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4 ADC/8 DAC with PLL, 192 kHz, 24-Bit CODEC AD1938
FEATURES
PLL generated or direct master clock Low EMI design 108 dB DAC/107 dB ADC dynamic range and SNR -94 dB THD + N Single 3.3 V supply Tolerance for 5 V logic inputs Supports 24 bits and 8 kHz to 192 kHz sample rates Differential ADC input Single-ended DAC output Log volume control with autoramp function SPI(R) controllable for flexibility Software controllable clickless mute Software power-down Right justified, left justified, I2S and TDM modes Master and slave modes up to 16-channel in/out 48-lead LQFP package
GENERAL DESCRIPTION
The AD1938 is a high performance, single-chip codec that provides four analog-to-digital converters (ADCs) with differential input and eight digital-to-analog converters (DACs) with single-ended output using the Analog Devices, Inc. patented multibit sigma-delta (-) architecture. An SPI port is included, allowing a microcontroller to adjust volume and many other parameters. The AD1938 operates from 3.3 V digital and analog supplies. The AD1938 is available in a 48-lead (single-ended output) LQFP package. Other members of this family include a differential DAC output and I2C(R) control port version. The AD1938 is designed for low EMI. This consideration is apparent in both the system and circuit design architectures. By using the on-board PLL to derive the master clock from the LR clock or from an external crystal, the AD1938 eliminates the need for a separate high frequency master clock and can also be used with a suppressed bit clock. The digital-to-analog and analog-to-digital converters are designed using the latest ADI continuous time architectures to further minimize EMI. By using 3.3 V supplies, power consumption is minimized, further reducing emissions.
APPLICATIONS
Automotive audio systems Home Theater Systems Set-top boxes Digital audio effects processors
FUNCTIONAL BLOCK DIAGRAM
DIGITAL AUDIO INPUT/OUTPUT
AD1938
SERIAL DATA PORT DAC DAC ADC ANALOG AUDIO INPUTS ADC ADC ADC DIGITAL FILTER SDATA OUT SDATA IN CLOCKS TIMING MANAGEMENT AND CONTROL (CLOCK AND PLL) DAC DIGITAL FILTER AND VOLUME CONTROL DAC DAC DAC DAC DAC PRECISION VOLTAGE REFERENCE CONTROL PORT SPI/I2C ANALOG AUDIO OUTPUTS
CONTROL DATA INPUT/OUTPUT
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.
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05582-001
AD1938 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Test Conditions............................................................................. 3 Analog Performance Specifications ........................................... 3 Crystal Oscillator Specifications................................................. 4 Digital Input/Output Specifications........................................... 5 Power Supply Specifications........................................................ 5 Digital Filters................................................................................. 6 Timing Specifications .................................................................. 6 Absolute Maximum Ratings............................................................ 8 Thermal Resistance ...................................................................... 8 ESD Caution.................................................................................. 8 Pin Configuration and Function Descriptions............................. 9 Typical Performance Characteristics ........................................... 11 Theory of Operation ...................................................................... 13 Analog-to-Digital Converters (ADCs).................................... 13 Digital-to-Analog Converters (DACs) .................................... 13 Clock Signals............................................................................... 13 Reset and Power-Down ............................................................. 14 Serial Control Port ..................................................................... 14 Power Supply and Voltage Reference....................................... 15 Serial Data Ports--Data Format............................................... 15 Time-Division Multiplexed (TDM) Modes............................ 15 Daisy-Chain Mode ..................................................................... 19 Control Registers ............................................................................ 24 Definitions................................................................................... 24 PLL and Clock Control Registers............................................. 24 DAC Control Registers .............................................................. 25 ADC Control Registers.............................................................. 27 Additional Modes....................................................................... 29 Application Circuits ....................................................................... 30 Outline Dimensions ....................................................................... 31 Ordering Guide .......................................................................... 31
REVISION HISTORY
5/06--Revision 0: Initial Version
Rev. 0 | Page 2 of 32
AD1938 SPECIFICATIONS
TEST CONDITIONS
Performance of all channels is identical, exclusive of the interchannel gain mismatch and interchannel phase deviation specifications.
