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WM8722 Stereo DAC with Integrated Tone Generator and Line/Variable Level Outputs
Advanced Information, May 2000, Rev 1.5
DESCRIPTION
The WM8722 is a high performance stereo DAC designed for audio applications such as digital TV and set top boxes. The WM8722 has two stereo analogue outputs, one at line level and one that includes a digitally controllable mute and attenuator function. An on-board tone generator can be routed through the line or variable outputs. WM8722 supports data input word lengths from 16-24 bits and sampling rates up to 96kHz. The WM8722 consists of a serial interface port, digital interpolation filter, multi-bit sigma delta modulator and stereo DAC in a small 20-pin SSOP package. The 3 or 2-wire serial MPU compatible control port provides access to all features including tone generation, on-chip mute, attenuation and phase reversal. The programmable data input port supports glueless interfaces to popular DSPs, audio decoders and S/PDIF and AES/EBU receivers.
FEATURES
* Performance - 102dB SNR (`A' weighted @48kHz) - THD+N: -90dB @ F.S. - 5V or 3V supply operation - Sampling frequency: 8kHz - 96kHz 3-wire or 2-wire serial MPU compatible interface for - Input data word; 16/20/24-Bit - Soft mute - De-emphasis - Volume control On-board tone generator (1Hz - 32kHz, 0.1 - 25.5s) Stereo analogue inputs 20-pin SSOP package
*
* * *
APPLICATIONS
* * * Digital TV Digital broadcast receivers Set top boxes
BLOCK DIAGRAM
MXINL(14)
+12 to -34.5dB, 1.5dB Steps
4
MONO ATTENUATION CONTROL
+
DIN (17) BCKIN (19) LRCIN (18) SCKI (20) I2S/SDIF 16,18, 20 OR 24 BITS
DIGITAL ATTENUATOR AND FILTERS
0/-6dB
(13)LINEOUTL
MULTI BIT
MULTI BIT SC DAC
+
0/-6dB
(12) VAROUTL
L Mix Switches (0-9) R Mix Switches (0-9)
+6 to -73dB, 1dB Steps
MD (3) MC (2) LATCH (4) BUSY (5) SERIAL INPUT INTERFACE
DIGITAL ATTENUATOR AND FILTERS
+
MULTI BIT MULTI BIT SC DAC
0/-6dB
(9) VAROUTR
+
0/-6dB
(8) LINEOUTR
TCLK (1)
TONE GENERATOR
TONE DAC
0 TO -46.5dB, 1.5dB STEPS
WM8722
+12 TO -34.5dB, 1.5dB STEPS
(16) (6) DVDD DGND
(10) AGND
(15) CAP
(11) (7) AVDD MXINR
WOLFSON MICROELECTRONICS LTD
Lutton Court, Bernard Terrace, Edinburgh, EH8 9NX, UK Tel: +44 (0) 131 667 9386 Fax: +44 (0) 131 667 5176 Email: sales@wolfson.co.uk http://www.wolfson.co.uk
Advanced Information data sheets contain preliminary data on new products in the preproduction phase of development. Supplementary data will be published at a later date.
2000 Wolfson Microelectronics Ltd.
WM8722 PIN CONFIGURATION ORDERING INFORMATION
DEVICE TCLK MC MD LATCH BUSY DGND MXINR LINEOUTR VAROUTR AGND 1 2 3 4 5 6 7 8 9 10 20 19 18 17 16 15 14 13 12 11 SCKI BCKIN LRCIN DIN DVDD CAP MXINL LINEOUTL VAROUTL AVDD XWM8722EDS TEMP. RANGE -25 to +85oC
Advanced Information
PACKAGE 20-pin SSOP
PIN DESCRIPTION
PIN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Note: 1. NAME TCLK MC MD LATCH BUSY DGND MXINR VAROUTR LINEOUTR AGND AVDD LINEOUTL VAROUTL MXINL CAP DVDD DIN LRCIN BCKIN SCKI TYPE Digital input Digital input Digital input Digital input Digital I/O Supply Analogue input Analogue output Analogue output Supply Supply Analogue output Analogue output Analogue input Analogue output Supply Digital input Digital input Digital input Digital input DESCRIPTION Tone generator master-clock input. Serial control data clock input (SPI mode) or 2-wire clock input (2-wire mode) Serial control data input (SPI mode) or 2-wire data input (2-wire mode) Latch enable (SPI mode) or address select (2-wire mode). Interface format input pin (0= SPI; 1 = 2-WIRE) or BUSY flag output. Digital ground supply. Analogue mixer input (right channel). Right channel mixer output (variable level). Right channel mixer output (line level). Analogue ground supply. Analogue positive supply. Left channel mixer output (line level). Left channel mixer output (variable level). Analogue mixer input (left channel). Analogue internal reference. Digital positive supply. Serial audio data input. Sample rate clock input. Audio data bit clock input. System clock input (256 or 384fs).
Digital input pins have Schmitt trigger input buffers.
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Advanced Information
WM8722
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.
