LM4546B AC ’97 Rev 2 Multi-Channel Audio Codec with Sample Rate Conversion and National 3D Sound General Description Key Specifications The LM4546B is an audio codec for PC systems which is fully PC99 compliant and performs the analog intensive functions of the AC ’97 Rev 2.1 architecture. Using 18-bit Sigma-Delta ADCs and DACs, the LM4546B provides 90 dB of Dynamic Range. The LM4546B was designed specifically to provide a high quality audio path and provide all analog functionality in a PC audio system. It features full duplex stereo ADCs and DACs and analog mixers with access to 2 stereo and 2 mono inputs. Each mixer input has separate gain, attenuation and mute control and the mixers drive 1 mono and 1 stereo output, each with attenuation and mute control. The LM4546B supports National’s 3D Sound stereo enhancement and a comprehensive sample rate conversion capability. The sample rate for the ADCs and DACs can be programmed separately with a resolution of 1 Hz to convert any rate in the range 4 kHz – 48 kHz. Sample timing from the ADCs and sample request timing for the DACs are completely deterministic to ease task scheduling and application software development. These features together with an extended temperature range also make the LM4546B suitable for non-PC codec applications. The LM4546B features the ability to connect several codecs together using the Extended AC Link configuration of one dedicated serial data signal to the Controller per codec. LM4546B systems support up to 8 simultaneous channels of streaming data on Input Frames (Codec to Controller) while Output Frames (Controller to Codec) carry 2 streams to multiple codecs. The LM4546B may also be used in systems with the National LM4550 to support up to 6 simultaneous channels of streaming data on Output Frames. The AC ’97 architecture separates the analog and digital functions of the PC audio system allowing both for system design flexibility and increased performance. n Analog Mixer Dynamic Range n DAC Dynamic Range n ADC Dynamic Range © 2006 National Semiconductor Corporation DS201233 97 dB (typ) 89 dB (typ) 90 dB (typ) Features n AC ’97 Rev 2.1 compliant n High quality Sample Rate Conversion from 4 kHz to 48 kHz in 1 Hz increments n Multiple codec support n National’s 3D Sound stereo enhancement circuitry n Advanced power management support n Digital 3.3V and 5V supply options n Extended Temperature: −40˚C ≤ TA ≤ 85˚C Applications n Desktop PC audio systems on PCI cards, AMR cards, or with motherboard chips sets featuring AC Link n Portable PC systems as on MDC cards, or with a chipset or accelerator featuring AC Link n General and Multi-channel audio frequency systems n Automotive telematics www.national.com LM4546B AC ’97 Rev 2 Multi-Channel Audio Codec with Sample Rate Conversion and National 3D Sound September 2006 www.national.com 2 Block Diagram 20123301 LM4546B Soldering Information LQFP Package If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Vapor Phase (60 sec.) 6.0V Storage Temperature 215˚C Infrared (15 sec.) 220˚C θJA (typ) – VBH48A 74˚C/W −65˚C to +150˚C −0.3V to VDD +0.3V Input Voltage ESD Susceptibility (Note 2) pin 3 Operating Ratings 2000V Temperature Range 750V ESD Susceptibility (Note 3) pin 3 Junction Temperature TMIN ≤ TA ≤ TMAX (Note 4) 200V −40˚C ≤ TA ≤ 85˚C 100V Analog Supply Range 4.2V ≤ AVDD ≤ 5.5V 150˚C Digital Supply Range 3.0V ≤ DVDD ≤ 5.5V Electrical Characteristics (Notes 1, 5) The following specifications apply for AVDD = 5V, DVDD = 3.3V, Sampling Frequency (Fs) = 48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for TA= 25˚C. The reference for 0 dB is 1 Vrms unless otherwise specified. Symbol Parameter Typical (Note 6) AVDD Analog Supply Range DVDD Digital Supply Range Units (Limits) LM4546B Conditions Limit (Note 7) 4.2 V (min) 5.5 V (max) 3.0 V (min) 5.5 V (max) DVDD = 5 V 34 mA DVDD = 3.3 V 19 mA 53 mA 19 µA 70 µA DIDD Digital Quiescent Power Supply Current AIDD Analog Quiescent Power Supply Current IDSD Digital Shutdown Current PR543210 = 111111 IASD Analog Shutdown Current PR543210 = 111111 VREF Reference Voltage No pullup resistor PSRR Power Supply Rejection Ratio 2.16 V 40 dB Analog Loopthrough Mode (Note 8) THD Dynamic Range (Note 9) CD Input to Line Output, -60 dB Input THD+N Total Harmonic Distortion VO = -3 dB, f = 1 kHz, RL = 10 kΩ 97 90 dB (min) 0.013 0.02 % (max) Analog Input Section VIN Line Input Voltage LINE_IN, AUX, CD, VIDEO, PC_BEEP, PHONE 1 Vrms VIN Mic Input with 20 dB Gain 0.1 Vrms VIN Mic Input with 0 dB Gain 1 Vrms Xtalk Crosstalk CD Left to Right -95 ZIN Input Impedance (Note 9) All Analog Inputs 40 10 kΩ (min) CIN Input Capacitance(Note 9) 3.7 7 pF Interchannel Gain Mismatch dB CD Left to Right 0.1 dB 0 dB to 22.5 dB 1.5 dB 86 dB 1.5 dB 86 dB Record Gain Amplifier - ADC AS Step Size AM Mute Attenuation (Note 9) Mixer Section AS Step Size AM Mute Attenuation +12 dB to -34.5 dB 3 www.national.com LM4546B Absolute Maximum Ratings (Note 1) LM4546B Electrical Characteristics (Notes 1, 5) The following specifications apply for AVDD = 5V, DVDD = 3.3V, Sampling Frequency (Fs) = 48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for TA= 25˚C. The reference for 0 dB is 1 Vrms unless otherwise specified. (Continued) Symbol Parameter Units (Limits) LM4546B Conditions Typical (Note 6) Limit (Note 7) Analog to Digital Converters Resolution 18 Dynamic Range (Note 9) -60 dB Input THD+N, A-Weighted 90 Frequency Response -1 dB Bandwidth 20 Dynamic Range (Note 9) -60 dB Input THD+N, A-Weighted 89 Total Harmonic Distortion VIN = -3 dB, f = 1 kHz, RL = 10 kΩ Bits 86 dB (min) kHz Digital to Analog Converters Resolution THD 18 Frequency Response Group Delay (Note 9) Sample Freq. = 48 kHz Out of Band Energy (Note 10) DT Bits 82 dB (min) 0.01 % 20 - 21 k Hz 0.36 1 ms (max) -40 dB Stop Band Rejection 70 dB Discrete Tones -96 dB 1.5 dB 86 dB 220 Ω Analog Output Section AS Step Size AM Mute Attenuation ZOUT Output Impedance (Note 9) 0 dB to -46.5 dB All Analog Outputs Digital I/O (Note 9) VIH High level input voltage 0.65 x DVDD V (min) VIL Low level input voltage 0.35 x DVDD V (max) VOH High level output voltage IO = −2.5 mA. 0.90 x DVDD V (min) VOL Low level output voltage IO = 2.5 mA. 0.10 x DVDD V (max) ± 10 ± 10 µA 7.5 pF(Max) IL Input Leakage Current AC Link inputs IL Tri state Leakage Current High impedance AC Link outputs Cin AC-Link I/O capacitance SDout, BitClk, SDin, Sync, Reset# only 4 IDR Output drive current AC Link outputs 5 mA 12.288 MHz 81.4 ns µA Digital Timing Specifications (Note 9) FBC BIT_CLK frequency TBCP BIT_CLK period Variation of BIT_CLK duty cycle from 50% ± 20 TCH BIT_CLK high FSYNC SYNC frequency TSP SYNC period 20.8 µs TSH SYNC high pulse width 1.3 µs TSL SYNC low pulse width TDSETUP Setup Time for codec data input SDATA_OUT to falling edge of BIT_CLK 3.5 10 ns (min) TDHOLD Hold Time for codec data input Hold time of SDATA_OUT from falling edge of BIT_CLK 5.3 10 ns (min) TSSETUP Setup Time for codec SYNC input SYNC to falling edge of BIT_CLK 3.8 10 ns (min) Hold Time for codec SYNC input Hold time of SYNC from falling edge of BIT_CLK 10 ns (min) TSHOLD www.national.com 48 kHz 19.5 4 % (max) µs Symbol Parameter Conditions Units (Limits) LM4546B Typical (Note 6) Limit (Note 7) 5.2 15 ns (max) TCO Output Valid Delay Output Delay of SDATA_IN from rising edge of BIT_CLK TRISE Rise Time BIT_CLK, SYNC, SDATA_IN or SDATA_OUT 6 ns (max) TFALL Fall Time BIT_CLK, SYNC, SDATA_IN or SDATA_OUT 6 ns (max) TRST_LOW RESET# active low pulse width For Cold Reset 1.0 µs (min) TRST2CLK RESET# inactive to BIT_CLK start up For Cold Reset 162.8 ns (min) 271 TSH SYNC active high pulse width For Warm Reset 1.0 µs (min) TSYNC2CLK SYNC inactive to BIT_CLK start up For Warm Reset 162.8 ns (min) TS2_PDOWN AC Link Power Down Delay Delay from end of Slot 2 to BIT_CLK, SDATA_IN low 1 µs (max) TSUPPLY2RST Power On Reset Time from minimum valid supply levels to end of Reset 1 µs (min) TSU2RST Setup to trailing edge of RESET# For ATE Test Mode 15 ns (min) TRST2HZ Rising edge of RESET# to Hi-Z For ATE Test Mode 25 ns (max) Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 2: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Note 3: Machine Model, 220 pF – 240 pF discharged through all pins. Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum allowable power dissipation is PDMAX = (TJMAX– TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4546B, TJMAX = 150˚C. The typical junction-to-ambient thermal resistance is 74˚C/W for package number VBH48A. Note 5: All voltages are measured with respect to the ground pin, unless otherwise specified. Note 6: Typicals are measured at 25˚C and represent the parametric norm. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level). Note 8: Loopthrough mode describes a path from an analog input through the analog mixers to an analog output. Note 9: These specifications are guaranteed by design and characterization; they are not production tested. Note 10: Out of band energy is measured from 28.8 kHz to 100 kHz relative to a 1 Vrms DAC output. 5 www.national.com LM4546B Electrical Characteristics (Notes 1, 5) The following specifications apply for AVDD = 5V, DVDD = 3.3V, Sampling Frequency (Fs) = 48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for TA= 25˚C. The reference for 0 dB is 1 Vrms unless otherwise specified. (Continued) LM4546B Timing Diagrams Clocks Data Delay, Setup and Hold 20123310 20123311 Digital Rise and Fall Legend 20123330 20123312 Power On Reset 20123329 Cold Reset 20123313 Warm Reset 20123314 www.national.com 6 LM4546B Typical Application 20123303 FIGURE 1. LM4546B Typical Application Circuit, Single Codec, 1 Vrms inputs APPLICATION HINTS • The LM4546B must be initialized by using RESET# to perform a Power-On-Reset as shown in the Power On Reset Timing Diagram • Don’t leave unused analog inputs floating. Tie all unused inputs together and connect to Analog Ground through a capacitor (e.g. 0.1 µF) • Do not leave CD_GND floating when using the CD stereo input. CD_GND is the AC signal reference for the CD channels and should be connected to the CD source ground (Analog Ground may also be acceptable) through a 1 µF capacitor • If using a non-standard AC Link controller take care to keep the SYNC and SDATA_IN signals low during Cold Reset to avoid accidentally activating the ATE or Vendor test modes • The PC_Beep input should be explicitly muted if not used since it defaults to 0 dB gain on reset, unlike the mute default of the other analog inputs 7 www.national.com www.national.com 8 (Continued) FIGURE 2. LM4546B Reference Design, Typical Application, Single Codec, 1 Vrms and 2 Vrms inputs, EMC output filters Typical Application 20123325 LM4546B LM4546B Connection Diagram 20123302 Top View Order Number LM4546BVH See NS Package Number VBH48A Pin Descriptions ANALOG I/O Name PC_BEEP PHONE CD_L Pin 12 13 18 I/O Functional Description I Mono Input This line level (1 Vrms nominal) mono input is mixed equally into both channels of the Stereo Mix signal at MIX2 under the control of the PC_Beep Volume control register, 0Ah. The PC_BEEP level can be muted or adjusted from 0 dB to -45 dB in 3 dB steps. The Stereo Mix signal feeds both the Line Out and Line Level Out analog outputs and is also selectable at the Record Select Mux. I Mono Input This line level (1 Vrms nominal) mono input is mixed equally into both channels of the Stereo Mix signal at MIX2 under the control of the Phone Volume register, 0Ch. The PHONE level can be muted or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. The Stereo Mix signal feeds both the Line Out and Line Level Out analog stereo outputs and is also selectable at the Record Select Mux. I Left Stereo Channel Input This line level input (1 Vrms nominal) is selectable at the left channel of the stereo Input Mux for conversion by the left channel ADC. It can also be mixed into the left channel of the Stereo Mix 3D signal at MIX1 under the control of the CD Volume register, 12h. The CD_L level can be muted (along with CD_R) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is mixed into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out. 9 www.national.com LM4546B Pin Descriptions (Continued) ANALOG I/O (Continued) Name CD_GND CD_R MIC1 MIC2 LINE_IN_L LINE_IN_R www.national.com Pin 19 20 21 22 23 24 I/O Functional Description I AC Ground Reference This input is the reference for the signals on both CD_L and CD_R. CD_GND is NOT a DC ground and should be AC-coupled to the stereo source ground common to both CD_L and CD_R. The three inputs CD_GND, CD_L and CD_R act together as a quasi-differential stereo input with CD_GND providing AC common-mode feedback to reject ground noise. This can improve the input SNR for a stereo source with a good common ground but precision resistors may be needed in any external attenuators to achieve the necessary balance between the two channels. I Right Stereo Channel Input This line level input (1 Vrms nominal) is selectable at the right channel of the stereo Input Mux for conversion by the right channel ADC. It can also be mixed into the right channel of the Stereo Mix 3D signal at MIX1 under the control of the CD Volume register, 12h. The CD_R level can be muted (along with CD_L) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out. I Mono microphone input Either MIC1 or MIC2 can be muxed to a programmable boost amplifier with selection by the MS bit (bit D8) in the General Purpose register, 20h. The boost amplifier gain (0 dB or 20 dB) is set by the 20dB bit (D6) in the Mic Volume register, 0Eh. Nominal input levels at the two gain settings are 1 Vrms and 0.1 Vrms respectively. The amplifier output is selectable (Record Select register, 1Ah) by either the right or left channels of the Record Select Mux for conversion on either or both channels of the stereo ADC. The amplifier output can also be accessed at the stereo mixer MIX1 (muting and mixing adjustments via Mic Volume register, 0Eh) where it is mixed equally into both left and right channels of Stereo Mix 3D for access to the stereo outputs Line Out and Line Level Out. Access to the Mono analog output is selected by a mux controlled by the MIX bit (D9) in General Purpose register, 20h. I Mono microphone input Either MIC1 or MIC2 can be muxed to a programmable boost amplifier with selection by the MS bit (bit D8) in the General Purpose register, 20h. The boost amplifier gain (0 dB or 20 dB) is set by the 20dB bit (D6) in the Mic Volume register, 0Eh. Nominal input levels at the two gain settings are 1 Vrms and 0.1 Vrms respectively. The amplifier output is selectable (Record Select register, 1Ah) by either the right or left channels of the Record Select Mux for conversion on either or both channels of the stereo ADCs. The amplifier output can also be accessed at the stereo mixer MIX1 (muting and mixing adjustments via Mic Volume register, 0Eh) where it is mixed equally into both left and right channels of Stereo Mix 3D for access to the stereo outputs Line Out and Line Level Out. Access to the Mono analog output is selected by a mux controlled by the MIX bit (D9) in General Purpose register, 20h. I Left Stereo Channel Input This line level input (1 Vrms nominal) is selectable at the left channel of the stereo Record Select Mux for conversion by the left channel ADC. It can also be mixed into the left channel of the Stereo Mix 3D signal at MIX1 under the control of the Line In Volume register, 10h. The LINE_IN_L level can be muted (along with LINE_IN_R) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out. I Right Stereo Channel Input This line level input (1 Vrms nominal) is selectable at the right channel of the stereo Input Mux for conversion by the right channel ADC. It can also be mixed into the right channel of the Stereo Mix 3D signal at MIX1 under the control of the Line In Volume register, 10h. The LINE_IN_R level can be muted (along with LINE_IN_L) or adjusted from +12 dB to -34.5 dB in 1.5 dB steps. Stereo Mix 3D is combined into the Stereo Mix signal at MIX2 for access to the stereo outputs Line Out and Line Level Out. 10 LM4546B Pin Descriptions (Continued) ANALOG I/O (Continued) Name LINE_OUT_L LINE_OUT_R MONO_OUT Pin 35 36 37 I/O Functional Description O Left Stereo Channel Output This line level output (1 Vrms nominal) is fed from the left channel of the Stereo Mix signal from MIX2 via the Master Volume register, 02h. The LINE_OUT_L amplitude can be muted (along with LINE_OUT_R) or adjusted from 0 dB to -46.5 dB in 1.5 dB steps. O Right Stereo Channel Output This line level output (1 Vrms nominal) is fed from the right channel of the Stereo Mix signal from MIX2 via the Master Volume register, 02h. The LINE_OUT_R amplitude can be muted (along with LINE_OUT_L) or adjusted from 0 dB to -46.5 dB in 1.5 dB steps. O Mono Output This mono line level