Digital BTSC Encoder with Integrated ADC and DAC AD1970 APPLICATIONS FEATURES Digital set top box DVD player DVD recorder Complete BTSC encoder Pilot tone generator Includes subcarrier modulation Channel separation: 30 dB Bandwidth up to 14 kHz Stereo analog or digital input Phat-Stereo™ algorithm for stereo image enhancement Dialog enhancement function for playing wide dynamic range video sources over built-in TV speakers Includes L − R dual-band compressor I2C port for control of modes, effects, and parameters Analog input performance 74 dB dynamic range −72 dB THD + N Digital input performance 87 dB dynamic range −83 dB THD + N Integrated op amps for analog inputs and outputs Single-ended output reduces external part count Integrated PLL generates all clocks from composite video, 48 kHz sample clock, or high speed master clock Sync stripper to recover video clock from composite video signal Output level control for setting aural carrier deviation GENERAL DESCRIPTION The AD1970 is a complete analog or digital-in, analog-out BTSC encoder which includes pilot-tone generation and subcarrier mixing functions. The stereo ADC provides the means for digitization of the analog baseband audio signal. A built-in high performance DAC is provided to output the BTSC baseband composite signal. The output of the AD1970 can be connected with minimal external circuitry to the input of a 4.5 MHz aural FM modulator. In addition to the digital BTSC encoder, the AD1970 includes a stereo image enhancement function, Phat Stereo, to increase the sense of spaciousness available from closely spaced TV loudspeakers. A dialog enhancement algorithm solves the problem of playing wide dynamic range sources over limitedperformance TV speakers and amplifiers. An I2C port allows control of the AD1970’s registers and parameters. The AD1970 utilizes ADI’s patented multibit Σ-Δ architecture to provide BTSC performance of up to 87 dB dynamic range and a THD+N of −83 dB. Macrovision™-compliant The AD1970 includes patented BTSC stereo TV technology licensed from THAT Corporation. Dolby™ RF mode-compatible 48-pin LQFP plastic package FUNCTIONAL BLOCK DIAGRAM AD1970 ADC DECIMATION FILTER ADC DIGITAL AUDIO INTERFACE SYNC STRIPPER COMPOSITE VIDEO I2C I/O GROUP BTSC ENCODER CORE 3 4 PLL BTSC ENCODED OUTPUT CONTROL REGISTERS I2C PORT ADC VOLUME CONTROL DAC ANALOG BIAS 05500-001 ANALOG L/R INPUTS Figure 1. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. www.analog.com Tel: 781.329.4700 Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved. AD1970 TABLE OF CONTENTS Specifications..................................................................................... 3 Power-Up Sequence ................................................................... 11 Absolute Maximum Ratings............................................................ 6 Control Port .................................................................................... 12 Package Characteristics (48-Lead LQFP).................................. 6 I2C Port Overview ...................................................................... 12 ESD Caution.................................................................................. 6 I2C Address Decoding................................................................ 12 Pin Configuration and Function Descriptions............................. 7 Input Level Control.................................................................... 13 Theory of Operation ........................................................................ 9 Output Level Control................................................................. 13 Signal Processing ............................................................................ 10 I2C Read/Write Data Formats................................................... 14 Background of BTSC ................................................................. 10 Analog Input/Output ..................................................................... 16 Performance Factors .................................................................. 10 ADC Input................................................................................... 16 Separation Alignment ................................................................ 11 DAC Output................................................................................ 16 Phase Linearity of the External Analog Filter......................... 11 Serial Data Port........................................................................... 16 Input Levels ................................................................................. 11 Serial Data Modes ...................................................................... 