Supply voltages (AVDD, DVDD) Temperature range 1 Master clock Input sample rate Measurement bandwidth Word width Load capacitance (digital output) Load current (digital output) Input voltage HI Input voltage LO
1
3.3 V As specified in Table 1 and Table 2 12.288 MHz (48 kHz fS, 256 x fS mode) 48 kHz 20 Hz to 20 kHz 24 bits 20 pF 1 mA or 1.5 k to 1/2 DVDD supply 2.0 V 0.8 V
Functionally guaranteed at -40C to +125C case temperature.
ANALOG PERFORMANCE SPECIFICATIONS
Specifications guaranteed at 25C (ambient). Table 1.
Parameter ANALOG-TO-DIGITAL CONVERTERS ADC Resolution Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) Total Harmonic Distortion + Noise Gain Error Interchannel Gain Mismatch Offset Error Gain Drift Interchannel Isolation CMRR Input Resistance Input Capacitance Input Common-Mode Bias Voltage DIGITAL-TO-ANALOG CONVERTERS Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) With A-Weighted Filter (Avg) Total Harmonic Distortion + Noise Single-Ended Version Single-Ended Version Full-Scale Output Voltage Gain Error Interchannel Gain Mismatch Offset Error Gain Drift Interchannel Isolation Conditions All ADCs 20 Hz to 20 kHz, -60 dB input 98 100 -1 dBFS -10 -0.25 -10 Min Typ 24 102 105 -96 Max Unit Bits dB dB dB % dB mV ppm/C dB dB dB k pF V
100 mV rms, 1 kHz 100 mV rms, 20 kHz
0 100 -110 55 55 14 10 1.5
-87 +10 +0.25 +10
20 Hz to 20 kHz, -60 dB input 98 100 0 dBFS Two channels running Eight channels running -10 -0.2 -16 -30 104 106 108 -92 -86 0.88 (2.48) dB dB dB dB dB V rms (V p-p) % dB mV ppm/C dB
-75 +10 +0.2 +16 +30
-4 100
Rev. 0 | Page 3 of 32
AD1938
Parameter Interchannel Phase Deviation Volume Control Step Volume Control Range De-emphasis Gain Error Output Resistance at Each Pin REFERENCE Internal Reference Voltage External Reference Voltage Common-Mode Reference Output Conditions Min Typ 0 0.375 95 100 FILTR pin FILTR pin CM pin 1.50 1.50 1.50 Max Unit Degrees dB dB dB V V V
0.6
1.32
1.68
Specifications measured at 130C (case). Table 2.
Parameter ANALOG-TO-DIGITAL CONVERTERS ADC Resolution Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) Total Harmonic Distortion + Noise Gain Error Interchannel Gain Mismatch Offset Error DIGITAL-TO-ANALOG CONVERTERS Dynamic Range No Filter (RMS) With A-Weighted Filter (RMS) With A-Weighted Filter (Average) Total Harmonic Distortion + Noise Single-Ended Version Single-Ended Version Full-Scale Output Voltage Gain Error Interchannel Gain Mismatch Offset Error Gain Drift REFERENCE Internal Reference Voltage External Reference Voltage Common-Mode Reference Output Conditions All ADCs 20 Hz to 20 kHz, -60 dB input 95 97 -1 dBFS -10 -0.25 -10 20 Hz to 20 kHz, -60 dB input 98 100 0 dBFS Two channels running Eight channels running -10 -0.2 -16 -30 FILTR pin FILTR pin CM pin 104 106 108 -92 -86 0.8775 (2.482) dB dB dB dB dB V rms (V p-p) % dB mV ppm/C V V V Min Typ 24 102 105 -96 Max Unit Bits dB dB dB % dB mV
0
-87 +10 +0.25 +10
-70 +10 +0.2 16 30
-4
1.32
1.50 1.50 1.50
1.68
CRYSTAL OSCILLATOR SPECIFICATIONS
Table 3.
Parameter TRANSCONDUCTANCE Min Typ 3.5 Max Unit mmhos
Rev. 0 | Page 4 of 32
AD1938
DIGITAL INPUT/OUTPUT SPECIFICATIONS
-40C < TA < +130C, DVDD = 3.3 V 10%. Table 4.