CONDITION Digital supply voltage Analogue supply voltage Voltage range digital inputs Voltage range analogue inputs Operating temperature range, TA Storage temperature Package body temperature (soldering 10 seconds) Package body temperature (soldering 2 seconds)
MIN -0.3V -0.3V DGND -0.3V AGND -0.3V 0C -65C
MAX +7V +7V DVDD +0.3V AVDD +0.3V +70C +150C +240C +183C
RECOMMENDED OPERATING CONDITIONS
PARAMETER Digital supply range Analogue supply range Ground Difference DGND to AGND Analogue supply current Digital supply current Analogue supply current Digital supply current AVDD = 5V DVDD = 5V AVDD = 3.3V DVDD = 3.3V SYMBOL DVDD AVDD AGND, DGND -0.3 TEST CONDITIONS MIN -10% -10% TYP 3.3 to 5 3.3 to 5 0 0 35 15 tba tba +0.3 MAX +10% +10% UNIT V V V V mA mA mA mA
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WM8722 ELECTRICAL CHARACTERISTICS
Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER DAC Circuit Specifications SNR (Note 1 and 2) AVDD, DVDD = 5V, fs = 48kHz AVDD, DVDD = 3.3V, fs = 48kHz AVDD, DVDD = 5V, fs = 96kHz THD (Note 2) Dynamic range (Note 2) Passband Stopband Passband ripple Stopband Attenuation Channel Separation Gain mismatch channel-to-channel Digital Logic Levels Input LOW level Input HIGH level Output LOW level Output HIGH level Analogue Output Levels Output level Into 10kohm, full scale 0dB, (5V supply) Into 10kohm, full scale 0dB, (3.3V supply) Minimum resistance load To midrail or AC coupled (5V supply) To midrail or AC coupled (3.3V supply) Maximum capacitance load Output DC level Reference Levels Potential divider resistance Voltage at CAP POR POR threshold Analogue Mixer Specifications SNR THD Dynamic Range Channel Separation Output voltage Output current source Output current sink Input voltage, MIXINL/R MIXINL/R input resistance MIXINL/R input resistance WOLFSON MICROELECTRONICS LTD AC coupled 0dB (at 12dB trim) 50 20 Into 10kohm 2 1.5 3 2 1V rms output, Into 10kohm, 50pF load 92 100 -96 100 100 1.2 1.6 AVDD to CAP and CAP to AGND 90 AVDD/2 5V or 3.3V 1.1 0.66 1 600 100 AVDD/2 VIL VIH VOL VOH IOL = 2mA IOH = 2mA AVDD - 0.3V 2.0 f > 0.55fs 0dB -60dB 0.25dB -3dB 0.4535fs 0.491fs 0.25 100 1 100 -95 102 92 102 SYMBOL TEST CONDITIONS MIN TYP
Advanced Information
MAX
UNIT dB dB
-80 dB dB dB dB dB 5 %FSR
0.8 AVSS + 0.3V
V V
Vrms Vrms kohms ohms pF V kohms
2.0
V dB
-92
dB dB dB
1.5
Vrms mA mA
2
Vrms kohm kohm
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Advanced Information Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER Gain mismatch Frequency Bandwidth Master volume max gain Master volume min gain Master volume step size, codes 0 - 47 Master volume step size, codes 48 - 79 Master volume gain code 80 - 127 (mute) Mixer trim max gain Mixer trim min gain Mixer trim step size Tone Generator SINAD (Note 3) SINAD SINAD SINAD Full scale output voltage; trims at Tone Frequency Tone Duration Gain adjust range Gain adjust step size (4 bit trim) 1Hz to 1kHz tones 1kHz to 2kHz tones 2kHz to 4kHz tones 4kHz to 32kHz tones 0dB TCLK frequency = 27MHz TCLK frequency = 27MHz 1 0.1 -46.5 1.25 1.5 65 60 55 50 75 70 65 60 2.5 32767 25.5 0 1.75 SYMBOL TEST CONDITIONS Channel to channel 0dB gain 5 -70 0.7 0.5 -90 11 -32.5 1.3 MIN TYP +/-1% 100 6 -73 1 1 -100 12 -34.5 1.5 13 -36.5 1.7 7 -76 1.3 1.5 MAX +/-5%
WM8722
UNIT % of FSR kHz dB dB dB dB dB dB dB dB dB dB dB dB V pk-pk Hz secs dB dB
Notes: 1. Ratio of output level with 1kHz full scale input, to the output level with all zeros into the digital input, measured `A' weighted over a 20Hz to 20kHz bandwidth. 2. All performance measurements done with 20kHz low pass filter. Failure to use such a filter will result in higher THD+N and lower SNR and Dynamic Range readings than are found in the Electrical Characteristics. The low pass filter removes out of band noise; although it is not audible it may affect dynamic specification values. 3. SINAD is ratio of signal to sum of noise, harmonics and spurii, over a bandwidth from 1Hz up to either 127x the tone frequency, or 20kHz, whichever is the lower. (This is to allow for the lower frequency tones having images at 127x and 129x the tone frequency which will fall in the audio band for tones of frequency less than about 20kHz/128).