output (1 Vrms nominal) is fed from either a microphone input (MIC1 or MIC2, after boost amplifier) or from the mono sum of the left and right Stereo Mix 3D channels from MIX1. The optional National 3D Sound enhancement can be disabled (default) by the 3D bit (bit D13) in the General Purpose register, 20h. Choice of input is by the MIX bit (D9) in the same register. MIX=0 selects a microphone input. Output level can be muted or adjusted from 0 dB to -46.5 dB in 1.5 dB steps via the Mono Volume register, 06h. DIGITAL I/O AND CLOCKING Name XTL_IN XTL_OUT SDATA_OUT BIT_CLK SDATA_IN Pin 2 3 5 6 8 I/O Functional Description I 24.576 MHz crystal or oscillator input To complete the oscillator circuit use a fundamental mode crystal operating in parallel resonance and connect a 1MΩ resistor across pins 2 and 3. Choose the load capacitors (Figure 2, C1, C2) to suit the load capacitance required by the crystal (e.g. C1 = C2 = 33 pF for a 20 pF crystal Assumes that each ’Input + trace’ capacitance = 7 pF). This pin may also be used as the input for an external oscillator (24.576 MHz nominal) at standard logic levels (VIH, VIL). This pin is only used when the codec is in Primary mode. It may be left open (NC) for any Secondary mode. O 24.576 MHz crystal output Used with XTAL_IN to configure a crystal oscillator. When the codec is used with an external oscillator this pin should be left open (NC). When the codec is configured in a Secondary mode this pin is not used and may be left open (NC). I Input to codec This is the input for AC Link Output Frames from an AC ’97 Digital Audio Controller to the LM4546B codec. These frames can contain both control data and DAC PCM audio data. This input is sampled by the LM4546B on the falling edge of BIT_CLK. I/O AC Link clock An OUTPUT when in Primary Codec mode. This pin provides a 12.288 MHz clock for the AC Link. The clock is derived (internally divided by two) from the 24.576 MHz signal at the crystal input (XTL_IN). This pin is an INPUT when the codec is configured in any of the Secondary Codec modes and would normally use the AC Link clock generated by a Primary Codec. O Output from codec This is the output for AC Link Input Frames from the LM4546B codec to an AC ’97 Digital Audio Controller. These frames can contain both codec status data and PCM audio data from the ADCs. The LM4546B clocks data from this output on the rising edge of BIT_CLK. 11 www.national.com LM4546B Pin Descriptions (Continued) DIGITAL I/O AND CLOCKING (Continued) Name SYNC RESET# ID0 ID1 Pin 10 11 45 46 I/O Functional Description I AC Link frame marker and Warm Reset This input defines the boundaries of AC Link frames. Each frame lasts 256 periods of BIT_CLK. In normal operation SYNC is a 48 kHz positive pulse with a duty cycle of 6.25% (16/256). SYNC is sampled on the falling edge of BIT_CLK and the codec takes the first positive sample of SYNC as defining the start of a new AC Link frame. If a subsequent SYNC pulse occurs within 255 BIT_CLK periods of the frame start it will be ignored. SYNC is also used as an active high input to perform an (asynchronous) Warm Reset. Warm Reset is used to clear a power down state on the codec AC Link interface. I Cold Reset This active low signal causes a hardware reset which returns the control registers and all internal circuits to their default conditions. RESET# MUST be used to initialize the LM4546B after Power On when the supplies have stabilized. Cold Reset also clears the codec from both ATE and Vendor test modes. In addition, while active, it switches the PC_BEEP mono input directly to both channels of the LINE_OUT stereo output. I Codec Identity ID1 and ID0 determine the Codec Identity for multiple codec use. The Codec Identity configures the codec in either Primary or one of three Secondary Codec modes. These Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14) in the read-only Extended Audio ID register, 28h. If the ID0# pin (pin 45) is connected to ground then the ID0 bit (D14, reg 28h) will be set to “1”. Similarly, connection to DVDD will set the ID0 bit to “0”. If left open (NC), ID0# is pulled high by an internal pull-up resistor. I Codec Identity ID1# and ID0# determine the codec address for multiple codec use. The Codec Identity configures the codec in either Primary or one of three Secondary Codec modes. These Identity pins are of inverted polarity relative to the Codec Identity bits ID1, ID0 (bits D15, D14) in the read-only Extended Audio ID register, 28h. If the ID1# pin (pin 46) is connected to ground then the ID1 bit (D15, reg 28h) will be set to “1”. Similarly, connection to DVDD will set the ID1 bit to “0”. If left open (NC), ID1# is pulled high by an internal pull-up resistor. POWER SUPPLIES AND REFERENCES Name Pin I/O AVDD 25 I Functional Description Analog supply AVSS 26 I Analog ground DVDD1 1 I Digital supply DVDD2 9 I Digital supply DVSS1 4 I Digital ground DVSS2 7 I Digital ground VREF 27 O Nominal 2.2 V internal reference Not intended to sink or source current. Use short traces to bypass (3.3 µF, 0.1 µF) this pin to maximize codec performance. See text. VREF_OUT 28 O Nominal 2.2 V reference output Can source up to 5 mA of current and can be used to bias a microphone. 3D SOUND AND NO-CONNECTS (NC) Name 3DP, 3DN www.national.com Pin 33,34 I/O Functional Description O These pins are used to complete the National 3D Sound stereo enhancement circuit. Connect a 0.022 µF capacitor between pins 3DP and 3DN. National 3D Sound can be turned on and off via the 3D bit (D13) in the General Purpose register, 20h. National 3D Sound uses a fixed-depth type stereo enhancement circuit hence the 3D Control register, 22h is read-only and is not programmable. If National 3D Sound is not needed, these pins should be left open (NC). 12 LM4546B Pin Descriptions (Continued) 3D SOUND AND NO-CONNECTS (NC) (Continued) Name Pin I/O NC 14–17 29–32 38–44 47, 48 NC Functional Description These pins are not used and should be left open (NC). For second source applications these pins may be connected to a noise-free supply or ground (e.g. AVDD or AVSS), either directly or through a capacitor. Typical Performance Characteristics ADC Frequency Response DAC Frequency Response 20123319 20123320 ADC Noise Floor DAC Noise Floor 20123315 20123316 Line Out Noise Floor (Analog Loopthrough) 20123318 13 www.national.com 14 X SR15 SR15 Extended Audio 2Ah Control/Status 2Ch PCM DAC Rate 32h PCM ADC Rate X 0 0 74h Vendor Reserved 2 7Ah Vendor Reserved 3 7Ch Vendor ID1 7Eh Vendor ID2 X X X 5Ah Vendor Reserved 1 X ID1 28h Extended Audio ID 26h PR7 X X Powerdown Control/Status 24h Reserved 3D Control 22h (Read Only) X X Mute 18h PCM Out Volume POP Mute 12h CD Volume 20h General Purpose Mute 10h Line In Volume Mute Mute 0Eh Mic Volume 1Ch Record Gain Mute 0Ch Phone Volume X Mute 0Ah PC_Beep Volume 1Ah Record Select Mute 06h Mono Volume X D15 Mute Name 02h Master Volume 00h Reset REG LM4546B Register Map Output Volume Input Volume ADC Sources www.national.com 1 1 X X X SR14 SR14 X ID0 PR6 X 0 X X X X X X X X X X X 0 D14 0 0 X X X SR13 SR13 X X PR5 X 0 3D X X X X X X X X X ML5 0 D13 0 0 X X X SR12 SR12 X X PR4 X 0 X X X GL4 GL4 GL4 X X X X ML4 0 D12 0 1 X X X SR11 SR11 X X PR3 X 0 X GL3 X GL3 GL3 GL3 X X X X ML3 1 D11 0 1 X X X SR10 SR10 X X PR2 X 0 X GL2 SL2 GL2 GL2 GL2 X X X X ML2 1 D10 1 1 X X X SR9 SR9 X 0 PR1 X 0 MIX GL1 SL1 GL1 GL1 GL1 X X X X ML1 0 D9 1 0 X X X SR8 SR8 X 0 PR0 X 1 MS GL0 SL0 GL0 GL0 GL0 X X X X ML0 1 D8 0 0 X X X SR7 SR7 X 0 X X 0 LPBK X X X X X X X X X X 0 D7 1 1 X X X SR6 SR6 X 0 X X 0 X X X X X X 20dB X X X X 1 D6 0 0 X X X SR5 SR5 X X X X 0 X X X X X X X X X MM5 MR5 0 D5 0 1 X X X SR4 SR4 X X X X 0 X X X GR4 GR4 GR4 GN4 GN4 PV3 MM4 MR4 0 D4 0 0 X X X SR3 SR3 X 0 REF X 0 X GR3 X GR3 GR3 GR3 GN3 GN3 PV2 MM3 MR3 0 D3 1 0 X X X SR2 SR2 X X ANL X 0 X GR2 SR2 GR2 GR2 GR2 GN2 GN2 PV1 MM2 MR2 0 D2 1 1 X X X SR1 SR1 X 0 DAC X 0 X GR1 SR1 GR1 GR1 GR1 GN1 GN1 PV0 MM1 MR1 0 D1 0 1 X X X SR0 SR0 VRA VRA ADC X 1 X GR0 SR0 GR0 GR0 GR0 GN0 GN0 X MM0 MR0 0 D0 4346h 4E53h 0000h 0000h 0000h BB80h BB80h 0000h X001h 000Xh 0000h 0101h 0000h 8000h 0000h 8808h 8808h 8808h 8008h 8008h 0000h 8000h 8000h 0D40h Default LM4546B GENERAL fixed depth implementation. The 3D Control register, 22h, is therefore not programmable (read-only). The 3D Sound circuitry defaults to disabled after reset. The LM4546B codec can mix, process and convert among analog (stereo and