16 Clocking and PLL....................................................................... 11 Typical Applications Circuit.......................................................... 18 Crystal Oscillator........................................................................ 11 Outline Dimensions ....................................................................... 19 General Purpose Input/Output (GPIO) Pins ......................... 11 Ordering Guide .......................................................................... 19 REVISION HISTORY 4/05—Revision 0: Initial Version Rev. 0 | Page 2 of 20 AD1970 SPECIFICATIONS Test conditions, unless otherwise noted Table 1. Parameters Supply Voltages (AVDD, DVDD) Ambient Temperature Input Signal Input Sample Rate Measurement Bandwidth Word Width Load Capacitance Load Current Input Voltage High Input Voltage Low Conditions 3.3 25 1 kHz, 0.8 VRMS analog, 0 dBFS digital 48 20 Hz to 14 kHz 24 50 ±1 2.0 0.8 Unit V °C Hz, V rms, dBFS kHz kHz Bits pF mA V V Table 2. Analog Input Performance Parameter Maximum Input Level Output Level Dynamic Range (20 Hz to 14 kHz, –60 dB Input) (Encoded Output, Left = Right) THD + Noise (Encoded Output, Left = Right, 20 Hz to 14 kHz) VIN = 0 dBV rms Min Typ 1.0 (2.8) 250 74 Max Unit V rms (V p-p) mV rms dB –72 –65 dB Typ 24 250 87 Max Unit Bits mV rms dB –83 –74 dB Min 0.35 Typ 1.0 2 Max Unit VP-P kΩ Min 7 Typ 10 Max 13 Unit mmhos 68 Table 3. Digital Input Performance Parameter Resolution Output Level Dynamic Range (20 Hz to 14 kHz, –60 dB Input) (Encoded Output, Left = Right) THD + Noise (Encoded Output, Left = Right, 20 Hz to 14 kHz) VIN = 0 dBFS Min 81 Table 4. Video Input Parameter Input Signal Level Input Impedance Table 5. Crystal Oscillator Parameter Transconductance Rev. 0 | Page 3 of 20 AD1970 Table 6. BTSC Encoder Performance Parameter CHANNEL SEPARATION (–25 dB INPUT) 30 Hz to 500 Hz 500 Hz to 5 kHz 5 kHz to 13.5 kHz CHANNEL SEPARATION AT 1 kHz 0 dB Input –2 dB Input FREQUENCY RESPONSE 30 Hz to 10 kHz 30 Hz to 13.5 kHz Min Typ 24 18 14 30 21 15 25 24 27 26 –1 –1.5 Max Unit dB dB dB +0.5 +0.5 dB dB Table 7. Digital I/O Parameter Input Voltage High (VIH) Input Voltage Low (VIL) Input Leakage (IIH @ VIH = 2.4 V) Input Leakage (IIL @ VIL = 0.4 V) High Level Output Voltage (VOH) IOH = 2 mA (except VID_PRES) Low Level Output Voltage (VOL) IOL = 2 mA Min 2.0 Typ Max 0.4 Unit V V µA µA V V 0.8 10 10 DVDD − 0.6 Table 8. Power Parameter SUPPLIES Voltage, Analog, Digital, PLL Analog Current Digital Current PLL Current DISSIPATION All Supplies Analog Supply Digital Supply PLL Supply Min Typ Max Unit 3.0 30 30 1 3.3 41 38 5 3.6 50 48 8 V mA mA mA 277 135 125 17 mW mW mW mW Table 9. Temperature Range Parameter Specifications Guaranteed Functionality Guaranteed Storage Min 0 –55 Rev. 0 | Page 4 of 20 Typ 25 Max 70 +125 Unit °C °C °C AD1970 Table 10. Digital Timing Parameter tDMD tDBL tDBH tDBL tDBH tDLS tDLH tDDS tDDH tIBC tISST tIH tSDS tSDH tSDF tSDR tPWS tPDRP MCLK Duty Cycle, External 512 fS Mode MCLK Low Pulse Width, External 512 fS Mode MCLK High Pulse Width, External 512 fS Mode MCLK Low Pulse Width, PLL, 256 fS or fS Mode MCLK High Pulse Width, PLL, 256 fS or fS Mode LRCLK Setup LRCLK Hold SDATA Setup SDATA Hold I2C Bus Clock Frequency I2C Setup Time for Start Condition I2C Hold Time for Start Condition SDA Setup Time SDA Hold Time SDA Fall Time at 3 mA Sink and 400 pF Load SDA Rise Time Pulse Width of Spikes Supressed by the Input Filter RESETB Low Pulse Width Rev. 0 | Page 5 of 20 Min 40 15 15 15 15 10 10 10 10 Typ 50 Max 60 400 10 30 50 25 25 300 50 15 Unit % ns ns ns ns ns ns ns ns kHz ns ns ns ns ns ns ns ns AD1970 ABSOLUTE MAXIMUM RATINGS Table 11. DVDD to DGND ODVDD to DGND AVDD to AGND Digital Inputs Analog Inputs AGND to DGND Reference Voltage Maximum Junction Temperature Storage Temperature Range Min –0.3 –0.3 –0.3 DGND – 0.3 AGND – 0.3 –0.3 Max +3.95 +3.95 +3.95 DVDD + 0.3 AVDD + 0.3 +0.3 (AVDD + 0.3)/2 Unit V V V V V V V +125 +150 °C °C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. PACKAGE CHARACTERISTICS (48-LEAD LQFP) Table 12. –65 Min θJA (Thermal Resistance [Junction-to-Ambient]) θJC (Thermal Resistance [Junction-to-Case]) ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. 0 | Page 6 of 20 Typ 72 19.5 Max Unit °C/W °C/W AD1970 48 47 46 45 44 43 42 41 40 39 DVDD GPIO2 GPIO3 SDATA BCLK LRCLK DIG_IN_EN SDA SCL ADR1 ADR0 DGND PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 38 37 DVDD 1 36 DGND RESETB 2 35 GPIO1 DGND 3 34 GPIO0 DVDD 4 33 XIN RSVD 5 32 XOUT 31 VID_PRES 30 MCLK AVDD 8 29 PLL_MODE1 BTSC_OUT 9 28 PLL_MODE0 AGND 10 27 NC VREF 11 26 VID_IN FILTCAP 12 25 PGND AD1970 NC = NO CONNECT PLL_LF PVDD CAPRN CAPLN CAPRP 20 21 22 23 24 CAPLP 17 18 19 VIN_IAMPR AVDD VIN_IAMPL 14 15 16 VOUT_IAMPL 13 AGND VIN_OAMP 7 VOUT_IAMPR TOP VIEW (Not to Scale) 05500-002 VOUT_OAMP 6 Figure 2. Pin Configuration Table 13. Pin Function Descriptions Pin No. 1 2 Pin Name DVDD RESETB Input/Output 3 4 5 6 7 8 9 DGND DVDD RSVD VOUT_OAMP VIN_OAMP AVDD BTSC_OUT 10 11 AGND VREF OUT 12 FILTCAP OUT 13 AVDD 14 15 16 17 AGND VOUT_IAMPL VIN_IAMPL VOUT_IAMPR IN OUT IN OUT OUT IN OUT Description Digital Power. Reset—Active Low. After RESETB transitions from low to high, the AD1970 BTSC encoder core goes through an initialization sequence where all registers are set to 0. The initialization is completed after 1024 MCLK cycles. New values should not be written to the control port until the initialization is complete. Digital Ground. Digital Power. 