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WM8722
Advanced Information
LRCIN tBCH BCKIN tBCY DIN tDS tDH tBL tBCL tLB
Figure 1. Audio Data Input Timing
Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER BCKIN pulse cycle time BCKIN pulse width high BCKIN pulse width low BCKIN rising edge to LRCIN edge LRCIN rising edge to BCKIN rising edge DIN setup time DIN hold time SYMBOL tBCY tBCH tBCL tBL tLB tDS tDH TEST CONDITIONS MIN 100 40 40 20 20 20 20 TYP MAX UNIT ns ns ns ns ns ns ns Audio Data Input Timing Information
tSCKIL SCKI tSCKIH tSCKY
Figure 2. System Clock Timing Requirements
Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER System Clock Timing Information System clock pulse width high System clock pulse width low System clock cycle time tSCKIH tSCKIL tSCKY 10 10 27 ns ns ns SYMBOL TEST CONDITIONS MIN TYP MAX UNIT
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Advanced Information
WM8722
tMLL tMHH
LATCH
tMCY tMCH tMCL tMLD tMLS
MC tMDS MD tMDH LSB
Figure 3. Program Register Input Timing - 3-Wire MPU Serial Control Mode
Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER MC pulse cycle time MC pulse width low MD pulse width high MD set-up time MC hold time LATCH pulse width low LATCH pulse width high LATCH set-up time LATCH delay from MC SYMBOL tMCY tMCL tMCH tMDS tMDH tMLL tMHH tMLS tMLD TEST CONDITIONS MIN 100 40 40 20 20 20 20 20 20 TYP MAX UNIT ns ns ns ns ns ns ns ns ns Program Register Input Information
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WM8722
t3 MD t6 MC t1 t9 t7 t2 t3 t4
Advanced Information
t5
t8
Figure 4. Program Register Input Timing - 2-Wire MPU Serial Control Mode
Test Conditions AVDD, DVDD = 5V, AGND, DGND = 0V, TA = +25oC, fs = 48kHz, SCKI = 256fs unless otherwise stated. PARAMETER MC Frequency MC Low Pulsewidth MC High Pulsewidth Hold Time (Start Condition) Setup Time (Start Condition) Data Setup Time MD, MC Rise Time MD, MC Fall Time Setup Time (Stop Condition) Data Hold Time t1 t2 t3 t4 t5 t6 t7 t8 t9 600 900 SYMBOL TEST CONDITIONS MIN 0 600 1.3 600 600 100 300 300 TYP MAX 400 UNIT kHz ns us ns ns ns ns ns ns ns Program Register Input Information
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Advanced Information
WM8722
DEVICE DESCRIPTION
WM8722 is a complete low cost stereo audio DAC, including digital interpolation filter, multi-bit sigma delta with dither, and switched capacitor multi-bit stereo DAC and output smoothing filters. A novel multi-bit sigma-delta DAC design is used, utilising a 64x oversampling rate, to optimise signal-tonoise performance and increase clock jitter tolerance. The WM8722 also provides an analogue mixing function, which allows user-selectable control over mixing of an external analogue input signal (line level sources or microphone output) with the converted output signal. The device provides both line level and variable outputs. The WM8722 contains a high performance sine wave generator circuit, which can be used to generate low distortion sinusoidal waveforms of varying frequency and amplitude. The WM8722 uses a minimum of external components, with the internally generated midrail references used to provide DC bias of output signals requiring only a single external capacitor for decoupling purposes. The WM8722 is controlled through a software serial interface. This allows control of variables such as gain levels through each path, tone frequency and duration, and audio data interface format. The software control interface may be operated using either a 3-wire (SPI compatible) or 2-wire MPU interface. Selection of interface format is achieved by monitoring the state of BUSY pin at power up. In 2-wire mode, the ML pin becomes an address select, allowing two WM8722 devices to be used on the same bus. Operation using system clock of 256fs or 384fs is provided, selection between clock rates being automatically controlled. Alternatively, the user can select the clock rate through the software interface. Sample rates (fs) from less than 8ks/s to 96ks/s are allowed, provided the appropriate system clock is input. Tolerance of asynchronous word clock jitter is provided, the internal signal processing of the device re-synching to the external LRCIN clock once the phase difference between left-right and system clocks exceeds half a LRCIN period. During this re-synch period, the oversampling filters either miss an audio sample, or repeat the last sample value, so minimising the audible effects of this operation. The interface supports normal (Japanese right justified) and I2S (Philips left justified, one bit delayed) interface formats, in both packed and unpacked forms. (Packed has exactly the number of serial clocks corresponding to the number of data bits, per LRCIN period). Additionally the device automatically detects when it is connected to a 16 bit packed data source (32 serial clocks per LRCIN) and switches automatically into 16 bit mode. 44.1kHz de-emphasis is supported, with frequency scaling if other sample rates are used. The tone generator circuit uses a high quality sine weighted DAC, and sophisticated noise shaping techniques to achieve high quality tones with low noise and spurious tone generation. Using the nominal master tone clock (TCLK) frequency of 27MHz, any frequency from 1Hz to 32kHz may be generated in 1Hz increments. The duration of the tone burst may be programmed from 0.1second to 25.5 seconds. The next tone may be pre-programmed during a current tone burst, and is then loaded, in phase continuous manner at the end of the current tone so allowing continuous generation of varying frequency. The device is packaged in a small 5.3mm wide 20-pin SSOP package. Single 3V to 5.5V supplies may be used, the output amplitude scaling with absolute supply level. Low supply voltage operation and low current consumption, the low pin count small package and the analogue mixing features, make the WM8722 attractive for many consumer audio applications, including VCD, CD, DVD-Audio, set-top boxes and digital TV. Separate analogue and digital supply pins are provided, allowing 3V operation of digital and 5V operation of analogue circuits.
ANALOGUE MIXER
The analogue mixer circuits comprise signal paths to allow signal switching and gain adjust for each of the mixer line-in, DAC output, and tone generator signals. Additionally, mono signals can be created using the completely flexible switching arrangements, and 6dB attenuation switching circuits. Individual control bits are provided for each of the 5 switch inputs to each summing stage in the mixer, each signal path therefore being individually controllable. Any combination of output signals is therefore permissible. Fixed output level line outputs and volume adjusted variable output level outputs are provided.
