0 Sets the chip to be master over FRAME and BCLK 0=BCLK and FRAME clock are inputs 1=BCLK and FRAME clock are outputs generated by the WM8950 (MASTER) 4:2 BCLKDIV 000 Configures the BCLK and FRAME output frequency, for use when the chip is master over BCLK. 000=divide by 1 (BCLK=MCLK) 001=divide by 2 (BCLK=MCLK/2) 010=divide by 4 011=divide by 8 100=divide by 16 101=divide by 32 110=reserved 111=reserved 7:5 MCLKDIV 010 Sets the scaling for either the MCLK or PLL clock output (under control of CLKSEL) 000=divide by 1 001=divide by 1.5 010=divide by 2 011=divide by 3 100=divide by 4 101=divide by 6 110=divide by 8 111=divide by 12 8 CLKSEL 1 Controls the source of the clock for all internal operation: 0=MCLK 1=PLL output Table 32 Clock Control COMPANDING The WM8950 supports A-law and -law companding. Companding can be enabled on the ADC audio interface by writing the appropriate value to the ADC_COMP register bit. w PD Rev 4.2 January 2008 41 WM8950 Production Data REGISTER ADDRESS BIT R5 Companding control 2:1 LABEL DEFAULT ADC_COMP 0 DESCRIPTION ADC companding 00=off 01=reserved 10=-law 11=A-law Table 33 Companding Control Companding involves using a piecewise linear approximation of the following equations (as set out by ITU-T G.711 standard) for data compression: -law (where =255 for the U.S. and Japan): F(x) = ln( 1 + |x|) / ln( 1 + ) -1 x 1 A-law (where A=87.6 for Europe): F(x) = A|x| / ( 1 + lnA) } for x 1/A F(x) = ( 1 + lnA|x|) / (1 + lnA) } for 1/A x 1 The companded data is also inverted as recommended by the G.711 standard (all 8 bits are inverted for -law, all even data bits are inverted for A-law). The data will be transmitted as the first 8 MSB's of data. Companding converts 13 bits (-law) or 12 bits (A-law) to 8 bits using non-linear quantization. The input data range is separated into 8 levels, allowing low amplitude signals better precision than that of high amplitude signals. This is to exploit the operation of the human auditory system, where louder sounds do not require as much resolution as quieter sounds. The companded signal is an 8bit word containing sign (1-bit), exponent (3-bits) and mantissa (4-bits). BIT7 BIT[6:4] BIT[3:0] SIGN EXPONENT MANTISSA Table 34 8-bit Companded Word Composition u-law Companding 1 120 0.9 Companded Output 0.7 80 0.6 0.5 60 0.4 40 0.3 Normalised Output 0.8 100 0.2 20 0.1 0 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Normalised Input Figure 24 u-Law Companding w PD Rev 4.2 January 2008 42 WM8950 Production Data A-law Companding 1 120 0.9 Companded Output 0.7 80 0.6 0.5 60 0.4 40 0.3 Normalised Output 0.8 100 0.2 20 0.1 0 0 0 0.2 0.4 0.6 0.8 1 Normalised Input Figure 25 A-Law Companding AUDIO SAMPLE RATES The WM8950 sample rate for the ADC is set using the SR register bits. The cutoffs for the digital filters and the ALC attack/decay times stated are determined using these values and assume a 256fs master clock rate. If a sample rate that is not explicitly supported by the SR register settings is required then the closest SR value to that sample rate should be chosen, the filter characteristics and the ALC attack, decay and hold times will scale appropriately. REGISTER ADDRESS R7 Additional control BIT 3:1 LABEL SR DEFAULT 000 DESCRIPTION Approximate sample rate (configures the coefficients for the internal digital filters): 000=48kHz 001=32kHz 010=24kHz 011=16kHz 100=12kHz 101=8kHz 110-111=reserved Table 35 Sample Rate