3.3 V nominal. Reserved—Connect to DGND. Output voltage of internal op amp to be used for BTSC output low pass filter. Negative input of internal op amp to be used for BTSC output low pass filter. Analog Power. Encoded BTSC Output. The nominal output voltage for a 300 Hz, 0 dB mono input signal is 250 mV rms. Analog Ground. Connection for voltage reference noise reduction capacitor. The nominal VREF voltage is 1.5 V; the analog gain scales directly with the voltage on this pin. Any ac signal on this pin causes distortion and therefore a large decoupling capacitor should be used to ensure the voltage on VREF is clean. Connection for DAC noise reduction capacitor. A 10 µF capacitor should be connected to this pin to reduce the noise on an internal DAC biasing point to provide the highest performance. It may not be necessary to connect this pin, depending on the quality of the layout and grounding used in the application circuit. Analog Power. 3.3 V nominal. Bypass capacitors should be placed close to the pins and connected directly to the analog ground plane. Analog Ground. Output of internal op amp for left channel input amplifier. Negative input of internal op amp for left channel input amplifier. Output of internal op amp for right channel input amplifier. Rev. 0 | Page 7 of 20 AD1970 Pin No. 18 19 Pin Name VIN_IAMPR CAPLP Input/Output IN I/O 20 CAPLN I/O 21 CAPRP I/O 22 CAPRN I/O 23 PVDD 24 25 26 PLL_LF PGND VID_IN IN 27 28 NC PLL_MODE0 IN 29 PLL_MODE1 IN 30 MCLK IN 31 VID_PRES OUT 32 XOUT OUT 33 XIN IN 34 GPIO0 IN/OUT 35 GPIO1 IN/OUT 36 37 38 DGND DVDD GPIO2 IN/OUT 39 GPIO3 IN/OUT 40 SDATA IN/OUT 41 BCLK IN/OUT 42 LRCLK IN/OUT 43 44 45 46 47 48 DIG_IN_EN SDA SCL ADR1 ADR0 DGND IN IN/OUT IN IN IN Description Negative input of internal op amp for right channel input amplifier. ADC Filter Capacitor Connection (positive left-channel input to modulator). A 1 nF capacitor should be placed between this pin and analog ground. ADC Filter Capacitor Connection (negative left-channel input to modulator). A 1 nF capacitor should be placed between this pin and analog ground. ADC Filter Capacitor Connection (positive right-channel input to modulator). A 1 nF capacitor should be placed between this pin and analog ground. ADC Filter Capacitor Connection (negative right-channel input to modulator). A 1 nF capacitor should be placed between this pin and analog ground. PLL Power. 3.3 V nominal. Bypass capacitors should be placed close to this pin and connected directly to the PLL ground. PLL Loop Filter Connection. PLL Ground. Connect to DGND. Composite Video Input. Composite video signal input to the sync separator. The sync output is connected to a PLL that generates the clocks for the AD1970. This pin has an input impedance of 2 kΩ. No Connect. PLL Mode Select Pin 0. The setting of these pins indicates the source and frequency of the input clock to generate the internal MCLK for the AD1970. PLL Mode Select Pin 1. The setting of these pins indicates the source and frequency of the input clock to generate the internal MCLK for the AD1970. Master Clock Input. This input is used to generate the internal master clock if it is not derived from the composite video signal on VID_IN. The master clock frequency must be either fs or 256 × fs, where fs is the input sampling frequency. The PLL_CTRLx pins should be set to accept the appropriate MCLK input frequency. Video Present Flag. A high logic level on this pin indicates that a valid composite video signal is present on the VID_IN pin. Open-drain output. Crystal Oscillator Output. This pin is the output of the on-board oscillator and should be connected to one side of a crystal. Crystal Oscillator Input. This pin is the input to the on-board oscillator and should be connected to one side of a crystal. General Purpose I/O 0. This pin can be set to be either a static input or output, with levels and direction controlled through the I2C port. General Purpose I/O 1. This pin can be set to be either a static input or output, with levels and direction controlled through the I2C port. Digital Ground. Digital Power. General Purpose I/O 2. This pin can be set to be either a static input or output, with levels and direction controlled