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WM8722
TONE GENERATOR DAC
Advanced Information
The tone generator comprises a digital frequency synthesiser, which is used to create a clock at 128x the required tone frequency, and a 128 step per cycle, sine weighted DAC, which converts the clock into one of three tone types. An analogue programmable gain stage follows the DAC, allowing gain adjustment of the tone amplitude. Noise shaping techniques are used to create minimal spurious components in the frequency synthesiser. The WM8722 can generate three different tone types. The default setting is a sinusoidal tone. Square waves are generated by setting the SQR bit. Alternatively, a two-tone output that generates one cycle at the chosen frequency, followed by two cycles at twice that frequency can be selected by setting the F2F bit. This facility may be used in sine or square wave modes. The frequency of the resulting tone is controllable with 1Hz resolution, over a range of 1Hz to 32.767kHz, based on a TCLK frequency of 27MHz. Alternative tone clock frequencies may be used if required. For example the DAC SCLK frequency may be used, but in these cases the frequency range and resolution will change by the ratio of the clock used, to the nominal 27MHz clock specified. The duration of the selected tone is programmed via the serial interface. Once both the frequency and the duration have been set to non-zero values, the tone generation commences. Once the tone generator has started running, the next tone frequency and duration may be programmed ready to start as soon as the current tone finishes. Under this condition the tones are phase continuous, and a BUSY flag is set on the BUSY pin, which now becomes a CMOS output, overdriving any pull-up or down resistor placed on the pin to select the interface format at power-up. After a tone frequency of duration has been written, it may be over written with a new value if desired. At the conclusion of a tone burst, the circuit ensures that at the end of the duration time of the last tone, the tone continues to the next zero crossing point to ensure DC offsets are not created. A control bit (TFIN) is provided which allows selection of the method of completion of the burst: If set to 1, the burst completes at the next zero crossing. If left at 0, the burst completes a whole number of sinusoids, avoiding potential problems with DC levels changing across AC coupling capacitors. Whilst tones are being generated, writing either new frequency or new duration, will cause the subsequent burst to be generated phase continuously with the current burst. If a duration value of 0 is written during a burst, the current burst will stop immediately (at the next zero cross or full cycle complete point as selected by TFIN). If the current burst completes, and no new duration of frequency have been set, the tones stop and the duration value is reset to zero. The frequency setting is maintained in volatile memory. If a new duration is programmed, then the tone generator will re-start with the previously programmed frequency. If a new frequency is desired, the frequency is simply programmed before the duration, the tone commencing when the duration is written.
SYSTEM CLOCK
The system clock for the WM8722 must be either 256fs or 384fs where fs is the audio sampling frequency (LRCIN), typically 32kHz, 44.1kHz, 48kHz or 96kHz. The system clock is used to operate the digital filters and the noise shaping circuits. WM8722 has system clock detection circuitry that automatically determines the relationship between the system clock frequency and the sampling rate (to within 8 system clocks). If greater than 8 clocks error, then the interface shuts down the DAC and mutes the output. The system clock should be synchronised with LRCIN, but WM8722 is tolerant of phase differences or jitter on this clock. Severe distortion in the phase difference between LRCIN and the system clock (for example caused by too many or too few system clocks received per LRCIN period) will be detected, and cause the device to automatically re-synchronise. If the externally applied LRCIN slips in phase by more than half the internal LRCIN period, which is derived from the master clock, then the interface resynchronises. During re-synchronisation, the WM8722 will either repeat the previous sample or drop the next sample depending on the nature of the phase slip. This will ensure there is no discernible click at the analogue outputs during re-synchronisation.
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Advanced Information
WM8722
SAMPLING RATE (LRCIN) SYSTEM CLOCK FREQUENCY (MHZ) 256fs 384fs
32kHz 8.192 12.288 44.1kHz 11.2896 16.9340 48kHz 12.288 18.432 96kHz 24.576 36.864 Table 1 System Clock Frequencies versus Sampling Rate
AUDIO DATA INTERFACE
The serial data interface to WM8722 is fully compatible with both normal (MSB first, right-justified) or I2S interfaces. Data may be packed (number of serial BLCKS per LRCIN period is exactly 2 times the number of data bits, i.e. normally 32 in 16 bit mode) or unpacked (more than 32 BCLKs per LRCIN period. The WM8722 will automatically detect 16-bit packed data being sent to the device in normal mode, and accept the data in this input format accordingly. I2S MODE 0 1 Table 2. Serial Interface Formats DESCRIPTION Normal format (MSB-first, right justified) I2S format (Philips serial data protocol )
1/fs
LEFT CHANNEL LRCIN
RIGHT CHANNEL
BCKIN
DIN
1 MSB
2
3
n-2 n-1 n LSB
1
2
3
n-2 n-1 n LSB
MSB
Figure 5. Normal Data Input Timing
1/fs
LEFT CHANNEL LRCIN
RIGHT CHANNEL
BCKIN
DIN
1 MSB
2
3
n-2 n-1 n LSB
1
2
3
n-2 n-1 n LSB
MSB
Figure 6. I2S Data Input Timing
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WM8722
MODES OF OPERATION
Advanced Information
The software control interface may be operated using either a 3-wire (SPI-compatible) or 2-wire MPU interface. Selection of interface format is achieved by monitoring the state of BUSY pin at power up. In 3-wire mode, MD is used for the program data, MC is used to clock in the program data and LATCH is used to latch in the program data. In 2-wire mode, MD is used for serial data and MC is used for serial clock. In 2-wire mode, the LATCH pin allows the user to select one of two addresses.
SELECTION OF SERIAL CONTROL MODE
The serial control interface may be selected to operate in either 2 or 3-wire modes. This is achieved by setting the state of the BUSY pin at power-up with a weak, external pull-up or pull-down resistor (typically 10k). This pin is an input at power up, and its state selects the type of input format. The value input at power-up is sampled and stored internally. This allows the BUSY pin to be used as an output when tone generation has been enabled. This stored value is only reset when the device is powered off.
BUSY PIN (TONE GENERATION NOT ENABLED) 0 1
INTERFACE FORMAT 3 wire 2 wire
Table 3. Control Interface Mode Selection
3-WIRE (SPI COMPATIBLE) SERIAL CONTROL MODE
The WM8722 can be controlled using a 3-wire serial interface. MD is used for the program data, MC is used to clock in the program data and LATCH is use to latch in the program data. The 3-wire interface protocol is shown in Figure 7.