Control MASTER CLOCK AND PHASE LOCKED LOOP (PLL) The WM8950 has an on-chip phase-locked loop (PLL) circuit that can be used to: Generate master clocks for the WM8950 audio functions from another external clock, e.g. in telecoms applications. Generate and output (on pin CSB/GPIO) a clock for another part of the system that is derived from an existing audio master clock. Figure 26 shows the PLL and internal clocking arrangement on the WM8950. The PLL can be enabled or disabled by the PLLEN register bit. w PD Rev 4.2 January 2008 43 WM8950 Production Data REGISTER ADDRESS BIT R1 Power management 1 LABEL 5 PLLEN DEFAULT 0 DESCRIPTION PLL enable 0=PLL off 1=PLL on Table 36 PLLEN Control Bit Figure 26 PLL and Clock Select Circuit The PLL frequency ratio R = f2/f1 (see Figure 26) can be set using the register bits PLLK and PLLN: PLLN = int R 24 PLLK = int (2 (R-PLLN)) EXAMPLE: MCLK=12MHz, required clock = 12.288MHz. R should be chosen to ensure 5 < PLLN < 13. There is a fixed divide by 4 in the PLL and a selectable divide by N after the PLL which should be set to divide by 2 to meet this requirement. Enabling the divide by 2 sets the required f2 = 4 x 2 x 12.288MHz = 98.304MHz. R = 98.304 / 12 = 8.192 PLLN = int R = 8 k = int ( 224 x (8.192 - 8)) = 3221225 = 3126E9h REGISTER ADDRESS R36 PLL N value BIT LABEL DEFAULT DESCRIPTION 4 PLLPRESCALE 0 0 = MCLK input not divided (default) 1 = Divide MCLK by 2 before input to PLL 3:0 PLLN 1000 Integer (N) part of PLL input/output frequency ratio. Use values greater than 5 and less than 13. R37 PLL K value 1 5:0 PLLK [23:18] 0Ch R38 PLL K Value 2 8:0 PLLK [17:9] 093h Fractional (K) part of PLL1 input/output frequency ratio (treat as one 24-digit binary number). R39 PLL K Value 3 8:0 PLLK [8:0] 0E9h Table 37 PLL Frequency Ratio Control w PD Rev 4.2 January 2008 44 WM8950 Production Data The PLL performs best when f2 is around 90MHz. Its stability peaks at N=8. Some example settings are shown in Figure 35. MCLK (MHz) (F1) DESIRED OUTPUT (MHz) PRESCALE POSTSCALE DIVIDE DIVIDE F2 (MHz) R N (Hex) K (Hex) 86C220 12 11.2896 90.3168 1 2 7.5264 7 12 12.288 98.304 1 2 8.192 8 3126E8 13 11.2896 90.3168 1 2 6.947446 6 F28BD4 13 12.288 98.304 1 2 7.561846 7 8FD525 14.4 11.2896 90.3168 1 2 6.272 6 45A1CA D3A06E 14.4 12.288 98.304 1 2 6.826667 6 19.2 11.2896 90.3168 2 2 9.408 9 6872AF 19.2 12.288 98.304 2 2 10.24 A 3D70A3 19.68 11.2896 90.3168 2 2 9.178537 9 2DB492 19.68 12.288 98.304 2 2 9.990243 9 FD809F 19.8 11.2896 90.3168 2 2 9.122909 9 1F76F7 19.8 12.288 98.304 2 2 9.929697 9 EE009E 24 11.2896 90.3168 2 2 7.5264 7 86C226 24 12.288 98.304 2 2 8.192 8 3126E8 26 11.2896 90.3168 2 2 6.947446 6 F28BD4 26 12.288 98.304 2 2 7.561846 7 8FD525 27 11.2896 90.3168 2 2 6.690133 6 BOAC93 27 12.288 98.304 2 2 7.281778 7 482296 Table 38 PLL Frequency Examples GENERAL PURPOSE INPUT/OUTPUT The CSB/GPIO pin can be configured to perform a variety of useful tasks by setting the GPIOSEL register bits. The GPIO is only available in 2 wire mode. REGISTER ADDRESS R8 GPIO control BIT LABEL DEFAULT DESCRIPTION 2:0 GPIOSEL 000 CSB/GPIO pin function select: 000=CSB input 001=Reserved 010=Temp ok 011=Amute active 100=PLL clk o/p 101=PLL lock 110=Reserved 111=Reserved 3 GPIOPOL 0 GPIO Polarity invert 0=Non inverted 1=Inverted 5:4 OPCLKDIV 00 PLL Output clock division ratio 00=divide by 1 01=divide by 2 10=divide by 3 11=divide by 4 Table 39 CSB/GPIO Control w PD Rev 4.2 January 2008 45 