Parameter Input Voltage HI (VIH) Input Voltage HI (VIH) Input Voltage LO (VIL) Input Leakage High Level Output Voltage (VOH) Low Level Output Voltage (VOL) Input Capacitance Conditions/Comments MCLK_I pin IIH @ VIH = 2.4 V IIL @ VIL = 0.8 V IOH = 1 mA IOL = 1 mA Min 2.0 2.2 Typ Max Unit V V V A A V V pF
0.8 10 10 DVDD - 0.60 0.4 5
POWER SUPPLY SPECIFICATIONS
Table 5.
Parameter SUPPLIES Voltage Conditions/Comments Min Typ Max Unit
Digital Current Normal Operation
Power-Down Analog Current Normal Operation Power-Down DISSIPATION Operation All Supplies Digital Supply Analog Supply Power-Down, All Supplies POWER SUPPLY REJECTION RATIO Signal at Analog Supply Pins
DVDD AVDD MCLK = 256 fS fS = 48 kHz fS = 96 kHz fS = 192 kHz fS = 48 kHz to 192 kHz
3.0 3.0
3.3 3.3 56 65 95 2.0 74 23
3.6 3.6
V V mA mA mA mA mA mA
MCLK = 256 fS, 48 kHz 429 185 244 83 1 kHz, 200 mV p-p 20 kHz, 200 mV p-p 50 50 mW mW mW mW dB dB
Rev. 0 | Page 5 of 32
AD1938
DIGITAL FILTERS
Table 6.
Parameter ADC DECIMATION FILTER Pass Band Pass-Band Ripple Transition Band Stop Band Stop-Band Attenuation Group Delay DAC INTERPOLATION FILTER Pass Band Mode All modes, typ @ 48 kHz Factor 0.4375 fS 0.5 fS 0.5625 fS 79 22.9844/fS 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 48 kHz mode, typ @ 48 kHz 96 kHz mode, typ @ 96 kHz 192 kHz mode, typ @ 192 kHz 0.4535 fS 0.3646 fS 0.3646 fS 479 22 35 70 0.01 0.05 0.1 0.5 fS 0.5 fS 0.5 fS 0.5465 fS 0.6354 fS 0.6354 fS 70 70 70 25/fS 11/fS 8/fS 521 115 42 24 48 96 26 61 122 Min Typ 21 0.015 24 27 Max Unit kHz dB kHz kHz dB s kHz kHz kHz dB dB dB kHz kHz kHz kHz kHz kHz dB dB dB s s s
Pass-Band Ripple
Transition Band
Stop Band
Stop-Band Attenuation
Group Delay
TIMING SPECIFICATIONS
-40C < TA < +130C, DVDD = 3.3 V 10%. Table 7.
Parameter INPUT MASTER CLOCK (MCLK) AND RESET tMH tMH fMCLK fMCLK tPDR tPDRR PLL Lock time 256 fS VCO Clock Output Duty Cycle MCLK_O pin MCLK frequency RST low RST recovery MCLK and LRCLK input 40 Condition Comments Min Max Unit
MCLK duty cycle
DAC/ADC clock source = PLL clock @ 256 fS, 384 fS, 512 fS, 768 fS DAC/ADC clock source = direct MCLK @ 512 fS (bypass on-chip PLL) PLL mode, 256 fS reference Direct 512 fS mode Reset to active output
40 40 6.9 15 4096
60 60 13.8 27.6
% % MHz MHz ns tMCLK ms %
10 60
Rev. 0 | Page 6 of 32
AD1938
Parameter SPI PORT tCCH tCCL fCCLK tCDS tCDH tCLS tCLH tCLH tCOE tCOD tCOH tCOTS DAC SERIAL PORT tDBH tDBL tDLS tDLH tDLS tDDS tDDH ADC SERIAL PORT tABH tABL tALS tALH tALS tABDD AUXILIARY INTERFACE tAXDS tAXDH tDXDD tXBH tXBL tDLS tDLH Condition CCLK high CCLK low CCLK frequency CDATA setup CDATA hold CLATCH setup CLATCH hold CLATCH high COUT enable COUT delay COUT hold COUT tri-state DBCLK high DBCLK low DLRCLK setup DLRCLK hold DLRCLK skew DSDATA setup DSDATA hold ABCLK high ABCLK low ALRCLK setup ALRCLK hold ALRCLK skew ASDATA delay AAUXDATA setup AAUXDATA hold DAUXDATA delay AUXBCLK high AUXBCLK low AUXLRCLK setup AUXLRCLK hold Comments See Figure 11 Min 35 35 10 To CCLK rising From CCLK rising To CCLK rising From CCLK falling From CCLK falling From CCLK falling From CCLK falling From CCLK falling See Figure 24 Slave mode Slave mode To DBCLK rising, slave mode From DBCLK rising, slave mode From DBCLK falling, master mode To DBCLK rising From DBCLK rising See Figure 25 Slave mode Slave mode To ABCLK rising, slave mode From ABCLK rising, slave mode From ABCLK falling, master mode From ABCLK falling To AUXBCLK rising From AUXBCLK rising From AUXBCLK falling 10 10 10 10 10 30 30 30 30 10 10 10 5 -8 10 5 10 10 10 5 -8 Max Unit ns ns MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
+8
+8 18
10 5 18 10 10 10 5
To AUXBCLK rising From AUXBCLK rising
Rev. 0 | Page 7 of 32
AD1938 ABSOLUTE MAXIMUM RATINGS
Table 8.