mono) and digital (AC Link format) inputs and outputs. There are two stereo and four mono analog inputs and one stereo and one mono analog outputs. A single codec supports data streaming on two input and two output channels of the AC Link digital interface simultaneously. ANALOG MIXING: MIX2 MIX2 combines the output of MIX1 (Stereo Mix 3D) with the two mono analog inputs, PHONE and PC_BEEP; each are each level-adjusted by the input control registers, Phone Volume (0Ch) and PC_Beep Volume (0Ah), respectively. If selected by the POP bit (D15, reg 20h), the DAC output is also summed into MIX2. ADC INPUTS AND OUTPUTS Both stereo analog inputs and three of the mono analog inputs can be selected for conversion by the 18-bit stereo ADC. Digital output from the left and right channel ADCs is always located in AC Link Input Frame slots 3 and 4 respectively. Input level to either ADC channel can be muted or adjusted from the Record Gain register, 1Ch. Adjustments are in 1.5 dB steps over a gain range of 0 dB to +22.5 dB and both channels mute together (D15). Input selection for the ADC is through the Record Select Mux controlled from the Record Select register, 1Ah, together with microphone selection controlled by the MS bit (D8) in the General Purpose register, 20h. The stereo input, CD_IN, uses a quasidifferential 3-pin interface where both stereo channel inputs are referenced to the third pin, CD_GND. CD_GND should be AC coupled to the source ground and provides commonmode feedback to cancel ground noise. It is not a DC ground. The other stereo input, LINE_IN, is a 2-pin interface, single-ended for each stereo channel with analog ground (AVSS) as the signals’ reference. Either of the two mono microphone inputs can be muxed to a programmable boost amplifier before selection for either channel of the ADC. The Microphone Mux is controlled by the Microphone Selection (MS) bit (D8) in the General Purpose register 20h and the 20 dB programmable boost is enabled by the 20dB bit (D6) in register 0Eh. The other selectable mono input, coupled directly to the Record Select Mux, is PHONE. STEREO MIX The output of MIX2 is the signal, Stereo Mix. Stereo Mix is used to drive the Line output (LINE_OUT) and can also be selected as the input to the ADC by the Record Select Mux. In addition, the two channels of Stereo Mix are summed to form a mono signal (Mono Mix) also selectable by the Record Select Mux as an input to either channel of the ADC. STEREO OUTPUT The output volume from LINE_OUT can be muted or adjusted by 0 dB to 45 dB in nominal 3 dB steps under the control of the Master Volume register, 02h. As with the input volume registers, adjustments to the levels of the two stereo channels can be made independently but both left and right channels share a mute bit (D15). MONO OUTPUT The mono output (MONO_OUT) is driven by one of two signals selected by the MIX bit (D9) in the General Purpose register, 20h. The signal selected by default (MIX = 0) is the mono summation of the two channels of Stereo Mix 3D, the stereo output of the mixer MIX1. Setting the control bit MIX = 1, selects a microphone input, MIC1 or MIC2. The choice of microphone is controlled by the Microphone Select (MS) bit (D8) also in the General Purpose register, 20h. ANALOG MIXING: MIX1 Three analog inputs are available for mixing at the stereo mixer, MIX1 – both stereo and one mono, namely the microphone input selected by MS (D8, reg 20h). Digital input to the codec can be directed to either MIX1 or to MIX2 after conversion by the 18-bit stereo DAC and level adjustment by the PCM Out Volume control register (18h). Each input to MIX1 may be muted or level adjusted using the appropriate Mixer Input Volume Register: Mic Volume (0Eh), Line_In Volume (10h), CD Volume (12h) and PCM Out Volume (18h). The mono microphone input is mixed equally into left and right stereo channels but stereo mixing is orthogonal, i.e. left channels are only mixed with other left channels and right with right. The left and right amplitudes of any stereo input may be adjusted independently however mute for a stereo input acts on both left and right channels. ANALOG LOOPTHROUGH AND DIGITAL LOOPBACK Analog Loopthrough refers to an all-analog signal path from an analog input through the mixers to an analog output. Digital Loopback refers to a mixed-mode analog and digital signal path from an analog input through the ADC, loopedback (LPBK bit – D7, 20h) through the DAC and mixers to an analog output. This is an 18 bit digital loopback, bypassing the SRC logic, at a 48 kHz rate, even if another sample rate conversion is selected. RESETS COLD RESET is performed when RESET# (pin 11) is pulled low for > 1 µs. It is a complete reset. All registers and internal circuits are reset to their default state. It is the only reset which clears the ATE and Vendor Test Modes. WARM RESET is performed when SYNC (pin 10) is held high for > 1 µs and the codec AC Link digital interface is in powerdown (PR4 = 1, Powerdown Control / Status register, 26h). It is used to clear PR4 and power up the AC Link digital interface but otherwise does not change the contents of any registers nor reset any internal circuitry. REGISTER RESET is performed when any value is written to the RESET register, 00h. It resets all registers to their default state and will modify circuit configurations accordingly but does not reset any other internal circuits. DAC MIXING AND 3D PROCESSING Control of routing the DAC output to MIX1 or MIX2 is by the POP bit (D15) in the General Purpose register, 20h. If MIX1 is selected (default, POP=0) then the DAC output is available for processing by the National 3D Sound circuitry. If MIX2 is selected, the DAC output will bypass the 3D processing. This allows analog inputs to be enhanced by the analog 3D Sound circuitry prior to mixing with digital audio. The digital audio may then use alternative digital 3D enhancements. National 3D Sound circuitry is enabled by the 3D bit (D13) in the General Purpose register, 20h, and is a 15 www.national.com LM4546B Functional Description LM4546B AC Link Serial Interface Protocol 20123304 FIGURE 3. AC Link Bidirectional Audio Frame 20123306 FIGURE 4. AC Link Output Frame AC LINK OUTPUT FRAME: SDATA_OUT, CONTROLLER OUTPUT TO LM4546B INPUT The AC Link Output Frame carries control and PCM data to the LM4546B control registers and stereo DAC. Output Frames are carried on the SDATA_OUT signal which is an output from the AC ’97 Digital Controller and an input to the LM4546B codec. As shown in Figure 3, Output Frames are constructed from thirteen time slots: one Tag Slot followed by twelve Data Slots. Each Frame consists of 256 bits with each of the twelve Data Slots containing 20 bits. Input and Output Frames are aligned to the same SYNC transition. Note that since the LM4546B is a two channel codec, it only accepts data in 4 of the twelve Data Slots – 2 for control, one each for PCM data to the left and right channel DACs. Data Slot 3 & 4 are used to stream data to the stereo DAC for all modes selected by the Identity pins ID1#, ID0#. A new Output Frame is signaled with a low-to-high transition of SYNC. SYNC should be clocked from the controller on a rising edge of BIT_CLK and, as shown in Figure 4 and Figure 5, the first tag bit in the Frame (“Valid Frame”) should be clocked from the controller by the next rising edge of BIT_CLK and sampled by the LM4546B on the following falling edge. The AC ’97 Controller should always clock data www.national.com to SDATA_OUT on a rising edge of BIT_CLK and the LM4546B always samples SDATA_OUT on the next falling edge. SYNC is sampled with the falling edge of BIT_CLK. The LM4546B checks each Frame to ensure 256 bits are received. If a new Frame is detected (a low-to-high transition on SYNC) before 256 bits are received from the old Frame then the new Frame is ignored i.e. the data on SDATA_OUT is discarded until a valid new Frame is detected. The LM4546B expects to receive data MSB first, in an MSB justified format. SDATA_OUT: Slot 0 – Tag Phase The first bit of Slot 0 is designated the "Valid Frame" bit. If this bit is 1, it indicates that the current Output Frame contains at least one slot of valid data and the LM4546B will check further tag bits for valid data in the expected Data Slots. With the codec in Primary mode, a controller will indicate valid data in a slot by setting the associated tag bit equal to 1. Since it is a two channel codec the LM4546B can only receive data from four slots in a given frame and so only 16 Bit Description Comment Codec ID (ID1, ID0) The codec ID is used in a multi-codec system to identify the target Secondary codec for the Control Register address and/or data sent in the Output Frame (Continued) checks the valid-data bits for 4 slots. In Primary mode these tag bits are for: slot 1 (Command Address), slot 2 (Command Data), slot 3 (PCM data for left DAC) and slot 4 (PCM data for right DAC). The last two bits in the Tag contain the Codec ID used to select the target codec to receive the frame in multiple codec systems. When the frame is being sent to a codec in one of the Secondary modes the controller does not use bits 14 and 13 to indicate valid Command Address and Data in slots 1 and 2. Instead, this role is performed by the Codec ID bits – operation of the Extended AC Link assumes that the controller would not access a secondary codec unless it was providing valid Command Address and/or Data. When in one of the secondary modes the LM4546B only checks the tag bits for the Codec ID and for valid data in the two audio data slots 3 & 4. 