WM8950 Production Data CONTROL INTERFACE SELECTION OF CONTROL MODE AND 2-WIRE MODE ADDRESS The control interface can operate as either a 3-wire or 2-wire MPU interface. The MODE pin determines the 2 or 3 wire mode as shown in Table 40. The WM8950 is controlled by writing to registers through a serial control interface. A control word consists of 16 bits. The first 7 bits (B15 to B9) are address bits that select which control register is accessed. The remaining 9 bits (B8 to B0) are register bits, corresponding to the 9 bits in each control register. MODE INTERFACE FORMAT Low 2 wire High 3 wire Table 40 Control Interface Mode Selection 3-WIRE SERIAL CONTROL MODE In 3-wire mode, every rising edge of SCLK clocks in one data bit from the SDIN pin. A rising edge on CSB/GPIO latches in a complete control word consisting of the last 16 bits. Figure 27 3-Wire Serial Control Interface 2-WIRE SERIAL CONTROL MODE The WM8950 supports software control via a 2-wire serial bus. Many devices can be controlled by the same bus, and each device has a unique 7-bit device address (this is not the same as the 7-bit address of each register in the WM8950). The WM8950 operates as a slave device only. The controller indicates the start of data transfer with a high to low transition on SDIN while SCLK remains high. This indicates that a device address and data will follow. All devices on the 2-wire bus respond to the start condition and shift in the next eight bits on SDIN (7-bit address + Read/Write bit, MSB first). If the device address received matches the address of the WM8950, then the WM8950 responds by pulling SDIN low on the next clock pulse (ACK). If the address is not recognised or the R/W bit is `1' when operating in write only mode, the WM8950 returns to the idle condition and wait for a new start condition and valid address. During a write, once the WM8950 has acknowledged a correct address, the controller sends the first byte of control data (B15 to B8, i.e. the WM8950 register address plus the first bit of register data). The WM8950 then acknowledges the first data byte by pulling SDIN low for one clock pulse. The controller then sends the second byte of control data (B7 to B0, i.e. the remaining 8 bits of register data), and the WM8950 acknowledges again by pulling SDIN low. Transfers are complete when there is a low to high transition on SDIN while SCLK is high. After a complete sequence the WM8950 returns to the idle state and waits for another start condition. If a start or stop condition is detected out of sequence at any point during data transfer (i.e. SDIN changes while SCLK is high), the device jumps to the idle condition. w PD Rev 4.2 January 2008 46 WM8950 Production Data DEVICE ADDRESS (7 BITS) SDIN RD / WR BIT ACK (LOW) CONTROL BYTE 1 (BITS 15 TO 8) ACK (LOW) CONTROL BYTE 1 (BITS 7 TO 0) ACK (LOW) SCLK START register address and 1st register data bit remaining 8 bits of register data STOP Figure 28 2-Wire Serial Control Interface In 2-wire mode the WM8950 has a fixed device address, 0011010. RESETTING THE CHIP The WM8950 can be reset by performing a write of any value to the software reset register (address 0 hex). This will cause all register values to be reset to their default values. In addition to this there is a Power-On Reset (POR) circuit which ensures that the registers are set to default when the device is powered up. POWER SUPPLIES The WM8950 can use up to three