LATCH
MC
MD
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
Figure 7. 3-Wire Serial Interface
2-WIRE SERIAL CONTROL MODE
The WM8722 supports a 2-wire MPU serial interface. The device operates as a slave device only. The WM8722 has one of two slave addresses that are selected by setting the state of pin 5, (LATCH).
MD MC START
ADDR
R ADDR
R/W
ACK
DATA B15-8 ACK
DATA B7-0
ACK
STOP
Figure 8. 2-Wire Serial Interface
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Advanced Information
WM8722
LATCH STATE 1 0 Address 1000001 1000000
To control the WM8722 on the bus, the master must initiate a data transfer by establishing a start condition, defined by a high-to-low transition on MD whilst MC remains high. This indicates that an address and data transfer will follow. All peripherals respond to the start condition and shift the next eight bits (7-bit address + R/W bit). The transfer is MSB first. The peripheral that recognises the transmitted address responds by pulling the data line low during the ninth clock pulse (acknowledge bit). All other devices withdraw from the bus and maintain an idle condition once the appropriate peripheral has been recognised. The idle condition is where the device monitors the MD and MC lines waiting for a start condition and the correct transmitted address. The R/W bit determines the direction of data transfer. The WM8722 is a write only device and only responds to the R/W bit indicating a write. The WM8722 acts as a standard slave device on the bus. The data on the MD is clocked in by MC. The first 6 bits (which must be 100000) are clocked into the WM8722 followed by a programmable address bit to select one of the two available addresses. The eighth bit of the address byte is the R/W bit. The WM8722 checks this bit and responds if it is a write. If the correct address is sent by the master, the WM8722 acknowledges the bus master (ACK) and pulls the bus low. The next byte is the register address. Each subsequent byte of data is separated by an acknowledge bit. A stop condition is defined when there is a low-to-high transition on MD when MC is high. If a stop or start condition is detected out of sequence at any point in the data transfer, the device jumps to the idle condition.
SERIAL CONTROL OPERATION
Control of the various modes of operation is software control over the 2 or 3-wire serial interface. The following functions may be controlled via the serial control interface:
FUNCTION
OPTIONS
SOFTWARE CONTROL DEFAULT VALUE Normal format (0) 16 bit (0)
Input audio data format Input Word Length
Normal format I2S format 16 20 24 On Off Enable disable L, R, mono, Mute
De-emphasis selection
Off (0)
Operation enable (OPE) (power down) Analogue output mode
Enabled (0)
Stereo (1001)
Mute
On (Muted) Off (Un-muted) Lch/Rch = Hi/Lo Lch/Rch = Lo/Hi Lch, Rch individually Lch, Rch both
Off (0)
Input LRCIN polarity Master Volume Control
Lch/Rch = Hi/Lo (0) 0dB (1111001) Lch, Rch individually (0)
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WM8722
FUNCTION OPTIONS
Advanced Information SOFTWARE CONTROL DEFAULT VALUE 0dB (111111) Lch, Rch individually (0) 0dB (10111) Lch, Rch individually (0) Normal stereo (11100) MLMX left mux (11100) MLVMX left mux (11100) MRMX right mux (11100) MRVMX right mux M6DB bits all 0 (gain 0dB) 0dB (11111)
DAC digital volume
Lch, Rch individually Lch, Rch common Lch, Rch individually Lch, Rch both 5 switches for each of left and right, mix and volume paths, individually controlled, or both together, and with -6dB gain option for mono modes 0 to -46.5dB in 1.5dB steps plus mute 1 to 32767Hz in 1Hz steps (based on 27MHz TCLK) 0.1 to 25.5secs in 0.1sec steps
Mixer Volume Control
Mixer Output Selection
Tone amplitude
Tone frequency
0 = disabled
Tone duration
0 = disabled
Tone (TFIN)
Finish
Behaviour
1 = Full cycle sine wave 0 = next zero cross Sine or square wave 0 = sine 1 = square wave 0=f 1 = 2f
Tone Waveform
Tone Burst Table 4. Control Functions
f or 2f
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Advanced Information
WM8722
REGISTER MAP
The WM8722 controls the device functions using 15 program registers, each of which is 16-bits long. These registers are all loaded via the serial control interface in either 2 or 3-wire mode. There are two type of control word; either TFRQ, the tone frequency word, which is a single address bit followed by 15 data bits, or other types, which have 6 address bits, and 10 bits of data. Other types have the lead address bit inverted compared to TFREQ words, allowing use of a single write to load the required frequency.