1,0 SDATA_OUT: Slot 1 – Read/Write, Control Address Slot 1 is used by a controller to indicate both the address of a target register in the LM4546B and whether the access operation is a register read or register write. The MSB of slot 1 (bit 19) is set to 1 to indicate that the current access operation is ’read’. Bits 18 through 12 are used to specify the 7-bit register address of the read or write operation. The least significant twelve bits are reserved and should be stuffed with zeros by the AC ’97 controller. When sending an Output Frame to a Secondary mode codec, a controller should set tag bits 14 and 13 to zero. SLOT 1, OUTPUT FRAME Bits Description 19 Read/Write 18:12 Register Address Identifies the Status/Command register for read/write 11:0 Reserved Controller should set to "0" SLOT 2, OUTPUT FRAME FIGURE 5. Start of AC Link Output Frame Bits SLOT 0, OUTPUT FRAME Description Comment 15 Valid Frame 1 = Valid data in at least one slot. 14 Control register address 1 = Valid Control Address in Slot 1 (Primary codec only) 13 Control register 1 = Valid Control Data in Slot data 2 (Primary codec only) 12 Left DAC data in Slot 3 1 = Valid PCM Data in Slot 3 (Primary & all Secondary modes) 11 Right DAC data in Slot 4 1 = Valid PCM Data in Slot 4 (Primary & all Secondary modes) 10:2 Not Used 1 = Read 0 = Write SDATA_OUT: Slot 2 – Control Data Slot 2 is used to transmit 16-bit control data to the LM4546B when the access operation is ’write’. The least significant four bits should be stuffed with zeros by the AC ’97 controller. If the access operation is a register read, the entire slot, bits 19 through 0 should be stuffed with zeros. 20123305 Bit Comment 19:4 3:0 Description Comment Control Controller should stuff with Register Write zeros if operation is “read” Data Reserved Set to "0" SDATA_OUT: Slots 3 & 4 – PCM Playback Left/Right Channels Slots 3 and 4 are 20-bit fields used to transmit PCM data to the left and right channels of the stereo DAC for all codec Primary and Secondary modes. Any unused bits should be stuffed with zeros. The LM4546B DACs have 18-bit resolution and will therefore use the 18 MSBs of the 20-bit PCM data (MSB justified). SLOTS 3 & 4, OUTPUT FRAME Bits Description Comment Slots used to stream data to PCM DAC Data DACs for all Primary or 19:0 (Left /Right Secondary modes. Channels) Set unused bits to "0" Controller should stuff these slots with “0”s 17 www.national.com LM4546B AC Link Serial Interface Protocol LM4546B AC Link Serial Interface Protocol (Continued) SDATA_OUT: Slots 5 to 12 – Reserved These slots are not used by the LM4546B and should all be stuffed with zeros by the AC ’97 Controller. 20123308 FIGURE 6. AC Link Input Frame AC LINK INPUT FRAME: SDATA_IN, CONTROLLER INPUT FROM LM4546B OUTPUT The AC Link Input Frame contains status and PCM data from the LM4546B control registers and stereo ADC. Input Frames are carried on the SDATA_IN signal which is an input to the AC ’97 Digital Audio Controller and an output from the LM4546B codec. As shown in Figure 3, Input Frames are constructed from thirteen time slots: one Tag Slot followed by twelve Data Slots. The Tag Slot, Slot 0, contains 16 bits of which 5 are used by the LM4546B. One is used to indicate that the AC Link interface is fully operational and the other 4 to indicate the validity of the data in the four of the twelve following Data Slots that are used by the LM4546B. Each Frame consists of 256 bits with each of the twelve data slots containing 20 bits. A new Input Frame is signaled with a low-to-high transition of SYNC. SYNC should be clocked from the controller on a rising edge of BIT_CLK and, as shown in Figure 6 and Figure 7, the first tag bit in the Frame (“Codec Ready”) is clocked from the LM4546B by the next rising edge of BIT_CLK. The LM4546B always clocks data to SDATA_IN on a rising edge of BIT_CLK and the controller is expected to sample SDATA_IN on the next falling edge. The LM4546B samples SYNC on the falling edge of BIT_CLK. Input and Output Frames are aligned to the same SYNC transition. The LM4546B checks each Frame to ensure 256 bits are received. If a new Frame is detected (a low-to-high transition on SYNC) before 256 bits are received from an old Frame then the new Frame is ignored i.e. no valid data is sent on SDATA_IN until a valid new Frame is detected. The LM4546B transmits data MSB first, in a MSB justified format. All reserved bits and slots are stuffed with "0"s by the LM4546B. www.national.com 20123307 FIGURE 7. Start of AC Link Input Frame SDATA_IN: Slot 0 – Codec/Slot Status Bits The first bit (bit 15, “Codec Ready”) of slot 0 in the AC Link Input Frame indicates when the codec’s AC Link digital interface and its status/control registers are fully operational. The digital controller is then able to read the LSBs from the Powerdown Control/Stat register (26h) to determine the status of the four main analog subsections. It is important to check the status of these subsections after Initialization, Cold Reset or the use of the powerdown modes in order to minimize the risk of distorting analog signals passed before the subsections are ready. The 4 bits 14, 13, 12 and 11 indicate that the data in slots 1, 2, 3 and 4, respectively, are valid. 18 SLOT 1, INPUT FRAME (Continued) SLOT 0, INPUT FRAME Bit Description Comment 15 Codec Ready Bit 1 = AC Link Interface Ready 14 Slot 1 data valid 1 = Valid Status Address or Slot Request 13 Slot 2 data valid 1 = Valid Status Data 12 Slot 3 data valid 1 = Valid PCM Data (Left ADC) 11 Slot 4 data valid 1 = Valid PCM Data (Right ADC) Bits Description 19 Reserved 18:12 11 10 SDATA_IN: Slot 1 – Status Address / Slot Request Bits This slot echoes (in bits 18 – 12) the 7-bit address of the codec control/status register received from the controller as part of a read-request in the previous frame. If no readrequest was received, the codec stuffs these bits with zeros. Bits 11, 10 are Slot Request bits that support the Variable Rate Audio (VRA) capabilities of the LM4546B. For all codec Primary and Secondary modes, the left and right channels of the DAC take PCM data from slots 3 and 4 in the Output Frame respectively. The codec will therefore use bits 11 and 10 to request DAC data from these two slots. If bits 11 and 10 are set to 0, the controller should respond with valid PCM data in slots 3 and 4 of the next Output Frame. If bits 11 and 10 are set to 1, the controller should not send data. The codec has full control of the slot request bits. By default, data is requested in every frame, corresponding to a sample rate equal to the frame rate (SYNC frequency) – 48 kHz when XTAL_IN = 24.576 MHz. To send samples at a rate below the frame rate, a controller should set VRA = 1 (bit 0 in the Extended Audio Control/Status register, 2Ah) and program the desired rate into the PCM DAC Rate register, 2Ch. Both DAC channels operate at the same sample rate. Values for common sample rates are given in the Register Description section (Sample Rate Control Registers, 2Ch, 32h) but any rate between 4 kHz and 48 kHz (to a resolution of 1 Hz) is supported. Slot Requests from the LM4546B are issued completely deterministically. For example if a sample rate of 8000 Hz is programmed into 2Ch then the LM4546B will always issue a slot request in every sixth frame. A frequency of 9600 Hz will result in a request every fifth frame while a frequency of 8800 Hz will cause slot requests to be spaced alternately five and six frames apart. This determinism makes it easy to plan task scheduling on a system controller and simplifies application software development. The LM4546B will ignore data in Output Frame slots that do not follow an Input Frame with a Slot Request. For example, if the LM4546B is expecting data at a 8000 Hz rate yet the AC ’97 Digital Audio Controller continues to send data at 48000 Hz, then only those one-in-six audio samples that follow a Slot Request will be used by the DAC. The rest will be discarded. Bits 9 – 2 are request bits for slots not used by the LM4546B and are stuffed with zeros. Bits 1 and 0 are reserved and are also stuffed with zeros. Comment Stuffed with "0" by LM4546B Status Register Echo of the requested Status Index Register address Slot 3 Request bit (For left DAC PCM data) Slot 4 Request bit (For right DAC PCM data) 0 = Controller should send valid data in Slot 3 of the next Output Frame. 