separate power supplies: AVDD, AVDD2, AGND and AGND2: Analogue supply, powers all analogue functions. AVDD can range from 2.5V to 3.6V and has the most significant impact on overall power consumption. A large AVDD slightly improves audio quality. DCVDD: Digital core supply, powers all digital functions except the audio and control interfaces. DCVDD can range from 1.71V to 3.6V, and has no effect on audio quality. The return path for DCVDD is DGND, which is shared with DBVDD. DBVDD Can range from 1.71V to 3.6V. DBVDD return path is through DGND. It is possible to use the same supply voltage for all supplies. However, digital and analogue supplies should be routed and decoupled separately on the PCB to keep digital switching noise out of the analogue signal paths. w PD Rev 4.2 January 2008 47 WM8950 Production Data ADC POWER UP/DOWN SEQUENCE Vpor_on Vpora Vpor_off Power Supply DGND POR Device Ready No Power POR Undefined Internal POR active POR DNC I2S Clocks DNC tadcint ADC Internal State Power down Init tadcint Normal Operation PD Init Normal Operation tmidrail_on tmidrail_off (Note 1) Analogue Inputs Power down (Note 2) AVDD/2 GD GD GD GD ADCDAT pin (Note 3) ADCEN bit ADC enabled ADC off INPPGAEN bit VMIDSEL/ BIASEN bits ADC enabled INPPGA enabled (Note 4) VMID enabled Figure 29 ADC Power Up and Down Sequence (not to scale) SYMBOL MIN TYPICAL MAX UNIT tmidrail_on 500 tmidrail_off >10 ms s tadcint 2/fs n/fs Table 41 Typical POR Operation (typical values, not tested) Notes: w 1. The analogue input pin charge time, tmidrail_on, is determined by the VMID pin charge time. This time is dependent upon the value of VMID decoupling capacitor and VMID pin input resistance and AVDD power supply rise time. 2. The analogue input pin discharge time, tmidrail_off, is determined by the analogue input coupling capacitor discharge time. The time, tmidrail_off, is measured using a 1F capacitor on the analogue input but will vary dependent upon the value of input coupling capacitor. 3. While the ADC is enabled there will be LSB data bit activity on the ADCDAT pin due to system noise but no significant digital output will be present. 4. The VMIDSEL and BIASEN bits must be set to enable analogue input midrail voltage and for normal ADC operation. 5. ADCDAT data output delay from power up - with power supplies starting from 0V - is determined primarily by the VMID charge time. ADC initialisation and power management bits may be set immediately after POR is released; VMID charge time will be significantly longer and will dictate when the device is stabilised for analogue input. 6. ADCDAT data output delay at power up from device standby (power supplies already applied) is determined by ADC initialisation time, 2/fs. PD Rev 4.2 January 2008 48 WM8950 Production Data POWER MANAGEMENT SAVING POWER BY REDUCING OVERSAMPLING RATE The default mode of operation of the ADC digital filters is in 64x oversampling mode. Under the control of ADCOSR the oversampling rate may be doubled. 