Parameter Analog (AVDD) Digital (DVDD) Input Current (Except Supply Pins) Analog Input Voltage (Signal Pins) Digital Input Voltage (Signal Pins) Operating Temperature Range (Case) Storage Temperature Range Rating -0.3 V to +3.6 V -0.3 to +3.6 V 20 mA -0.3 V to AVDD + 0.3 V -0.3 to DVDD + 0.3 V -40C to +125C -65C to +150C
THERMAL RESISTANCE
JA represents thermal resistance, junction-to-ambient; JC represents the thermal resistance, junction-to-case. All characteristics are for a 4-layer board. Table 9. Thermal Resistance
Package Type 48-Lead LQFP JA 50.1 JC 17 Unit C/W
Stresses above those listed under the Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; 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.
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 8 of 32
AD1938 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
ADC2RN ADC1RN ADC2RP ADC1RP ADC2LN ADC1LN ADC2LP ADC1LP AVDD
48 47 46 45 44 43 42 41 40 39 38
AGND MCLKI/XI MCLKO/XO AGND AVDD OL3 OR3 OL4 OR4
AVDD
37
CM
LF
1 2 3 4 5 6 7 8 9
36 35 34 33
AGND FILTR AGND AVDD AGND OR2 OL2 OR1 OL1 CLATCH/ADR1 CCLK/SCL DGND
AD1938
TOP VIEW (Not to Scale) SINGLE-ENDED OUTPUT
32 31 30 29 28 27 26 25
PD/RST 10 DSDATA4 11 DGND 12
13 14 15 16 17 18 19 20 21 22 23 24
COUT/SDA
DLRCLK
DSDATA3
DSDATA2
DSDATA1
ASDATA2
ASDATA1
ALRCLK
DBCLK
ABCLK
DVDD
CIN/ADR0
Figure 2. Pin Configuration, 48-Lead LQFP
Table 10. 48-Lead LQFP Package for AD1938
Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 In/Out I I O I I O O O O I I/O I I I/O I/O I I/O I/O I/O O I/O I/O I O I I I O Mnemonic AGND MCLKI/XI MCLKO/XO AGND AVDD OL3 OR3 OL4 OR4 PD/RST DSDATA4 DGND DVDD DSDATA3 DSDATA2 DSDATA1 DBCLK DLRCLK ASDATA2 ASDATA1 ABCLK ALRCLK CIN/ADR0 COUT/SDA DGND CCLK/SCL CLATCH/ADR1 OL1 Description Analog Ground. Master Clock Input/Crystal Oscillator Input. Master Clock Output/Crystal Oscillator Output. Analog Ground. Analog Power Supply. Connect to analog 3.3 V supply. DAC 3 Left Output. DAC 3 Right Output. DAC 4 Left Output. DAC 4 Right Output. Power-Down Reset (Active Low). DAC Input 4 (Input to DAC 4 L and R)/DAC TDM Data Out 2/AUX ADC 1 Data In. Digital Ground. Digital Power Supply. Connect to digital 3.3 V supply. DAC Input 3 (Input to DAC 3 L and R)/DAC TDM Data In 2/Aux DAC 2 Data Output. DAC Input 2 (Input to DAC 2 L and R)/DAC TDM Data Out/AUX ADC 1 Data In. DAC Input 1 (Input to DAC 1 L and R)/DAC TDM Data In/AUX ADC 2 Data In. Bit Clock for DACs. LR Clock for DACs. ADC Serial Data Output 2 (ADC 2 L and R)/ADC TDM Data Input/Aux DAC 1 Data Output. ADC Serial Data Output 1 (ADC 1 L and R)/ADC TDM Data Output. Bit Clock for ADCs. LR Clock for ADCs. Control Data Input (SPI). Control Data Output (SPI). Digital Ground. Control Clock Input (SPI). Latch Input for Control Data (SPI). DAC 1 Left Output.