1 = Controller should not send Slot 3 data. 0 = Controller should send valid data in Slot 4 of the next Output Frame. 1 = Controller should not send Slot 4 data. 9:2 Unused Slot Request bits Stuffed with "0"s by LM4546B 1,0 Reserved Stuffed with "0"s by LM4546B SDATA_IN: Slot 2 – Status Data This slot returns 16-bit status data read from a codec control/ status register. The codec sends the data in the frame following a read-request by the controller (bit 15, slot 1 of the Output Frame). If no read-request was made in the previous frame the codec will stuff this slot with zeros. SLOT 2, INPUT FRAME Bits Description Comment 19:4 Status Data Data read from a codec control/status register. Stuffed with “0”s if no read-request in previous frame. 3:0 Reserved Stuffed with "0"s by LM4546B SDATA_IN: Slot 3 – PCM Record Left Channel This slot contains sampled data from the left channel of the stereo ADC. The signal to be digitized is selected using the Record Select register (1Ah) and subsequently routed through the Record Select Mux and the Record Gain amplifier to the ADC. This is a 20-bit slot and the digitized 18-bit PCM data is transmitted in an MSB justified format. The remaining 2 LSBs are stuffed with zeros. SLOT 3, INPUT FRAME 19 Bits Description 19:2 PCM Record Left Channel data 1:0 Reserved Comment 18-bit PCM sample from left ADC Stuffed with "0"s by LM4546B www.national.com LM4546B AC Link Serial Interface Protocol LM4546B AC Link Serial Interface Protocol SLOT 4, INPUT FRAME (Continued) Bits SDATA_IN: Slot 4 – PCM Record Right Channel 19:2 This slot contains sampled data from the right channel of the stereo ADC. The signal to be digitized is selected using the Record Select register (1Ah) and subsequently routed through the Record Select Mux and the Record Gain amplifier to the ADC. This is a 20-bit slot and the digitized 18-bit PCM data is transmitted in an MSB justified format. The remaining 2 LSBs are stuffed with zeros. www.national.com 1:0 Description Comment PCM Record 18-bit PCM audio sample from Right Channel right ADC data Reserved Stuffed with "0"s by LM4546B SDATA_IN: Slots 5 to 12 – Reserved Slots 5 – 12 of the AC Link Input Frame are not used for data by the LM4546B and are always stuffed with zeros. 20 Default settings are indicated by *. Mute PV3:PV0 RESET REGISTER (00h) 0 0000 *0 dB attenuation Writing any value to this register causes a Register Reset which changes all registers back to their default values. If a read is performed on this register, the LM4546B will return a value of 0D40h. This value can be interpreted in accordance with the AC ’97 specification to indicate that National 3D Sound is implemented and 18-bit data is supported for both the ADCs and DACs. 0 1111 45 dB attenuation 1 XXXX Mx5:Mx0 0 0 00000 0 dB attenuation 0 0 11111 46.5 dB attenuation 0 1 xxxxx As written 0 0 11111 As read back 1 X XXXXX mute Default: 0000h MIXER INPUT VOLUME REGISTERS (Index 0Ch - 18h) These input registers adjust the volume levels into the stereo mixers MIX1 and MIX2. Each channel may be adjusted over a range of +12 dB gain to –34.5 dB attenuation in 1.5 dB steps. For stereo ports, volumes of the left and right channels can be independently adjusted. Muting a given port is accomplished by setting the MSB to 1. Setting the MSB to 1 for stereo ports mutes both the left and right channel. The Mic Volume register (0Eh) controls an additional 20 dB boost for the selected microphone input by setting the 20dB bit (D6). MASTER VOLUME REGISTER (02h) This output register allows the output level from either channel of the stereo LINE_OUT to be muted or attenuated over the range 0 dB – 46.5 dB in nominal 1.5 dB steps. There are 6 bits of volume control for each channel and both stereo channels can be individually attenuated. The mute bit (D15) acts simultaneously on both stereo channels of LINE_OUT. The AC’97 specification states that “support for the MSB of the level is optional.” All six bits may be written to the register, but if the MSB is a 1, the MSB is ignored and the register will be set to 0 11111. This will be the value when the register is read, allowing the software driver to detect whether the MSB is supported or not. Mute Function Function Mute Gx4:Gx0 0 0 0000 +12 dB gain 0 0 1000 0 dB gain 0 1 1111 1 X XXXX Default: Function 34.5 dB attenuation *mute 8008h (mono registers) 8808h (stereo registers) RECORD SELECT REGISTER (1Ah) This register independently controls the sources for the right and left channels of the stereo ADC. The default value of 0000h corresponds to selecting the (mono) Mic input for both channels. *mute Default: 8000h MONO VOLUME REGISTER (06h) This output register allows the level from MONO_OUT to be muted or attenuated over the range 0 dB – 46.5 dB in nominal 1.5 dB steps. There are 6bits of volume control and one mute bit (D15). All six bits may be written to the register, but if the MSB is a 1, the MSB is ignored and the register will be set to 0 11111. This will be the value when the register is read, allowing the software driver to detect whether the MSB is supported or not. SL2:SL0 Function Source for Left Channel ADC 0 *Mic input 1 CD input (L) 2 Not used 3 Not used 4 LINE_IN input (L) 5 Stereo Mix (L) 6 Mono Mix 7 PHONE input Mute MM5:MM0 0 0 00000 0 dB attenuation 0 0 11111 46.5 dB attenuation 0 1 xxxxx As written 0 *Mic input 0 0 11111 As read back 1 CD input (R) 1 X XXXXX *mute 2 Not used 3 Not used 4 LINE_IN input (R) 5 Stereo Mix (R) 6 Mono Mix 7 PHONE input SR2:SR0 Default: 8000h PC BEEP VOLUME REGISTER (0Ah) This input register adjusts the level of the mono PC_BEEP input to the stereo mixer MIX2 where it is summed equally into both channels of the Stereo Mix signal. PC_BEEP can be both muted and attenuated over a range of 0 dB to 45 dB in nominal 3 dB steps. Note that the default setting for the PC_Beep Volume register is 0 dB attenuation rather than mute. Source for Right Channel ADC Default: 0000h 21 www.national.com LM4546B Register Descriptions LM4546B Register Descriptions status information can be transferred. It does NOT indicate that the codec is ready to send or receive audio PCM data or to pass signals through the analog I/O and mixers. To determine that readiness, the Controller must check that the 4 LSBs of this register are set to “1” indicating that the appropriate audio subsections are ready. (Continued) RECORD GAIN REGISTER (1Ch) This register controls the input levels for both channels of the stereo ADC. The inputs come from the Record Select Mux and are selected via the Record Select Control register, 1Ah. The gain of each channel can be individually programmed from 0 dB to +22.5 dB in 1.5 dB steps. Both channels can also be muted by setting the MSB to 1. The powerdown bits PR0 – PR5 control internal subsections of the codec. They are implemented in compliance with AC ’97 Rev 2.1 to support the standard device power management states D0 – D3 as defined in the ACPI and PCI Bus Power Management specification. Record Gain Register (1Ch) Mute Gx3:Gx0 PR0 controls the powerdown state of the ADC and associated sampling rate conversion circuitry. PR1 controls powerdown for the DAC and the DAC sampling rate conversion circuitry. PR2 powers down the mixer circuits (MIX1, MIX2, National 3D