64x oversampling results in a slight decrease in noise performance compared to 128x but lowers the power consumption of the device. REGISTER ADDRESS R14 ADC control BIT LABEL 3 ADCOSR128 DEFAULT 0 DESCRIPTION ADC oversample rate select 0 = 64x (lowest power) 1 = 128x (best SNR) Table 42 ADC Oversampling Rate Selection VMID The analogue circuitry will not work unless VMID is enabled (VMIDSEL00). The impedance of the VMID resistor string, together with the decoupling capacitor on the VMID pin will determine the startup time of the VMID circuit. REGISTER ADDRESS R1 Power management 1 BIT 1:0 LABEL DEFAULT VMIDSEL 00 DESCRIPTION Reference string impedance to VMID pin (detemines startup time): 00=off (open circuit) 01=50k 10=500k 11=5k (for fastest startup) Table 43 VMID Impedance Control BIASEN REGISTER ADDRESS R1 Power management 1 BIT 3 LABEL BIASEN DEFAULT 0 DESCRIPTION Analogue amplifier bias control Table 44 BIASEN Control ESTIMATED SUPPLY CURRENTS When the ADC is enabled it is estimated that approximately 4mA will be drawn from DCVDD when DCVDD=1.8V and fs=48kHz (This will be lower at lower sample rates). When the PLL is enabled an additional 700 microamps will be drawn from DCVDD. Table 59 shows the estimated 3.3V AVDD current drawn by various circuits, by register bit. REGISTER BIT AVDD CURRENT (MILLIAMPS) PLLEN 1.4 (with clocks applied) MICBEN 0.5 BIASEN 0.3 BUFIOEN 0.1 VMIDSEL 10K=>0.3, less than 0.1 for 50k/500k INPPGAEN 0.2 ADCEN x64 (ADCOSR=0)=>2.6, x128 (ADCOSR=1)=>4.9 Table 45 AVDD Supply Current w PD Rev 4.2 January 2008 49 WM8950 Production Data REGISTER MAP ADDR B[15:9] REGISTER NAME B8 B7 B6 B5 B4 B3 B2 B1 B0 DEF'T VAL (HEX) DEC HEX 0 00 Software Reset 1 01 Power manage't 1 0 0 AUXEN PLLEN MICBEN BIASEN BUFIOEN 2 02 Power manage't 2 0 0 0 0 BOOSTEN 0 INPPGAEN 0 ADCEN 000 4 04 Audio Interface BCP FRAMEP 0 ALRSWAP 0 050 5 05 Companding ctrl 0 0 0 000 6 06 Clock Gen ctrl CLKSEL MS 140 7 07 Additional ctrl 0 SLOWCLK EN 000 8 08 GPIO Stuff 14 0E ADC Control 15 0F ADC Digital Vol 0 18 12 EQ1 - low shelf 0 0 EQ1C EQ1G 12C 19 13 EQ2 - peak 1 EQ2BW 0 EQ2C EQ2G 02C 20 14 EQ3 - peak 2 EQ3BW 0 EQ3C EQ3G 02C 21 15 EQ4 - peak 3 EQ4BW 0 EQ4C EQ4G 02C 22 16 EQ5 - high shelf 0 0 EQ5C EQ5G 02C 27 1B Notch Filter 1 NFU NFEN NFA0[13:7] 000 28 1C Notch Filter 2 NFU 0 NFA0[6:0] 000 29 1D Notch Filter 3 NFU 0 NFA1[13:7] 000 30 1E Notch Filter 4 NFU 0 NFA1[6:0] 32 20 ALC control 1 ALCSEL 0 33 21 ALC control 2 ALCZC 34 22 ALC control 3 ALCMODE 35 23 Noise Gate 0 0 0 0 0 36 24 PLL N 0 0 0 0 PLL_PRE SCALE 37 25 PLL K 1 0 0 0 38 26 PLL K 2 PLLK[17:9] 093 39 27 PLL K 3 PLLK[8:0] 0E9 44 2C Input ctrl 45 2D INP PGA gain ctrl 47 2F ADC Boost ctrl 49 31 Thermal Shutdown w Software reset WL FMT 0 0 0 MCLKDIV 0 0 0 0 0 HPFEN HPFAPP ADC_COMP BCLKDIV 0 0 0 SR OPCLKDIV GPIOPOL HPFCUT ADCOSR 128 000 VMIDSEL 000 GPIOSEL 0 0 ADCPOL 0FF ADCVOL 0 000 ALCMAX ALCDCY ALCLVL 00B ALCATK 032 NGEN 000 NGTH 008 PLLN[3:0] 00C PLLK[23:18] 0 0 0 INPPGAZC INPPGA MUTE PGABOOST 0 0 0 0 0 AUXMODE AUX2 INPPGA MICN2 INPPGA MICP2 INPPGA 0 0 0 0 100 AUX2BOOSTVOL 0 003 010 INPPGAVOL MICP2BOOSTVOL 0 038 ALCMIN ALCHLD MBVSEL 100 TSDEN 0 002 PD Rev 4.2 January 2008 50 WM8950 Production Data DIGITAL FILTER CHARACTERISTICS PARAMETER TEST CONDITIONS MIN TYP MAX UNIT ADC Filter Passband +/- 0.025dB 0 -6dB 0.454fs 0.5fs Passband Ripple +/- 0.025 Stopband Stopband Attenuation dB 0.546fs f > 0.546fs -60 Group Delay dB 21/fs ADC High Pass Filter High Pass Filter Corner Frequency -3dB 3.7 -0.5dB 10.4 -0.1dB 21.6 Hz Table 46 Digital Filter Characteristics TERMINOLOGY 1. Stop Band Attenuation (dB) - the degree to which the frequency spectrum is attenuated (outside audio band) 2. Pass-band Ripple - any variation of the frequency response in the pass-band region 3. Note that this delay applies only to the filters and does not include additional delays through other digital circuits. See Table 47 for the total delay. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT ADC Path Group Delay Total Delay (ADC analogue input to digital audio interface output) EQ disabled 26/fs 28/fs 30/fs EQ enabled 27/fs 29/fs 31/fs Table 47 Total Group Delay Notes 1. Wind noise filter is disabled. w PD Rev 4.2 January 2008 51 WM8950 Production Data ADC FILTER RESPONSES 0.2 0 0.15 0.1 Response (dB) Response (dB) -20 -40 -60 -80 0.05 0 -0.05 -0.1 -100 -0.15 -0.2 -120 0 0.5 1 1.5 2 Frequency (Fs) Figure 30 ADC Digital Filter Frequency Response w 2.5 3 0 0.1 0.2 0.3 0.4 0.5 Frequency (Fs) Figure 31 ADC Digital Filter Ripple PD Rev 4.2 January 2008 52 WM8950 Production Data DE-EMPHASIS FILTER RESPONSES 0 0.30 -1 0.25 -2 0.20 Response (dB) Response (dB) -3 -4 -5 -6 -7 0.15 0.10 0.05 0.00 -8 -0.05 -9 -0.10 -10 -0.15 0 2000 4000 6000 8000 10000 12000 14000 16000 0 2000 4000 Frequency (Hz) Figure 32 De-emphasis Frequency Response (32kHz) 8000 10000 12000 14000 16000 Figure 33 De-emphasis Error (32kHz) 0.10 0 -1 0.05 -2 Response (dB) -3 Response (dB) 6000 Frequency (Hz) -4 -5 -6 -7 -8 0.00 -0.05 -0.10 -0.15 -9 -10 -0.20 0 5000 10000 15000 20000 0 5000 Frequency (Hz) Figure 34 De-emphasis Frequency Response (44.1kHz) 15000 20000 Figure 35 De-emphasis Error (44.1kHz) 0 0.10 -1 0.08 -2 0.06 -3 0.04 Response (dB) Response (dB) 10000 Frequency (Hz) -4 -5 -6 -7 0.02 0.00 -0.02 -0.04 -8 -0.06 -9 -0.08 -10 -0.10 0 5000 10000 15000 20000 Frequency (Hz) Figure 36 De-emphasis Frequency Response (48kHz) w 0 5000 10000 15000 20000 Frequency (Hz) Figure 37 De-emphasis Error (48kHz) PD Rev 4.2 January 2008 53 WM8950 Production Data HIGHPASS FILTER The WM8950 has a selectable digital highpass filter in the ADC filter path. This filter has two modes, audio and applications. In audio mode the filter is a 1st order IIR with a cut-off of around 3.7Hz. In applications mode the filter is a 2nd order high pass filter with a selectable cut-off frequency. 5 10 0 0 -5 -10 -15 Response (dB) Response (dB) -10 -20 -25 -30 -35 -20 -30 -40 -40 0 5 10 15 20 25 30 35 40 45 -50 Frequency (Hz) -60 0 200 400 600 800 1000 1200 Frequency (Hz) Figure 38 ADC Highpass Filter Response, HPFAPP=0 Figure 39 ADC Highpass Filter Responses (48kHz), HPFAPP=1, all cut-off settings shown. 10 10 0 0 -10 -10 -20 Response (dB) Response (dB) -20 -30 -40 -30 -40 -50 -60 -50 -70 -60 -80 -70 -90 0 -80 200 400 600 800 1000 1200 Frequency (Hz) 0 200 400 600 800 1000 1200 Frequency (Hz) Figure 40 ADC Highpass Filter Responses (24kHz), HPFAPP=1, all cut-off settings shown. w Figure 41 ADC Highpass Filter Responses (12kHz), HPFAPP=1, all cut-off settings shown. PD Rev 4.2 January 2008 54 WM8950 Production Data 5-BAND EQUALISER 15 15 10 10 5 5 Magnitude (dB) Magnitude (dB) The WM8950 has a 5-band equaliser which can be applied to the ADC path. The plots from Figure 42 to Figure 55 show the frequency responses of each filter with a sampling frequency of 48kHz, firstly showing the different cut-off/centre frequencies with a gain of 12dB, and secondly a sweep of the gain from -12dB to +12dB for the lowest cut-off/centre frequency of each filter. 