Rev. 0 | Page 9 of 32
05582-020
AD1938
Pin No. 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 In/Out O O O I I I O I I O I I I I I I I I O I Mnemonic OR1 OL2 OR2 AGND AVDD AGND FILTR AGND AVDD CM ADC1LP ADC1LN ADC1RP ADC1RN ADC2LP ADC2LN ADC2RP ADC2RN LF AVDD Description DAC 1 Right Output. DAC 2 Left Output. DAC 2 Right Output. Analog Ground. Analog Power Supply. Connect to analog 3.3 V supply. Analog Ground. Voltage Reference Filter Capacitor Connection. Bypass with 10 F||100 nF to AGND. Analog Ground. Analog Power Supply. Connect to analog 3.3 V supply. Common-Mode Reference Filter Capacitor Connection. Bypass with 47 F||100 nF to AGND. ADC1 Left Positive Input. ADC1 Left Negative Input. ADC1 Right Positive Input. ADC1 Right Negative Input. ADC2 Left Positive Input. ADC2 Left Negative Input. ADC2 Right Positive Input. ADC2 Right Negative Input. PLL Loop Filter, Return to AVDD. Analog Power Supply. Connect to analog 3.3 V supply.
Rev. 0 | Page 10 of 32
AD1938 TYPICAL PERFORMANCE CHARACTERISTICS
0.10 0.08 0.06 MAGNITUDE (dB) 0.04 MAGNITUDE (dB) 0.02 0 -0.02 -0.04 -0.06 -0.08 -0.10 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 FREQUENCY (Hz)
05582-002 05582-005
0
-50
-100
-150
0
12
24 FREQUENCY (kHz)
36
48
Figure 3. ADC Pass-Band Filter Response, 48 kHz
0 -10 -20
0.05 0.10
Figure 6. DAC Stop-Band Filter Response, 48 kHz
-30
MAGNITUDE (dB)
-40 -50 -60 -70 -80 -90 -100 0 5000 10000 15000 20000 25000 30000 35000 40000 FREQUENCY (Hz)
05582-003
MAGNITUDE (dB)
0
-0.05
05582-006
-0.10
0
24
48 FREQUENCY (kHz)
72
96
Figure 4. ADC Stop-Band Filter Response, 48 kHz
0.06
Figure 7. DAC Pass-Band Filter Response, 96 kHz
0
0.04
MAGNITUDE (dB)
0.02
MAGNITUDE (dB)
-50
0
-0.02
-100
05582-004
-0.06
-150
0
8
16 FREQUENCY (kHz)
24
0
24
48 FREQUENCY (kHz)
72
96
Figure 5. DAC Pass-Band Filter Response, 48 kHz
Figure 8. DAC Stop-Band Filter Response, 96 kHz
Rev. 0 | Page 11 of 32
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-0.04
AD1938
0.5 0.4 0.3 -2 0
MAGNITUDE (dB)
0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 8 16 32 64
05582-008
MAGNITUDE (dB)
0.2
-4
-6
-8
05582-009
-10 48
64
80
96
FREQUENCY (kHz)
FREQUENCY (kHz)
Figure 9. DAC Pass-Band Filter Response, 192 kHz
Figure 10. DAC Stop-Band Filter Response, 192 kHz
Rev. 0 | Page 12 of 32
AD1938 THEORY OF OPERATION
ANALOG-TO-DIGITAL CONVERTERS (ADCS)
There are four analog-to-digital converter (ADC) channels in the AD1938 configured as two stereo pairs with differential inputs. The ADCs can operate at a nominal sample rate of 48 kHz, 96 kHz, or 192 kHz. The ADCs include on-board digital antialiasing filters with 79 dB stop-band attenuation and linear phase response, operating at an oversampling ratio of 128 (48 kHz, 96 kHz, and 192 kHz modes). Digital outputs are supplied through two serial data output pins (one for each stereo pair) and a common frame (ALRCLK) and bit (ABCLK) clock. Alternatively, one of the TDM modes can be used to access up to 16 channels on a single TDM data line. The ADCs must be driven from a differential signal source for best performance. The input pins of the ADCs connect to internal switched capacitors. To isolate the external driving op amp from the glitches caused by the internal switched capacitors, each input pin should be isolated by using a series connected, external, 100 resistor together with a 1 nF capacitor connected from each input to ground. This capacitor must be of high quality, for example, ceramic NPO or polypropylene film. The differential inputs have a nominal common-mode voltage of 1.5 V. The voltage at the common-mode reference pin (CM) can be used to bias external op amps to buffer the input signals (see the Power Supply and Voltage Reference section). The inputs can also be ac-coupled and do not need an external dc bias to CM. A digital high-pass filter can be switched in line with the ADCs under serial control to remove residual dc offsets. It has a 1.4 Hz, 6 dB per octave cutoff at a 48 kHz sample rate. The cutoff frequency scales directly with sample frequency. high frequency noise and tones to fold down into the audio band; therefore, exercise care in selecting these components. The voltage at CM, the common-mode reference pin, can be used to bias the external op amps that buffer the output signals (see the Power Supply and Voltage Reference section).