Sound, Mono Out, Line Out). PR3 powers down VREF in addition to all the same mixer circuits as PR2. PR4 powers down the AC Link digital interface – see Figure 8 for signal powerdown timing. PR5 disables internal clocks. PR6 and PR7 are not used. Function 0 1111 +22.5 dB gain 0 0000 0 dB gain 1 XXXX *mute Default: 8000h GENERAL PURPOSE REGISTER (20h) BIT# This register controls many miscellaneous functions implemented on the LM4546B. The miscellaneous control bits include POP which allows the DAC output to bypass the National 3D Sound circuitry, 3D which enables or disables the National 3D Sound circuitry, MIX which selects the MONO_OUT source, MS which controls the Microphone Selection mux, and LPBK which connects the 18 bit output of the stereo ADC to the 18 bit input of the stereo DAC, bypassing the Sample Rate Conversion (SRC) logic. LPBK provides a mixed-mode analog and digital loopback path between analog inputs and analog outputs. BIT POP 3D MIX MS LPBK Function PCM Out Path: *0 = 3D allowed 1 = 3D bypassed National 3D Sound: Mic select: *0 = No Loopback 1 = Loopback 1 DAC 1 = DAC section ready to accept data 2 ANL 1 = Analog mixers ready 3 REF 1 = VREF is up to nominal level BIT# BIT Function: Powerdown 8 PR0 1 = Powerdown ADCs and Record Select Mux 9 PR1 1 = Powerdown DACs 10 PR2 1 = Powerdown Analog Mixer (VREF still on) 11 PR3 1 = Powerdown Analog Mixer (VREF off) 12 PR4 1 = Powerdown AC Link digital interface (BIT_CLK off) 13 PR5 1 = Disable Internal Clock 14 PR6 Not Used 15 PR7 Not Used Default: 000Fh If ready; otherwise 000Xh (see text) Default: 0000h EXTENDED AUDIO ID REGISTER (28h) This read-only register (X001h) identifies which AC ’97 Extended Audio features are supported. The LM4546B features VRA (Variable Rate Audio) and ID1, ID0 (Multiple Codec support). VRA is indicated by a "1" in bit 0. The two MSBs, ID1 and ID0, show the current Codec Identity as defined by the Identity pins ID1#, ID0# (pins 46 and 45). Note that the external logic connections to ID1#, ID0#, are inverse in polarity to the value of the Codec Identity (ID1, ID0) held in bits D15, D14. Codec mode selections are shown in the table below. 3D CONTROL REGISTER (22h) This read-only (0101h) register indicates, in accordance with the AC ’97 Rev 2.1 Specification, the fixed depth and center characteristics of the National 3D Sound stereo enhancement. POWERDOWN CONTROL / STATUS REGISTER (26h) This read/write register is used both to monitor subsystem readiness and also to program the LM4546B powerdown states. The 4 LSBs indicate status and 6 of the 8 MSBs control powerdown. The 4 LSBs of this register indicate the status of the 4 audio subsections of the codec: Reference voltage, Analog mixers and amplifiers, DAC section, ADC section. When the "Codec Ready" indicator bit in the AC Link Input Frame (SDATA_IN: slot 0, bit 15) is a "1", it indicates that the AC Link and AC ’97 registers are in a fully operational state and that control and www.national.com ADC *0 = MIC1 1 = MIC2 ADC/DAC Loopback: 0 *0 = Mix 1 = Mic Function: Status 1 = ADC section ready to transmit data *0 = off 1 = on Mono output select: BIT Pin 46 (ID1) 22 Pin 45 (ID0) D15,28h D14,28h Codec Identity (ID1) (ID0) Mode NC/DVDD NC/DVDD 0 0 Primary NC/DVDD 0 1 Secondary 1 GND RESERVED REGISTERS Do not write to reserved registers. In particular, do not write to registers 24h, 5Ah, 74h and 7Ah. All registers not listed in the LM4546B Register Map are reserved. Reserved Registers will return 0000h if read. (Continued) Pin 46 (ID1) Pin 45 (ID0) D15,28h D14,28h Codec Identity (ID1) (ID0) Mode GND NC/DVDD 1 0 Secondary 2 GND GND 1 1 Secondary 3 Low Power Modes EXTENDED AUDIO STATUS/CONTROL REGISTER (2Ah) This read/write register provides status and control of the variable sample rate capabilities in the LM4546B. Setting the LSB of this register to "1" enables Variable Rate Audio (VRA) mode and allows DAC and ADC sample rates to be programmed via registers 2Ch and 32h respectively. BIT VRA The LM4546B provides 6 bits to control the powerdown state of internal analog and digital subsections and clocks. These 6 bits (PR0 – PR5) are located in the 8 MSBs of the Powerdown Control/Status register, 26h. The status of the four main analog subsections is given by the 4 LSBs in the same register, 26h. The powerdown bits are implemented in compliance with AC ’97 Rev 2.1 to support the standard device power management states D0 – D3 as defined in the ACPI and PCI Bus Power Management specification. Function *0 = VRA off (Frame-rate sampling) 1 = VRA on PR0 controls the powerdown state of the ADC and associated sampling rate conversion circuitry. PR1 controls powerdown for the DAC and the DAC sampling rate conversion circuitry. PR2 powers down the mixer circuits (MIX1, MIX2, National 3D Sound, Mono Out, Line Out). PR3 powers down VREF in addition to all the same mixer circuits as PR2. PR4 powers down the AC Link Digital Interface – see Figure 8 for signal powerdown timing. PR5 disables internal clocks but leaves the crystal oscillator and BIT_CLK running (needed for minimum Primary mode powerdown dissipation in multicodec systems). PR6 and PR7 are not used. After a subsection has undergone a powerdown cycle, the appropriate status bit(s) in the Powerdown Control/Status register (26h) must be polled to confirm readiness. In particular the startup time of the VREF circuitry depends on the value of the decoupling capacitors on pin 27 (3.3 µF, 0.1 µF in parallel is recommended) and this dependency is behind the requirement for both PR2 and PR3 functionality in AC ’97 Rev 2.1. When the AC Link Digital Interface is powered down the codec output signals SDATA_IN and BIT_CLK (Primary mode) are cleared to zero and no control data can be passed between controller and codec(s). This powerdown state can be cleared in two ways: Cold Reset (RESET# = 0) or Warm Reset (SYNC = 1, no BIT_CLK). Cold Reset sets all registers back to their default values (including clearing PR4) whereas Warm Reset only clears the PR4 bit and restarts the AC Link Digital Interface leaving all register contents otherwise unaffected. For Warm Reset (see Timing Diagrams), the SYNC input is used asynchronously. The LM4546B codec allows the AC Link digital interface powerdown state to be cleared immediately so that its duration can be essentially as short as TSH, the Warm Reset pulse width. However for conformance with AC ’97 Rev 2.1, Warm Reset should not be applied within 4 frame times of powerdown i.e. the AC Link powerdown state should be allowed to last at least 82.8 µs. Default: 0000h SAMPLE RATE CONTROL REGISTERS (2Ch, 32h) These read/write registers are used to set the sample rate for the left and right channels of the DAC (PCM DAC Rate, 2Ch) and the ADC (PCM ADC Rate, 32h). When Variable Rate Audio is enabled via bit 0 of the Extended Audio Control/Status register (2Ah), the sample rates can be programmed, in 1 Hz increments, to be any value from 4 kHz to 48 kHz. The value required is the hexadecimal representation of the desired sample rate, e.g. 800010 = 1F40h. Below is a list of the most common sample rates and the corresponding register (hex) values. Common Sample Rates SR15:SR0 Sample Rate (Hz) 1F40h 8000 2B11h 11025 3E80h 16000 5622h 22050 AC44h 44100 *BB80h *48000 VENDOR ID REGISTERS (7Ch – 7Eh) These two read-only (4E53h, 4346h) registers contain National’s Vendor ID and National’s LM45xx codec version designation. The first 24 bits (4Eh, 53h, 43h) represent the three ASCII characters “NSC” which is National’s Vendor ID for Microsoft’s Plug and Play. The last 8 bits are the two binary coded decimal characters, 4, 6 and identify the codec to be an LM4546B. 23 www.national.com LM4546B Register Descriptions LM4546B Low Power Modes (Continued) 20123309 FIGURE 8. AC Link Powerdown Timing dB point will still be below 300 Hz. By using a smaller capacitor, the package size may be reduced, leading to a lower system cost. Improving System Performance The audio codec is capable of dynamic range performance in excess of 90 db., but the user must pay careful attention to several factors to achieve this. A primary consideration is keeping analog and digital grounds separate, and connecting them together in only one place. Some designers show the connection as a zero ohm resistor, which allows naming the nets separately. Although it is possible to use a two layer board, it is recommended that a minimum of