0 0 -5 -5 -10 -10 -15 -1 10 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 -15 -1 10 5 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 15 15 10 10 5 5 Magnitude (dB) Magnitude (dB) Figure 42 EQ Band 1 - Low Frequency Shelf Filter Cut-offs Figure 43 EQ Band 1 - Gains for Lowest Cut-off Frequency 0 0 -5 -5 -10 -10 -15 -1 10 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 Figure 44 EQ Band 2 - Peak Filter Centre Frequencies, EQ2BW=0 -15 -1 10 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 Figure 45 EQ Band 2 - Peak Filter Gains for Lowest Cut-off Frequency, EQ2BW=0 15 10 Magnitude (dB) 5 0 -5 -10 -15 -2 10 10 -1 10 0 1 10 Frequency (Hz) 10 2 10 3 10 4 Figure 46 EQ Band 2 - EQ2BW=0, EQ2BW=1 w PD Rev 4.2 January 2008 55 Production Data 15 15 10 10 5 5 Magnitude (dB) Magnitude (dB) WM8950 0 0 -5 -5 -10 -10 -15 -1 10 10 0 1 10 2 10 Frequency (Hz) 10 3 10 4 10 5 Figure 47 EQ Band 3 - Peak Filter Centre Frequencies, EQ3BW=0 -15 -1 10 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 Figure 48 EQ Band 3 - Peak Filter Gains for Lowest Cut-off Frequency, EQ3BW=0 15 10 Magnitude (dB) 5 0 -5 -10 -15 -2 10 Figure 49 10 -1 0 10 1 10 Frequency (Hz) 10 2 10 3 10 4 EQ Band 3 - EQ3BW=0, EQ3BW=1 w PD Rev 4.2 January 2008 56 WM8950 15 15 10 10 5 5 Magnitude (dB) Magnitude (dB) Production Data 0 0 -5 -5 -10 -10 -15 -1 10 10 0 1 10 2 10 Frequency (Hz) 10 3 10 4 10 -15 -1 10 5 Figure 50 EQ Band 4 - Peak Filter Centre Frequencies, EQ3BW=0 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 Figure 51 EQ Band 4 - Peak Filter Gains for Lowest Cut-off Frequency, EQ4BW=0 15 10 Magnitude (dB) 5 0 -5 -10 -15 -2 10 -1 0 10 1 10 Frequency (Hz) 10 2 10 3 10 4 EQ Band 4 - EQ3BW=0, EQ3BW=1 15 15 10 10 5 5 Magnitude (dB) Magnitude (dB) Figure 52 10 0 0 -5 -5 -10 -10 -15 -1 10 Figure 53 10 0 1 10 2 10 Frequency (Hz) 10 3 10 4 10 5 -15 -1 10 EQ Band 5 - High Frequency Shelf Filter Cut-offsFigure 54 w 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 EQ Band 5 - Gains for Lowest Cut-off Frequency PD Rev 4.2 January 2008 57 WM8950 Production Data Figure 55 shows the result of having the gain set on more than one channel simultaneously. The blue traces show each band (lowest cut-off/centre frequency) with 12dB gain. The red traces show the cumulative effect of all bands with +12dB gain and all bands -12dB gain, with EQxBW=0 for the peak filters. 20 15 Magnitude (dB) 10 5 0 -5 -10 -15 -1 10 Figure 55 w 10 0 10 1 2 10 Frequency (Hz) 10 3 10 4 10 5 Cumulative Frequency Boost/Cut PD Rev 4.2 January 2008 58 Production Data WM8950 APPLICATIONS INFORMATION RECOMMENDED EXTERNAL COMPONENTS Figure 56 Recommended External Components w PD Rev 4.2 January 2008 59 WM8950 Production Data PACKAGE DIAGRAM FL: 24 PIN QFN PLASTIC PACKAGE 4 X 4 X 0.9 mm BODY, 0.50 mm LEAD PITCH DM045.B DETAIL 1 D D2 19 24 1 18 EXPOSED GROUND 6 PADDLE A INDEX AREA (D/2 X E/2) 4 E2 E SEE DETAIL 2 13 6 12 7 2X b e 1 bbb M C A B 2X aaa C aaa C TOP VIEW BOTTOM VIEW DETAIL 1 A 0.08 C 45 degrees A1 SIDE VIEW C DETAIL 2 Datum L1 0.32mm DETAIL 2 SEATING PLANE L 5 1 ccc C A3 EXPOSED GROUND PADDLE W Terminal Tip e/2 e R T A3 G H b Exposed lead Half etch tie bar DETAIL 2 Symbols A A1 A3 b D D2 E E2 e G H L L1 T MIN 0.80 0 0.18 2.55 2.55 0.30 0.03 Dimensions (mm) NOM MAX NOTE 0.90 1.00 0.02 0.05 0.20 REF 1 0.25 0.30 4.00 BSC 2.70 4.00 BSC 2.70 0.50 BSC 0.213 0.1 0.40 2.80 2 2.80 2 0.50 0.15 7 0.1 0.2 W Tolerances of Form and Position aaa bbb ccc REF: 0.15 0.10 0.10 JEDEC, MO-220, VARIATION VGGD-2. NOTES: 1. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.15 mm AND 0.30 mm FROM TERMINAL TIP. 2. FALLS WITHIN JEDEC, MO-220, VARIATION VGGD-2. 3. ALL DIMENSIONS ARE IN MILLIMETRES. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JEDEC 95-1 SPP-002. 5. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 6. REFER TO APPLICATIONS NOTE WAN_0118 FOR FURTHER INFORMATION REGARDING PCB FOOTPRINTS AND QFN PACKAGE SOLDERING. 7. DEPENDING ON THE METHOD OF LEAD TERMINATION AT THE EDGE OF THE PACKAGE, PULL BACK (L1) MAY BE PRESENT. 8. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE. w PD Rev 4.2 January 2008 60 Production Data WM8950 IMPORTANT NOTICE Wolfson Microelectronics plc ("Wolfson") products and services are sold subject to Wolfson's terms and conditions of sale, delivery and payment supplied at the time of order acknowledgement. Wolfson warrants performance of its products to the specifications in effect at the date of shipment. Wolfson reserves the right to make changes to its products and specifications or to discontinue any product or service without notice. Customers should therefore obtain the latest version of relevant information from Wolfson to verify that the information is current. Testing and other quality control techniques are utilised to the extent Wolfson deems necessary to support its warranty. Specific testing of all parameters of each device is not necessarily performed unless required by law or regulation. In order to minimise risks associated with customer applications, the customer must use adequate design and operating safeguards to minimise inherent or procedural hazards. Wolfson is not liable for applications assistance or customer product design. The customer is solely responsible for its selection and use of Wolfson products. Wolfson is not liable for such selection or use nor for use of any circuitry other than circuitry entirely embodied in a Wolfson product. Wolfson's products are not intended for use in life support systems, appliances, nuclear systems or systems where malfunction can reasonably be expected to result in personal injury, death or severe property or environmental damage. Any use of products by the customer for such purposes is at the customer's own risk. Wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other intellectual property right of Wolfson covering or relating to any combination, machine, or process in which its products or services might be or are used. Any provision or publication of any third party's products or services does not constitute Wolfson's approval, licence, warranty or endorsement thereof. Any third party trade marks contained in this document belong to the respective third party owner. Reproduction of information from Wolfson datasheets is permissible only if reproduction is without alteration and is accompanied by all associated copyright, proprietary and other notices (including this notice) and conditions. Wolfson is not liable for any unauthorised alteration of such information or for any reliance placed thereon. Any representations made, warranties given, and/or liabilities accepted by any person which differ from those contained in this datasheet or in Wolfson's standard terms and conditions of sale, delivery and payment are made, given and/or accepted at that person's own risk. Wolfson is not liable for any such representations, warranties or liabilities or for any reliance placed thereon by any person. ADDRESS Wolfson Microelectronics plc Westfield House 26 Westfield Road Edinburgh EH11 2QB United Kingdom Tel :: +44 (0)131 272 7000 Fax :: +44 (0)131 272 7001 Email :: sales@wolfsonmicro.com w PD Rev 4.2 January 2008 61