CLOCK SIGNALS
The on-chip phase locked loop (PLL) can be selected to reference the input sample rate from either of the LRCLK pins or 256, 384, 512, or 768 times the sample rate, referenced to the 48 kHz mode from the MCLKI pin. The default at power-up is 256 x fS from MCLKI. In 96 kHz mode, the master clock frequency stays at the same absolute frequency; therefore, the actual multiplication rate is divided by 2. In 192 kHz mode, the actual multiplication rate is divided by 4. For example, if a device in the AD193x family is programmed in 256 x fS mode, the frequency of the master clock input is 256 x 48 kHz = 12.288 MHz. If the AD193x is then switched to 96 kHz operation (by writing to the SPI or I2C port), the frequency of the master clock should remain at 12.288 MHz, which is now 128 x fS. In 192 kHz mode, this becomes 64 x fS. The internal clock for the ADCs is 256 x fS for all clock modes. The internal clock for the DACs varies by mode: 512 x fS (48 kHz mode), 256 x fS (96 kHz mode), or 128 x fS (192 kHz mode). By default, the on-board PLL generates this internal master clock from an external clock. A direct 512 x fS (referenced to 48 kHz mode) master clock can be used for either the ADCs or DACs if selected in PLL and Clock Control Register 1. Note that it is not possible to use a direct clock for the ADCs set to the 192 kHz mode. It is required that the on-chip PLL be used in this mode. The PLL can be powered down in PLL and Clock Control Register 0. To ensure reliable locking when changing PLL modes, or if the reference clock is unstable at power-on, power down the PLL and then power it back up when the reference clock has stabilized. The internal master clock (MCLK) can be disabled in PLL and Clock Control Register 0 to reduce power dissipation when the AD1938 is idle. The clock should be stable before it is enabled. Unless a standalone mode is selected (see the Serial Control Port section), the clock is disabled by reset and must be enabled by writing to the SPI or I2C port for normal operation. To maintain the highest performance possible, it is recommended that the clock jitter of the internal master clock signal be limited to less than 300 ps rms TIE (time interval error). Even at these levels, extra noise or tones can appear in the DAC outputs if the jitter spectrum contains large spectral peaks. If the internal PLL is not being used, it is highly recommended that an independent crystal oscillator generate the master clock. In addition, it is
DIGITAL-TO-ANALOG CONVERTERS (DACS)
The AD1938 digital-to-analog converter (DAC) channels are arranged as single-ended, four stereo pairs giving eight analog outputs for minimum external components. The DACs include on-board digital reconstruction filters with 70 dB stop band attenuation and linear phase response, operating at an oversampling ratio of 4 (48 kHz or 96 kHz modes) or 2 (192 kHz mode). Each channel has its own independently programmable attenuator, adjustable in 255 steps in increments of 0.375 dB. Digital inputs are supplied through four serial data input pins (one for each stereo pair) and a common frame (DLRCLK) and bit (DBCLK) clock. Alternatively, one of the TDM modes can be used to access up to 16 channels on a single TDM data line. Each output pin has a nominal common-mode dc level of 1.5 V and swings 1.27 V for a 0 dBFS digital input signal. A single op amp, third-order, external, low-pass filter is recommended to remove high frequency noise present on the output pins. The use of op amps with low slew rate or low bandwidth can cause
Rev. 0 | Page 13 of 32
AD1938
especially important that the clock signal should not be passed through an FPGA, CPLD, or other large digital chip (such as a DSP) before being applied to the AD1938. In most cases, this induces clock jitter due to the sharing of common power and ground connections with other unrelated digital output signals. When the PLL is used, jitter in the reference clock is attenuated above a certain frequency depending on the loop filter.