through the I2C port. General Purpose I/O 3. This pin can be set to be either a static input or output, with levels and direction controlled through the I2C port. Serial Data Input/Output (Before BTSC Encoding). Digital input to the BTSC encoder or output of the ADC. The serial format is selected by writing to Bits 3:2 of Control Register 1. Bit Clock Input/Output. Serial bit clock for clocking in the serial data. The interpretation of BCLK changes according to the serial mode, which is set by writing to the control registers. Left/Right Clock Input/Output. Left/right clock for framing the serial input data. The interpretation of the LRCLK changes according to the serial mode, set by writing to the control registers. Digital Input Enable (active high). I2C Serial Data Input/Output. I2C Serial Clock Input. I2C Address 1. The address of the I2C port is set by these pins according to Table 16. I2C Address 0. The address of the I2C port is set by these pins according to Table 16. Digital Ground. Rev. 0 | Page 8 of 20 AD1970 THEORY OF OPERATION The AD1970 is comprised of a BTSC encoder with stereo analog inputs and a sync separator to derive the pilot signal from the composite video stream. Figure 1 shows the block diagram of the device. Signal processing parameters are stored in a parameter RAM, which is initialized on power-up by an internal boot ROM. The values stored in the parameter RAM control all the filter coefficients, mixing, and dynamics-processing code used in the BTSC algorithm. The AD1970 has an I2C port that supports complete read/write capability of the parameter RAM, as well as a control port and several other registers that allow the various signal processing parameters to be controlled. The AD1970 can run as a standalone processor without external control. The AD1970 has a very flexible serial data input port that allows for glueless interconnection to a variety of digital signal sources. The AD1970 can be configured in left-justified, I2S, rightjustified, or DSP serial port-compatible modes. It can support 16, 20, and 24 bits in all modes. The AD1970 accepts serial audio data in MSB first, twos complement format. The AD1970 operates from a single 3.3 V power supply. It is fabricated on a single monolithic integrated circuit and is housed in a 48-pin LQFP package for operation over the temperature range of 0°C to 70°C. Rev. 0 | Page 9 of 20 AD1970 SIGNAL PROCESSING BACKGROUND OF BTSC For the receiver to recover this L − R signal, a pilot tone at the horizontal rate is added to the signal. The receiver has a PLL that locks to this pilot and generates a signal at the carrier frequency. This signal is then used to multiply the composite BTSC-encoded signal, which translates this component back down to baseband. Once the L + R and L − R signals are recovered, a simple addition/subtraction circuit (sometimes referred to as the matrix) can be used to recover the right signal. Since the pilot tone is added at 15.734 kHz, it is necessary to reduce the bandwidth of the signal so that audio signals cannot interfere with the pilot tone. In the AD1970, the bandwidth is limited to 14 kHz; above this frequency, the response decays very rapidly. BTSC is the name of the standard for adding stereo audio capability to the US television system. It is in many ways similar to the algorithm used for FM stereo broadcasts, with the addition of a sophisticated compressor circuit to improve the signal-tonoise ratio. To maintain compatibility with non-BTSC TV receivers, the processing of mono (L = R) signals is unchanged from the original pre-BTSC system. The L + R signal is applied to a 75 µs pre-emphasis filter, and is then applied to a 4.5 MHz FM modulator, which is later added to the video signal to create a composite video signal. PERFORMANCE FACTORS Stereo capability is added by taking the L − R signal, applying it to a 2-band dynamic compressor, and then multiplying this signal by a carrier signal at twice the horizontal scanning rate (Fh), or about 2 × 15.734 kHz. This multiplication is known as double sideband, suppressed-carrier modulation, and it effectively translates the compressed L − R spectrum up in frequency so that it sits above the audio band (see Figure 3). L–R To maintain good separation between the left and right channels, it is necessary to closely match the filtering and companding standards set forth in the standard (FCC OET60). Even small errors can result in poor performance. The AD1970 has been programmed to match these standards as accurately as possible. Typical separation numbers range from 30 dB at frequencies below 500 Hz to 15 dB at 13.5 kHz. Measuring these numbers can be difficult, since significant differences exist between many units sold as reference decoders, which are all implemented with analog components. COMPRESSOR 