REG TFREQ R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13
B15 1 0 0 0 0 0
B14
B13
B12 0 0 0 0 0
B11 0 0 0 0 1 1 1 1 0 0 0 0 1 1
B10 0 0 1 1 0 0 1 1 0 0 1 1 0 0
B9 0 1 0 1 0 1 0 1 0 1 0 1 0 1
B8 LDL LDR res BOTH BOTH BOTH BOTH BOTH BOTH BOTH BOTH res F2F
B7 F[14:0]
B6
B5
B4 DAL [7:0] DAR[7:0]
B3
B2
B1
B0
res res res
PL[3:0] res res res
IW1 res MUTE MUTE res
IW0 res
PWD ATC
DE LRP
MU I2S
MTRIML[4:0] MTRIMR[4:0] LVOL[6:0] RVOL[6:0]
RESERVED
0 0 0 0 0 0 0 0 0
RESERVED
0 0 0 1 1 1 1 1 1
ZCEN ZCEN res res res res SQR res res res res TFIN M6DB0 M6DB1 M6DB2 M6DB3
LMXSEL(4-0) RMXSEL(4-0) LVMXSEL(4-0) RVMXSEL(4-0) TTIM[7:0] TVOL[4:0]
MUTE
Table 5. Mapping of Program Registers
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WM8722
REGISTER NAME TFREQ Register 0 Register 1 1 000 0000 000 0001 REG ADDRESS BIT NAME F[14:0] DAL[7:0] LDL DAR[7:0] LDR MU DE PWD IW[1:0] PL[3:0] I2S LRP ATC MTRIML[4:0] MUTE MTRIMR[4:0] MUTE LVOL[6:0] ZCEN BOTH RVOL[6:0] ZCEN BOTH LMXSEL M6DB0 BOTH RMXSEL M6DB1 BOTH LVMXSEL M6DB2 BOTH RVMXSEL M6DB3 BOTH TTIM[7:0] TVOL[4:0] MUTE TFIN SQR F2F DESCRIPTION Tone frequency value DAC attenuation data for left channel Attenuation data load control for left channel DAC attenuation data for right channel Attenuation data load control for right channel Left and right DACs soft mute control De-emphasis control Power off control Input audio data bit length select Output mode select Audio data format select Polarity of LRCIN (pin 7) select Attenuator control Left mixer 1 attenuation data Left mixer mute Right mixer 1 attenuation data Right mixer mute Left volume 2 attenuation data
Advanced Information
DEFAULT VALUE 000 0000 0000 0000 111 1111 (0dB) 0 111 1111 (0dB) 0 0 (not muted) 0 (de-emph off) 0 (power on) 00 (16 bit) 1001 (normal stereo) 0 ( NORMAL format) 0 0 10111 (0dB) 0 (not mute) 10111 (0dB) 0 (not mute) 1111 001 (0dB)
Register 2
000 0010
Register 3
000 0011
Register 4 Register 5 Register 6
000 0100 000 0101 000 0110
Register 7
000 0111
Right volume 2 attenuation data
1111 001 (0dB)
Register 8
000 1000
Left mixer output mux control M6DB for left mix output Right mixer output mux control M6DB for right mix output Left variable output mux control M6DB for left variable output Right variable output mux control M6DB for right variable output Tone duration Tone amplitude Tone mute Tone burst finish on zero cross Tone sine or square wave Tone one cycle at F, two cycle at 2xF
11100 (normal stereo) 0 (0dB) 11100 (normal stereo) 0 (0dB) 11100 (normal stereo) 0 (0dB) 11100 (normal stereo) 0 (0dB) 000 0000 (no tone) 11111 (max output) 0 (not muted) 0 (finish on full cycle) 0 (sine wave) 0 (normal F)
Register 9
000 1001
Register 10
000 1010
Register 11
000 1011
Register 12 Register 13
000 1100 000 1101
Table 6. Internal Register Mapping
REGISTER TFREQ
TONE FREQUENCY
This is the special register of 15 bit length with a single bit address, to allow values for the selected tone frequency from 1Hz to 32767Hz to be written in one word. Writing 0 turns off the tone. FTONE = (FTCLK x TFREQ [15:0])/27x106
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Advanced Information
WM8722
DAC OUTPUT ATTENUATION
A digital attenuator is provided to allow the levels of DAC signals to be attenuated in the digital domain. Register 0 (A[1:0] = 00) is used to control left channel attenuation. Bits 0-7 (AL[7:0]) are used to determine the attenuation level. The level of attenuation is given by: Attenuation = [20.log10 (Attenuation_Data/255)] dB Bit 8 in register 0 (LDL) is used to control the loading of attenuation data in B[7:0]. When LDL is set to 0, attenuation data will be loaded into AL[7:0], but it will not affect the attenuation level until LDL is set to 1. LDR in register 1 has the same function for right channel attenuation. Attenuation levels are controlled by setting the register set AL[7:0] (left channel) or AR[7:0] (right channel). Attenuation levels are given in Table 7. AX[7:0] 00h 01h : : : FEh FFh Table 7. Attenuation Control Levels Register 1 (A[1:0] = 01)is used to control right channel attenuation in a similar manner. ATTENUATION LEVEL - dB (Mute) -48.16 dB : : : -0.034 dB 0dB
REGISTER 0/1
REGISTER 2
SOFT MUTE
Soft mute is controlled by setting bit 0 in register 2 (A[1:0]=10). A high level on bit 0 will cause the DAC outputs to be muted, the effect of which is to ramp the signal down in the digital domain so that there is no discernible click.
DIGITAL DE-EMPHASIS
Bit 1 (DE) in register 2 (A[1:0]=10) is used to control digital de-emphasis. A low level on bit 1 disables de-emphasis whilst a high level enables de-emphasis.
POWER OFF CONTROL
Bit 2 (PWD) in register 2 is used for operation control. With PWD = low (default) the device functions normally. With PWD = high the device is disabled and the outputs are held at midrail. Current consumption of the digital section is minimised, but analogue bias sections remain active in order to preserve DC levels.
INPUT WORD RESOLUTION
Bits 3 and 4 of register 2 (IW[1:0]) are used to determine the input word resolution. The WM8722 supports 16-bit, 18-bit, 20-bit and 24-bit word formats.
BIT 4 (IW1) 0 0 1 1
BIT 3 (IW0) 0 1 0 1
INPUT RESOLUTION 16-bit Data Word 20-bit Data Word 24-bit Data Word 18-bit Data Word
Table 8. Input Data Resolution
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WM8722
DAC OUTPUT CONTROL
Bits 5, 6, 7 and 8 (PL[3:0]) of register 2 are used to control the output format.