SERIAL CONTROL PORT
The AD1938 has an SPI control port that permits programming and reading back of the internal control registers for the ADCs, DACs, and clock system. There is also a standalone mode available for operation without serial control that is configured at reset using the serial control pins. All registers are set to default, except the internal MCLK enable is set to 1 and ADC BCLK and LRCLK master/slave is set by COUT/SDA. Refer to Table 11 for details. It is recommended to use a weak pull-up resistor on CLATCH in applications that have a microcontroller. This pull-up resistor ensures that the AD1938 recognizes the presence of a microcontroller. The SPI control port of the AD1938 is a 4-wire serial control port. The format is similar to the Motorola SPI format except the input data-word is 24 bits wide. The serial bit clock and latch can be completely asynchronous to the sample rate of the ADCs and DACs. Figure 11 shows the format of the SPI signal. The first byte is a global address with a read/write bit. For the AD1938 the address is 0x04, shifted left 1 bit due to the R/W bit. The second byte is the AD1938 register address and the third byte is the data.
RESET AND POWER-DOWN
Reset sets all the control registers to their default settings. To avoid pops, reset does not power down the analog outputs. After reset is deasserted, and the PLL acquires lock condition, an initialization routine runs inside the AD1938. This initialization lasts for approximately 256 MCLKs. The power-down bits in the PLL and Clock Control 0, DAC Control 1, and ADC Control 1 registers power down the respective sections. All other register settings are retained. The reset pin should be pulled low by an external resistor to guarantee proper startup.
Table 11. Stand Alone Mode Selection
ADC Clocks Slave Master
tCLS
CLATCH
CIN/ADR0 0 0
COUT/SDA 0 1
CCLK/SCL 0 0
CLATCH/ADR1 0 0
tCLH tCOTS
tCCP
tCCH tCCL
CCLK
tCDS tCDH
CIN D23 D22 D9 D8 D0
COUT
tCOE tCOD
D9
D8
D0
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Figure 11. Format of SPI Signal
Rev. 0 | Page 14 of 32
AD1938
POWER SUPPLY AND VOLTAGE REFERENCE
The AD1938 is designed for 3.3 V supplies. Separate power supply pins are provided for the analog and digital sections. These pins should be bypassed with 100 nF ceramic chip capacitors, as close to the pins as possible, to minimize noise pickup. A bulk aluminum electrolytic capacitor of at least 22 F should also be provided on the same PC board as the codec. For critical applications, improved performance is obtained with separate supplies for the analog and digital sections. If this is not possible, it is recommended that the analog and digital supplies be isolated by means of a ferrite bead in series with each supply. It is important that the analog supply be as clean as possible. All digital inputs are compatible with TTL and CMOS levels. All outputs are driven from the 3.3 V DVDD supply and are compatible with TTL and 3.3 V CMOS levels. The ADC and DAC internal voltage reference (VREF) is brought out on FILTR and should be bypassed as close as possible to the chip, with a parallel combination of 10 F and 100 nF. Any external current drawn should be limited to less than 50 A. The internal reference can be disabled in PLL and Clock Control Register 1 and FILTR can be driven from an external source. This can be used to scale the DAC output to the clipping level of a power amplifier based on its power supply voltage. The ADC input gain varies by the inverse ratio. The total gain from ADC input to DAC output remains constant. The CM pin is the internal common-mode reference. It should be bypassed as close as possible to the chip, with a parallel combination of 47 F and 100 nF. This voltage can be used to bias external op amps to the common-mode voltage of the input and output signal pins. The output current should be limited to less than 0.5 mA source and 2 mA sink. to become the bus masters according to DAC Control Register 1 and ADC Control Register 2. By default, both ADC and DAC serial ports are in the slave mode.