2× Fh CARRIER L OSCILLATOR MATRIX MAIN ALGORITHM FLOW 75µs PRE-EMPH FILTER 1/X RMS DETECT GAIN BANDPASS SECOND ORDER NONLINEAR FORMULA RMS DETECT GAIN BANDPASS FOURTH ORDER LPF EIGHT ORDER PRE-EMPH SECOND ORDER SPECTRAL TILT FILTER Figure 3. Signal Processing Flow Rev. 0 | Page 10 of 20 05500-003 L+R L-R IN TO DAC Fh PILOT R AD1970 SEPARATION ALIGNMENT The BTSC encoder outputs are all specified in terms of the deviation of the FM 4.5 MHz carrier. For the AD1970, a digital input level of 0 dB (mono signal) should cause a carrier deviation of ±25 kHz without the 75 µs pre-emphasis filter. In practice, the pre-emphasis filter can be left in for this adjustment, as long as the frequency is low enough to not be affected by the filter. It is critical to maintain the proper gain relationship between the BTSC encoder and the 4.5 MHz FM modulator. A common mistake is to assume that changing the gain between the BTSC encoder output and the FM modulator input has the same effect as changing the audio input level going in to the BTSC encoder. The presence of a complicated 2-band nonlinear dynamics processor means that the encoder output must be connected to the decoder input (through the FM modulation/ demodulation process) with a known gain. If this gain is changed, then the separation significantly suffers. When measuring the AD1970 on the bench, it is possible to use a BTSC reference decoder box, so that the FM modulation/ demodulation process can be skipped. These units have a method of adjusting the input voltage sensitivity to achieve best separation. The output level of the AD1970 can also be adjusted over a wide range using either the I2C control port or by adjusting the values of the components used in the external analog low-pass filter that is between the BTSC encoder output and the input to the FM modulator. PHASE LINEARITY OF THE EXTERNAL ANALOG FILTER If the time-alignment of the pilot to the carrier signal is not close to 0°, a loss of separation can occur. This means that the external analog low-pass filter should be a linear-phase design to provide constant group delay over the range from dc to 50 kHz. A Bessel filter is recommended for this application. The typical applications circuit (see Figure 8) shows a recommended design for this filter. INPUT LEVELS The maximum input level to the AD1970 changes across frequency. Table 14 shows the maximum allowable input level for different frequencies. These values are part of the BTSC specification, not a function of this chip. Table 14. Maximum Input Levels to the BTSC Encoder across Frequency Frequency (Hz) 20 to 1000 1600 2500 3150 5000 8000 12500 Maximum Input Level (dBFS) 0 −1 −3 −5 −8 −11 −15 CLOCKING AND PLL The AD1970’s master clock either can be directly fed to the MCLK pin or generated by a PLL from a composite video signal input on the VID_IN pin. If the clock input is on the MCLK pin, the PLL can synthesize the internal clocks from either a clock at the digital audio frame sync frequency (fS = 48 kHz) or 256 × fS. The PLL mode is controlled by Pins PLL_MODE0 and PLL_MODE1. The settings are shown in Table 15. Table 15. PLL Modes PLL_MODE1 0 PLL_MODE0 0 0 1 1 1 0 1 Setting Composite video input (on VID_IN) 256 × fs (on MCLK) fs (on MCLK) PLL bypass CRYSTAL OSCILLATOR The AD1970 has an on-board crystal oscillator to generate a clock that can be used by an RF modulator or other application. For example, a 4 MHz crystal can be connected as shown in the application circuit (see Figure 8). The AD1970 does not use this clock itself, so if it is not needed in an application the XIN pin should be grounded and the XOUT pin left unconnected. GENERAL PURPOSE INPUT/OUTPUT (GPIO) PINS Pins GPIO0, GPIO1, GPIO2, and GPIO3 are set to be inputs or outputs by Bits 19:16 of Control Register 2. All four default to input state. These pins do not take an input to or send an output from the main signal flow. When set as an output, the binary value on the pins is set according to Bits 15:12 of Control Register 2. These pins can be used to interface with I/O pins on a microcontroller and allow hardware control via the I2C bus. POWER-UP SEQUENCE The AD1970 has a built-in power-up sequence that initializes the contents of all internal RAMs. During this time, the parameter RAM is filled with values from its associated boot ROM. The data memories are also cleared during this time. The boot sequence lasts for 1024 MCLK cycles and starts on the rising edge of the RESETB pin. The user should avoid writing to or reading from the I2C registers during this period of time. Rev. 0 | Page 11 of 20 AD1970 CONTROL PORT I2C PORT OVERVIEW The AD1970 can be controlled using the I2C port. In general, there are three parameters that can be controlled: the encoder output level, the Phat Stereo image enhancement algorithm, and the dialog enhancement algorithm. It is also possible to write new data into the parameter RAM to alter the filter coefficients used in the BTSC encoding process. Since this is a fairly complex topic and is unnecessary for normal operation of the chip, the details are not included in this data sheet; please contact ADI sales if modifications to the BTSC filters are required. 