Advanced Information
PL0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
PL1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
PL2 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
PL3 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
LEFT OUTPUT MUTE MUTE MUTE MUTE R R R R L L L L (L + R)/2 (L + R)/2 (L + R)/2 (L + R)/2
RIGHT OUTPUT MUTE R L (L + R)/2 MUTE R L (L + R)/2 MUTE R L (L + R)/2 MUTE R L (L + R)/2
NOTE Mute Both Channels
Reverse Channels
Stereo Mode
Mono Mode
Table 9. Programmable Output Format
REGISTER 3
AUDIO DATA INPUT FORMAT
WM8722 allows maximum flexibility over the control of the audio data interface, allowing selection of format type, word length, and sample rates.
DIGITAL AUDIO SERIAL PROTOCOL
A low on bit 0 sets the format to Normal (MSB-first, right justified Japanese format), whilst a high sets the format to I2S (Philips serial data protocol).
AUDIO INTERFACE CLOCKS
Bit 1 (LRP) of register 3 is used to control the polarity of LRCIN (sample rate clock). When bit 1 is low, left channel data is assumed when LRCIN is in a high phase and right channel data is assumed when LRCIN is in a low phase. When bit 1 is high, the polarity assumption is reversed.
ATTENUATOR CONTROL
Bit 2 in register 3 (A1[1:0] = 11) is used to control the attenuator (ATC). When ATC is high, the attenuation data loaded in program register 0 is used for both the left and the right channels. When ATC is low, the attenuation data for each register is applied separately to left and right channels.
REGISTER 4/5
ANALOGUE MIXER TRIM
Bits 0-4 of register 4, MTRIML[0:4], set the gain level of the first stage of analogue mixing on the left channel. The 5-bit register selects 1.5 dB increments of the MIXINL signal, over a range of +12dB to -34.5dB. A 6th bit, MUTE, controls muting of the signal when set high. Similarly, bits 0-4 of register 5, MTRIMR[0:4], set the attenuation level of the first stage of analogue mixing on the right channel. The 5-bit register allows 1.5 dB increments of the MIXINR signal, over a range of +12dB to -34.5dB. A 6th bit, MUTE, controls muting of the signal when set high.
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Advanced Information
WM8722
BOTH
In register 4 and 5, a further bit BOTH is available: When a write is made to either register 4 or 5 and BOTH is set high, then the same value written to the register will also be written into the other register. This allows both Left and Right channel gains to be updated simultaneously, halving the number of serial writes required, (simplifying gain ramping, for example) provided that the same gain is needed for both channels.
REGISTER 6/7
VOLUME CONTROL
Bits 0-6 of register 6, LVOL[6:0], control gain applied to the variable level output VAROUTL. This 6bit register controls 1.0 dB increments of the volume, over a range of +6 dB to -73 dB. Similarly bits 0-6 of register 7, RVOL[6:0], control the gain applied to the variable level output VAROUTR. Value 1111111 sets maximum, i.e. 6dB gain. Code 48 sets minimum gain. Values less than code 48 apply mute to the gain stage. (i.e. set volume to 000 0000 to achieve mute)
ZCEN
A zero cross detect circuit is provided, so that volume control values are only updated when the input signal to the gain stage is close to the analogue ground level, minimising clicks and zipper noise as the gain values are changed. This circuit has no time out so if DC levels are being applied to the gain stage input, then the gain will not be updated. This zero cross function is enabled when the ZCEN bit is set high during a volume register write. If there is concern that a DC level may have blocked a volume change (one made with ZCEN set high), then a subsequent volume write of the same value, but with the ZCEN bit set low will force a volume update regardless of the DC level.
BOTH
In register 6 and 7, a further bit BOTH is available. When a write is made to either register 6 or 7 and BOTH is set high, then the same value written to the register will also be written into the other register. This allows both Left and Right channel gains to be updated simultaneously, halving the number of serial writes required, provided that the same gain is needed for both channels.
REGISTER 8, 9, 10, 11
ANALOGUE MIXER OUTPUT SELECTION
The WM8722 allows software controllable selection of signal outputs. The WM8722 allows 2 outputs per channel, with one output at line level, and another output at variable level, according to the LVOL[6:0] and RVOL[6:0] attenuation register settings. In addition, the user may select whether the left or the right signal, converted in the DAC, is mixed with the corresponding mixer input or not. This switching scheme is detailed in Figure 9, with 10 different select signals per channel, 5 each for each Mux: Each Mux therefore has 5 input signals; DACL, DACR, MIXL, MIXR and TONE. This allows completely flexible selection of signal paths, both mono and stereo outputs, on any output.
MUX CONTROL BITS MXSEL(4:0) 0 1 2 3 4
SIGNAL SELECTED WHEN HIGH IS SET DAC sum enable MIXIN sum enable TONE in sum enable Opposite channel DAC sum enable Opposite channel MIXIN sum enable
Table 10. MUX(4:0) mux control switches If mono outputs are selected, the gain through the summer amplifiers may be reduced by 6dB if required by setting the appropriate M6DB bits. Similarly left and right channels may be completely swapped.
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WM8722
Advanced Information
MXINL
+
LEFT DAC
0/-6dB
LINEOUTL
+
0/-6dB
VAROUTL
L Mix Switches (0-9) R Mix Switches (0-9)
+
RIGHT DAC
0/-6dB
VAROUTR
+
0/-6dB
LINEOUTR
TONE DAC MXINR
Figure 9. Output Mixer Configuration
M6DB
In each of the 4 MUX control registers there is an M6DB bit relevant to that channel. Setting M6DB high reduces the relevant output signal by 6dB.