four layers be used, with the two inside layers being analog ground and digital ground. If EMI is a system consideration, then as many as eight layers have been successfully used. The 12 and 25 MHz. clocks can have significant harmonic content depending on the rise and fall times. With the exception of the digital VDD pins, (covered later) bypass capacitors should be very close to the package. The analog VDD pins should be supplied from a separate regulator to reduce noise. By operating the digital portion on 3.3V instead of 5V, an additional 0.5-0.7 db improvement can be obtained. The bandgap reference and the anti-pop slow turn-on circuit were improved in the LM4546B. A pullup resistor is not required on VREF, pin 27. For an existing design, the 10 kΩ resistor can be left on the pc board, but the temperature coefficient will improve with no resistor on this pin. In addition, the THD will improve by 0.2–0.5 dB. The external capacitor is charged by an internal current source, ramping the voltage slowly. This results in slow turn-on of the audio stages, eliminating “pops and clicks”. Thus, turn-on performance is also improved. The pullup resistor, in conjunction with the internal impedance and the external capacitor, form a frequency dependent divider from the analog supply. Noise on the analog supply will be coupled into the audio path, with approximately 30 dB.of attenuation. Although this is not a large amount if the noise on the supply is tens of millivolts, it will prevent SNR from exceeding 80 dB. In Figure 1 and Figure 2, the input coupling capacitors are shown as 1 µF. capacitors. This is only necessary for extending the response down to 20 Hz. for music applications. For telematics or voice applications, the lower 3 dB. can be much higher. Using a guaranteed input resistance of 10 kΩ, (40 kΩ typical), a 0.1 µF capacitor may be used. The lower 3 www.national.com Backwards Compatibility The LM4546B is improved compared to the LM4546A. If it is required to build a board that will use either part, a 10 kΩ resistor must be added from the VREF pin (pin 27) to AVDD for the LM4546A. It is not required for the LM4546B. Addition of this resistor will slightly increase the temperature coefficient of the internal bandgap reference and slightly decrease the THD performance, but overall performance will still be better than the LM4546A. The LM4546A requires that pins 1 and 9 (DVDD) connect directly to a 27 nH. inductor before going to the 3.3 Volt digital supply and bypass capacitors. The inductor is not required for the LM4546B and should not be used. Multiple Codecs EXTENDED AC LINK Up to four codecs can be supported on the extended AC Link. These multiple codec implementations should run off a common BIT_CLK generated by the Primary Codec. All codecs share the AC ’97 Digital Controller output signals, SYNC, SDATA_OUT, and RESET#. Each codec, however, supplies its own SDATA_IN signal back to the controller, with the result that the controller requires one dedicated input pin per codec (Figure 9). By definition there can be one Primary Codec and up to three Secondary Codecs on an extended AC Link. The Primary Codec has a Codec Identity = (ID1, ID0) = ID = 00 while Secondary Codecs take identities equal to 01, 10 or 11. The Codec Identity is used as a chip select function. This allows the Command and Status registers in any of the codecs to be individually addressed although the access mechanism for Secondary Codecs differs slightly from that for a Primary. 24 the Command Address in slot 1 and (if a “write”) the Command Data in slot 2 are valid. When reading from a Secondary Codec, the controller must send the correct Codec ID bits (i.e. the target Codec Identity in slot 0, bits 1 and 0) along with the read-request bit (slot 1, bit 19) and target register address (slot 1, bits 18 – 12). To write to a Secondary Codec, a controller must send the correct Codec ID bits when slot 1 contains a valid target register address and “write” indicator bit and slot 2 contains valid target register data. A write operation is only valid if the register address and data are both valid and sent within the same frame. When accessing the Primary Codec, the Codec ID bits are cleared and the tag bits 14 and 13 resume their role indicating the validity of Command Address and Data in slots 1 and 2. The use of the tag bits in Input Frames (carried by the SDATA_IN signal) is the same for Primary and Secondary Codecs. (Continued) The Identity control pins, ID1, ID0 (pins 46 and 45) are internally pulled up to DVDD. The Codec may therefore be configured as ’Primary’ either by leaving ID1, ID0 open (NC) or by strapping them externally to DVDD (Digital supply). The difference between Primary and Secondary codec modes is in their timing source and in the Tag Bit handling in Output Frames for Command/Status register access. For a timing source, a Primary codec divides down by 2 the frequency of the signal on XTAL_IN and also generates this as the BIT_CLK output for the use of the controller and any Secondary codecs. Secondary codecs use BIT_CLK as an input and as their timing source and do not use XTAL_IN or XTAL_OUT. The use of Tag Bits is described below. SECONDARY CODEC REGISTER ACCESS For Secondary Codec access, the controller must set the tag bits for Command Address and Data in the Output Frame as invalid (i.e. equal to 0). The Command Address and Data tag bits are in slot 0, bits 14 and 13 and Output Frames are those in the SDATA_OUT signal from controller to codec. The controller must also place the non-zero value (01, 10, or 11) corresponding to the Identity (ID1, ID0) of the target Secondary Codec into the Codec ID field (slot 0, bits 1 and 0) in that same Output Frame. The value set in the Codec ID field determines which of the three possible Secondary Codecs is accessed. Unlike a Primary Codec, a Secondary Codec will disregard the Command Address and Data tag bits when there is a match between the 2-bit Codec ID value (slot 0, bits 1 and 0) and the Codec Identity (ID1, ID0). Instead it uses the Codec-ID/Identity match to indicate that The Codec Identity is determined by the input pins ID1#, ID0# (pins 46 and 45) and can be read as the value of the ID1, ID0 bits (D15, D14) in the Extended Audio ID register, 28h of the target codec. Slots in the AC Link Output Frame are always mapped to carry data to the left DAC channel in slot 3 and data to the right DAC channel in slot 4. Similarly, slots in AC Link Input Frames are always mapped such that PCM data from the left ADC channel is carried by slot 3 and PCM data from the right ADC channel by slot 4. Output Frames are those carried by the SDATA_OUT signal from the controller to the codec while Input Frames are those carried by the SDATA_IN signal from the codec to the controller. SLOT 0: TAG bits in Output Frames (controller to codec) Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 X X X X X X X X X ID1 ID0 Valid Slot 1 Slot 2 Slot 3 Slot 4 Frame Valid Valid Valid Valid Extended Audio ID register (28h): Support for Multiple Codecs Reg Name 28h Extended Audio ID D15 D14 D13 D12 D11 D10 ID1 ID0 X X X X D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Default X X X X X X X X X VRA X001h 25 www.national.com LM4546B Multiple Codecs LM4546B Multiple Codecs (Continued) 20123323 FIGURE 9. Multiple Codecs using Extended AC Link for controller testing. ATE test mode timing parameters are given in the Electrical Characteristics table. The Vendor test mode is entered if SYNC is sampled high by the zero-to-one transition of RESET#. Neither of these entry conditions can occur in normal AC Link operation but care must be taken to avoid mistaken activation of the test modes when using non standard controllers. Test Modes AC ’97 Rev 2.1 defines two test modes: ATE test mode and Vendor test mode. Cold Reset is the only way to exit either of them. The ATE test mode is activated if SDATA_OUT is sampled high by the trailing edge (zero-to-one transition) of RESET#. In ATE test mode the codec AC Link outputs SDATA_IN and BIT_CLK are then configured to a high impedance state to allow tester control of the AC Link interface www.national.com 26 inches (millimeters) unless otherwise noted 48-Lead , LQFP, 7 X 7 X 1.4mm, JEDEC (M) Order Number LM4546BVH NS Package Number VBH48A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. 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