2 The I C port uses a 2-wire interface consisting of SDA, the bidirectional data line, and SCL, the clock. The R/W bit is low for a write operation and high for a read operation. The 10-bit address word is decoded into either a location in the parameter RAM or one of the registers. The number of data bytes varies according to the register or memory being accessed. The detailed data format diagram for continuous-mode operation is given in the section. I2C ADDRESS DECODING Table 16 shows the address decoding used in the I2C port. Four different addresses are available to avoid conflicting addresses on an I2C bus. The I2C address space encompasses a set a registers and the parameter RAM. The parameter RAM is loaded on power-up from an on-board boot ROM. Table 16. I2C Address Settings ADR1 0 0 1 1 ADR0 0 1 0 1 I2C Address 0x20 0x21 0x22 0x23 Table 17. I2C Port Address Decoding Register Address 0 Register Name Input Level Control Read/Write Word Length Write: 22 bits Read: 22 bits 1 to 254 255 256 Parameter RAM Output Level Control Control Register 1 257 258 259 260 Control Register 2 ADC Volume Control Stereo Spreading Control Dialog Enhancement Control Rev. 0 | Page 12 of 20 Write: 11 bits Read: 6 bits Write: 22 bits AD1970 Table 18. Control Register 1 Write INPUT LEVEL CONTROL This register location controls the input level of both the left and right channels to the AD1970 BTSC encoding algorithm. The register defaults to a value of 1.0 (0100000000000000000000 in binary 2.20 format) and allows a maximum of 12 dB of gain at a full-scale value. This feature allows compatibility with the Dolby digital specification for proper operation in both RF mode and line mode. In RF mode, the dialog level is specified at 11 dB higher than the dialog level in line mode. A gain of 11 dB can be achieved by writing 1.8836 to Address 0. Register Bits 10:8 7 6 5:4 3:2 1:0 OUTPUT LEVEL CONTROL The level control of the BTSC-encoded output is controlled in this register location. The default value is 0.5 (–6 dB, 0010000000000000000000 in binary 2.20 format), or 250 mV on the DAC output. The output level should not be used as a volume control. Its intended use, in conjunction with the output filter, is to match the level with the expected input of the BTSC decoder. Matching these allows maximum separation between the left and right encoded channels. Control Register 1 Control Register 1 is an 11-bit register that controls serial modes, de-emphasis, mute, power-down, and I2C-to-memory transfers. Table 18 documents the contents of this register. Function Reserved, set to 000 Soft mute (1 = start mute sequence) Soft power-down (1 = power-down) Reserved, set to 00 Serial-In mode 00 = I2S 01 = Right-justified 10 = DSP 11 = Left-justified Word length 00 = 24 bits 01 = 20 bits 10 = 16 bits 11 = 16 bits Table 19. Control Register 1 Read Register Bits 5:2 1:0 Function GPIO 3:0 read back Reserved Control Register 2 Control Register 2 is a 22-bit write-only register that controls power down modes, PLL and sync separator controls, and digital I/O pin functions. Bits 5:4 and 10:8 are reserved and should be set to 0 at all times. Table 20. Control Register 2 The audio signal is muted with Bit 7 of the control register. Register Bits 21 20 19:16 15:12 11:9 8:4 3 2 1 0 The soft power-down bit (Bit 6) stops the internal clocks to the DSP core, but does not reset the part. The digital power consumption is reduced to a low level when this bit is asserted. Reset can only be asserted using the external reset pin. Bits 3:2 select the serial format from one of four modes. These different formats are discussed in the section of this data sheet. The word length bits (1:0) are used in right-justified serial modes to determine where the MSB is located relative to the start of the audio frame. Function Enable ADC output on serial audio interface Reserved GPIO output enable 3:0 GPIO data PLL shift, default 100 Sync separator slicer voltage; default 10111 ADC power-down Reference power-down DAC power-down PLL power-down ADC Volume Control Register This controls the input level of both ADC channels. The default value is 1.0 (0100000000000000000000 in binary 2.20 format). Stereo Spreading Register This register controls ADI’s patented Phat Stereo spatial enhancement algorithm. The default is all 0s, which corresponds to no effect. The maximum setting is 0100000000000000000000 or a twos complement fractional value of 