BOTH
When a write to any MXSEL register is made with the BOTH bit set high, then the complementary channel MXSEL register for the other channel is updated with the same value. For example, if RVMXSEL is updated and BOTH is set, then LVMXSEL is updated with the same value, but the RMXSEL and LMXSEL registers (the non variable output path muxes) are NOT updated.
REGISTER 12
TONE DURATION
Bits 0-7 of register 12 sets the duration of the tone burst. Writing to the register with a non-zero value starts the tone burst. Wring zero to this register stops the tone. T = (2.7x106 x TTIM[7:0])/ FTCLK
REGISTER 13
TONE GENERATOR GAIN CONTROL
Bits 0-4 of register 13 TVOL[0:4] set the gain level of the tones summed into the analogue outputs. Bit 5 of this word controls muting of the tones. Note both mute must be off (0) and the tone input to the relevant mixer summing path must be selected (1). The gain defaults to 0dB (11111) but may be attenuated n 1.5dB steps down to -46.5dB.
TONE GENERATOR WAVEFORM CONTROL TFIN
A control bit (TFIN) is provided which allows selection of the method of completion of the burst. If set to 1, the burst completes at the next zero crossing. If left at 0, the burst completes a whole number of sinusoids, avoiding potential problems with DC levels changing across AC coupling capacitors. At the conclusion of a tone burst, the circuit ensures that at the end of the duration time of the last tone, the tone continues to the next zero crossing point to ensure DC offsets are not created.
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Advanced Information
WM8722
SQR
The WM8722 can generate three different tone types. The default setting is a sinusoidal tone. Square waves are generated by setting the SQR bit.
F2F
A two-tone output that generates one cycle at the chosen frequency, followed by two cycles at twice that frequency can be selected by setting the F2F bit. This facility may be used in sine or square wave modes.
SYSTEM DIAGRAM
VIDEO DAC VIDEO OUT TONE GENERATOR OUTPUT MEDIA FRONT END WM8722 AUDIO DAC L R L R SYSTEM CLOCKS STORAGE (HDD) LINE LEVEL AUDIO OUTPUT (VCR) AMPLIFIER HEADPHONE OUT MIC OR ANALOGUE INPUT VARIABLE LEVEL AUDIO OUTPUT (TV) MONO AUDIO OUTPUT (OPTIONAL) DIGITAL DECODER
HOME CONNECTIVITY
Figure 10. Digital Set Top Box Application The WM8722 is a complete audio sub-system designed for digital set top box applications. A typical application might require audio outputs to be routed to a VCR and television. The WM8722 allows the user to control the output audio level being sent to the television whilst maintaining a constant volume level to the VCR. The on-board tone generator can be programmed to provide a audible warning signal from the set top box to the television outputs without appearing on the line level outputs. The WM8722 can also directly generate a mono signal for UHF outputs. The WM8722 contains a stereo analogue input. This signal can be routed or mixed together onto the line and variable outputs. It can be used to control the volume level of an audio output from another audio source such as a games machine or additional set top box. Alternatively, it could be used to provide a karaoke input from a digital effects processor.
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WM8722 RECOMMENDED EXTERNAL COMPONENTS
Advanced Information
DVDD 6 + C1 C2 16 DGND AGND 10 C3 DVDD AVDD 11
AVDD + C4
DGND
AGND
2
MC MD LATCH BUSY VAROUTL VAROUTR 9 C5
SPI or 2-wire Interface
DVDD
3 4 5
2-wire Interface SPI Interface
DGND R1
12
C6
AC-Coupled Variable Outputs to External LPF
+ +
WM8722
1 17 18 TCLK LINEOUTR DIN LRCIN LINEOUTL BCKIN SCKI 13 8 C7
C8
Audio Serial Data I/F
19 20
AC-Coupled Line Level outputs to External LPF
+ +
C9
7
MIXINR
CAP
15 + C11 C12
C10
14
MIXINL AGND
NOTES:
1. AGND and DGND should be connected as close to the WM8722 as possible. 2. C2, C3, C9, C10 and C11 should be positioned as close to the WM8722 as possible. 3. Capacitor types should be carefully chosen. Capacitors with very low ESR are recommended for optimum performance.
Figure 11. External Components Diagram
RECOMMENDED EXTERNAL COMPONENTS VALUES
COMPONENT REFERENCE C1 and C4 C2 and C3 C5, C6, C7 and C8 C11 C12 R1 C9,C10 SUGGESTED VALUE 10F 0.1F 10F 0.1F 10F 10k 1F AC coupling capacitors for setting DC inputs level of analogue DESCRIPTION De-coupling for DVDD and AVDD. De-coupling for DVDD and AVDD. Output AC coupling caps to remove midrail DC level from outputs. Reference de-coupling capacitors for CAP pin.
Table 11. External Components Description
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Advanced Information
WM8722
PACKAGE DIMENSIONS
DS: 20 PIN SSOP (7.2 x 5.3 x 1.75 mm) DM0015.A
b
20
e
11
E1
E
GAUGE PLANE 1 10
D 0.25 c A A2 A1 -C0.10 C
SEATING PLANE
L
Symbols A A1 A2 b c D e E E1 L REF: MIN ----0.05 1.65 0.22 0.09 6.90 7.40 5.00 0.55 o 0
Dimensions (mm) NOM --------1.75 --------7.20 0.65 BSC 7.80 5.30 0.75 o 4 JEDEC.95, MO-150
MAX 2.0 ----1.85 0.38 0.25 7.50 8.20 5.60 0.95 o 8
NOTES: A. ALL LINEAR DIMENSIONS ARE IN MILLIMETERS. B. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE. C. BODY DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSION, NOT TO EXCEED 0.20MM. D. MEETS JEDEC.95 MO-150, VARIATION = AE. REFER TO THIS SPECIFICATION FOR FURTHER DETAILS.
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