1.0. Note that the bass energy in each channel is increased using this algorithm, which may cause some digital clipping on full-scale signal peaks, especially at low frequencies. Rev. 0 | Page 13 of 20 AD1970 Dialog Enhancement Register I2C READ/WRITE DATA FORMATS This controls the built-in dialog enhancement algorithm, and defaults to 0. The maximum setting is 0100000000000000000000 or a twos complement fractional value of 1.0. This algorithm is intended to solve the problem of playing back high dynamic range digital audio signals over a television’s built-in speakers. It provides an amplitude boost to signals that are in the range where dialog signals are usually found, while at the same time preventing loud special effects passages from overloading the speakers or amplifiers. The read/write formats of the I2C port are designed to be byte oriented. This allows for easy programming of common microcontroller chips. In order to fit into a byte oriented format, 0s are appended to the data fields in order to extend the data word to the next multiple of 8 bits. For example, 22-bit words written to the parameter RAM are appended with two leading zeroes in order to reach 24 bits (3 bytes). These zero-extended data fields are appended to a 2-byte field consisting of a read/write bit and a 10-bit address. The I2C port knows how many data bytes to expect based on the address received in the first two bytes. SCL 0 SDA 0 1 0 0 AD1 0 AD0 R/W 0 ACK. BY I2C WRITE AD1970 START BY MASTER 0 0 R/W 0 FRAME 1 CHIP ADDRESS BYTE 0 1 0 0 0 0 0 0 0 1 ACK. BY AD1970 ACK. BY AD1970 REGISTER WRITE FRAME 2 REGISTER ADDRESS UPPER BYTE FRAME 3 REGISTER ADDRESS LOWER BYTE SCL (CONTINUED) D15 D14 D11 D12 D13 D10 D9 D8 D7 D5 D6 D4 D3 D2 D1 D0 ACK. BY AD1970 ACK. BY STOP BY AD1970 MASTER FRAME 4 REGISTER DATA UPPER BYTE 05500-009 SDA (CONTINUED) FRAME 5 REGISTER DATA LOWER BYTE Figure 4. Sample of I2C Write Format (Control Register 1 Write) SCL SDA 0 1 0 0 0 AD1 AD0 R/W 0 ACK. BY I2C WRITE AD1970 START BY MASTER FRAME 1 CHIP ADDRESS BYTE 0 0 0 0 R/W 0 0 1 REGISTER READ FRAME 2 REGISTER ADDRESS UPPER BYTE 0 0 0 0 0 0 ACK. BY AD1970 1 ACK. BY AD1970 FRAME 3 REGISTER ADDRESS LOWER BYTE SCL (CONTINUED) 0 REPEATED START BY MASTER 1 0 0 0 AD1 AD0 R/W FRAME 4 CHIP ADDRESS BYTE D7 I2C ACK. BY READ AD1970 D6 D5 D4 D3 D2 FRAME 5 REGISTER DATA BYTE D1 D0 ACK. BY STOP BY MASTER MASTER Figure 5. Sample of I2C Read Format (Control Register 1 Read) Rev. 0 | Page 14 of 20 05500-008 SDA (CONTINUED) AD1970 Table 21. Control Register 1 Write Format Byte 0 00000, R/W = 0, Adr [9:8] Byte1 Adr [7:0] Byte 2 00000, Bit [10:8] Byte 3 Bit [7:0] Table 22. Control Register 1 Read Format Byte 0 00000, R/W = 1, Adr [9:8] Byte 1 Adr [7:0] Byte 2 00, Bit [5:0] Table 23. Control Register 2 Write Format Byte 0 00000, R/W = 0, Adr [9:8] Byte 1 Adr [7:0] Byte 2 00, Bit [21:16] Byte 3 Bit [15:8] Byte 4 Bit [7:0] Table 24. Input/Output Level Control, ADC Volume Control, Stereo Spreading, and Dialog Enhancement Registers Write Format Byte 0 00000, R/W = 0, Adr [9:8] Byte 1 Adr [7:0] Byte 2 00, Level [21:16] Rev. 0 | Page 15 of 20 Byte 3 Level [15:8] Byte 4 Level [7:0] AD1970 ANALOG INPUT/OUTPUT ADC INPUT SERIAL DATA PORT The AD1970 accepts an analog left-right signal on its input. The AD1970’s flexible serial audio interface accepts and sends data in twos complement, MSB first format. The left channel data field always precedes the right channel data field. The serial mode is set by using mode select bits in the control register. In all modes except for the right justified mode, the serial port accepts an arbitrary number of bits up to a limit of 24 (extra bits do not cause an error, but they are truncated internally). In the right-justified mode, control register bits are used to set the word length to 16, 20, or 24 bits. The default on power-up is 24bit mode. Proper operation of the right justified mode requires that there be exactly 64 BCLKs per audio frame. DAC OUTPUT Figure 6 shows the block diagram of the analog output. A series of current sources are controlled by a digital Σ-Δ modulator. Depending on the digital code from the modulator, each current source is connected to the summing junction of either a positive I-to-V converter or a negative I-to-V converter. Two extra current sources that push instead of pull are added to set the midscale common-mode voltage. All current sources are derived from the VREF input pin. The gain of the AD1970 is directly proportional to the magnitude of the current sources, and therefore the gain of the AD1970 is proportional to the voltage generated on the VREF pin. The nominal VREF voltage is 1.5 V. IREF Figure 7 shows the left-justified mode. LRCLK is high for the left channel, and low for the right channel. Data is sampled on the rising edge of BCLK. The MSB is left-justified to a LRCLK transition, with no MSB delay. The left-justified mode can accept any word length up to 24 bits. IREF OUT+ Figure 7 shows the I2S mode, which is the default setting. LRCLK is low for the left channel and the MSB is delayed from the edge of the LRCLK by a single BCLK period. The I2S mode can be used to accept any number of bits up to 24. OUT– VREF IN IREF + DIG_IN IREF – DIG_IN Figure 7 shows the right-justified mode of the AD1970. LRCLK is high for the left channel, low for the right channel. Data is sampled on the rising edge of BCLK. The start of data is delayed from the LRCLK edge by 16, 12, or 8 BCLK intervals, depending on the selected word length. The default word length is 24 bits; other word lengths are set by writing to Bits 1:0 of the control register. In right-justified mode, it is assumed that there are 64 BCLKs per frame. SWITCHED CURRENT SOURCES 05500-005 BIAS FROM DIGITAL Σ–∆ MODULATOR (DIG_IN) SERIAL DATA MODES Figure 6. Internal DAC Analog Architecture Since the VREF input effectively multiplies the signal, care must be taken to insure that no ac signals appear on this pin. This can be accomplished by using a large decoupling capacitor connected to VREF. The AD1970 should be used with an external third order filter on each output channel, as shown in Figure 8. The values shown are for a 100 kHz Bessel filter. The use of a Bessel filter is important to maintain the time-alignment of the pilot to the carrier. If these signals are not in phase, a loss of separation occurs. Figure 7 shows the DSP serial port mode. LRCLK must pulse high for at least one bit clock period before the MSB of the left channel is valid and LRCLK must pulse high again for at least one bit clock period before the MSB of the right channel is valid. Data is sampled on the falling edge of BCLK. The DSP serial port mode can be used with any word length up to 24 bits. In this mode, it is the responsibility of the DSP to ensure that the left data is transmitted with the first LRCLK pulse and that synchronism is maintained from that point forward. For best performance, a large (>10 µF) capacitor should be connected between the FILTCAP pin and analog ground. Rev. 0 | Page 16 of 20 AD1970 RIGHT CHANNEL LRCLK LEFT CHANNEL BCLK SDATA MSB MSB LSB LSB LEFT JUSTIFIED MODE: 16 TO 24 BITS PER CHANNEL LEFT CHANNEL LRCLK RIGHT CHANNEL BCLK MSB SDATA I2S LSB LSB MSB MODE: 16 TO 24 BITS PER CHANNEL LEFT CHANNEL RIGHT CHANNEL LRCLK BCLK SDATA LSB MSB MSB LSB RIGHT JUSTIFIED MODE: SELECT NUMBER OF BITS PER CHANNEL LRCLK BCLK MSB LSB MSB LSB DSP MODE: 16 TO 24 BITS PER CHANNEL 1/FS NOTES: 1. DSP MODE DOESN'T IDENTIFY CHANNEL. 2. LRCLK NORMALLY OPERATES AT Fs EXCEPT FOR DSP MODE WHICH IS 2xFs. 3. BCLK FREQUENCY IS NORMALLY 64xLRCLK BUT MAY BE OPERATED IN BURST MODE. Figure 7. Serial Data Formats Rev. 0 | Page 17 of 20 05500-006 SDATA AD1970 TYPICAL APPLICATIONS CIRCUIT 3.3V C21 0.1µF C20 0.1µF L1 600Z L2 600Z C22 0.1µF C19 0.1µF C23 0.1µF C18 4.7µF + R2 10kΩ C3 1nF C4 1nF C5 1nF PLL_LF ADR0 ADR1 SCL SDA 43 DIG_IN_EN 42 LRCLK 41 BCLK 40 SDATA GPIO3 39 38 GPIO2 35 GPIO1 34 GPIO0 C6 1nF AD1970 R11 10kΩ 28 PLL_MODE0 29 PLL_MODE1 31 VID_PRES 26 VIDEO_IN C27 470pF C7 1nF 30 PLL_MODE0 PLL_MODE1 VID_PRES VID_IN RESET MCLK 3 AGND 2 11 VREF 12 FILTCAP 27 NC 5 RSVD AGND DGND DGND C15 270pF ADR0 ADR1 R6 11kΩ DIG_IN_EN LRCLK_INTF BCLK_INTF SDATA_INTF GPIO3 GPIO2 GPIO1 GPIO0 R9 604Ω R7 11kΩ C14 68pF R8 3.01kΩ C13 10µF BTSC + R10 49.9kΩ C12 2.2nF RESET C10 10µF + + C11 10µF OPTIONAL AUXILIARY OSCILLATOR C9 22pF 05500-007 C8 22pF 48 Y1 4MHz 4MHz 36 R13 1kΩ DGND 33 XIN 32 XOUT 24 47 46 45 44 SDA C16 2.2µF BTSC_OUT 9 7 VIN_OAMP VOUT_OAMP 6 3.3V R12 1kΩ SCL C17 + 0.1µF 14 + C25 4.7µF R15 2kΩ 23 15 VOUT_IAMPL 16 VIN_IAMPL 17 VOUT_IAMPR 18 VIN_IAMPR 19 CAPLP 20 CAPLN 21 CAPRP 22 CAPRN + R14 2kΩ R5 1.6kΩ PVDD R1 10kΩ 10 AUDIO_IN_RIGHT C2 82pF PGND AUDIO_IN_LEFT R4 10kΩ 25 C26 4.7µF C1 82pF 8 AVDD 13 AVDD R3 10kΩ 1 DVDD 4 DVDD 37 DVDD C24 0.1µF 3.3V Figure 8. Typical Applications Circuit Rev. 0 | Page 18 of 20 AD1970 OUTLINE DIMENSIONS 0.75 0.60 0.45 9.00 BSC SQ 1.60 MAX 37 48 36 1 PIN 1 0.15 0.05 7.00 BSC SQ TOP VIEW 1.45 1.40 1.35 SEATING PLANE 0.20 0.09 7° 3.5° 0° 0.08 MAX COPLANARITY (PINS DOWN) 25 12 13 VIEW A 0.50 BSC LEAD PITCH VIEW A 24 0.27 0.22 0.17 ROTATED 90° CCW COMPLIANT TO JEDEC STANDARDS MS-026-BBC Figure 9. 48-Lead Low-Profile Quad Flat Package [LQFP] (ST-48) Dimensions are shown in millimeters ORDERING GUIDE Model AD1970JSTZ1 AD1970JSTZRL1 1 Temperature Range 0°C to 70°C 0°C to 70°C Package Description 48-Lead LQFP 48-Lead LQFP on 13-inch Reel Z = Pb-free part. Rev. 0 | Page 19 of 20 Package Option ST-48 ST-48 AD1970 NOTES Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. © 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05500–0–4/05(0) Rev. 0 | Page 20 of 20