TIME-DIVISION MULTIPLEXED (TDM) MODES
The AD1938 serial ports also have several different TDM serial data modes. The first and most commonly used configurations are shown in Figure 12 and Figure 13. In Figure 12, the ADC serial port outputs one data stream consisting of four on-chip ADCs followed by four unused slots. In Figure 13, the eight on-chip DAC data slots are packed into one TDM stream. In this mode, both DBCLK and ABCLK are 256 fS. The I/O pins of the serial ports are defined according to the serial mode selected. For a detailed description of the function of each pin in TDM and Aux Modes, see Table 12. The AD1938 allows systems with more than eight DAC channels to be easily configured by the use of an auxiliary serial data port. The DAC TDM-AUX mode is shown in Figure 14. In this mode, the AUX channels are the last four slots of the TDM data stream. These slots are extracted and output to the AUX serial port. It should be noted that due to the high DBCLK frequency, this mode is available only in the 48 kHz/44.1 kHz/32 kHz sample rate. The AD1938 also allows system configurations with more than four ADC channels as shown in Figure 15 and Figure 16 that show using 8 ADCs and 16 ADCs, respectively. Again, due to the high ABCLK frequency, this mode is available only in the 48 kHz/44.1 kHz/32 kHz sample rate. Combining the AUX ADC and DAC modes results in a system configuration of 8 ADCs and 12 DACs. The system, then, consists of two external stereo ADCs, two external stereo DACs, and one AD1938. This mode is shown in Figure 17 (combined AUX ADC and DAC modes).
LRCLK 256 BCLKs BCLK 32 BCLKs SLOT 1 LEFT 1 SLOT 2 RIGHT 1 SLOT 3 LEFT 2 SLOT 4 RIGHT 2 SLOT 5 SLOT 6 SLOT 7 SLOT 8
SERIAL DATA PORTS--DATA FORMAT
The eight DAC channels use a common serial bit clock (DBCLK) and a common left-right framing clock (DLRCLK) in the serial data port. The four ADC channels use a common serial bit clock (ABCLK) and left-right framing clock (ALRCLK) in the serial data port. The clock signals are all synchronous with the sample rate. The normal stereo serial modes are shown in Figure 23. The ADC and DAC serial data modes default to I2S. The ports can also be programmed for left-justified, right-justified, and TDM modes. The word width is 24 bits by default and can be programmed for 16 or 20 bits. The DAC serial formats are programmable according to DAC Control Register 0. The polarity of the DBCLK and DLRCLK is programmable according to DAC Control Register 1. The ADC serial formats and serial clock polarity are programmable according to ADC Control Register 1. Both DAC and ADC serial ports are programmable
DATA
LRCLK BCLK MSB MSB-1 MSB-2 DATA
05582-016
Figure 12. ADC TDM (8-Channel I2S Mode)
LRCLK 256 BCLKs BCLK 32 BCLK SLOT 1 LEFT 1 SLOT 2 RIGHT 1 SLOT 3 LEFT 2 SLOT 4 RIGHT 2 SLOT 5 LEFT 3 SLOT 6 RIGHT 3 SLOT 7 LEFT 4 SLOT 8 RIGHT 4
DATA
LRCLK BCLK MSB MSB-1 MSB-2 DATA
05582-017
Figure 13. DAC TDM (8-Channel I2S Mode)
Rev. 0 | Page 15 of 32
AD1938
Table 12. Pin Function Changes in TDM and AUX Modes
Mnemonic ASDATA1 ASDATA2 DSDATA1 DSDATA2 DSDATA3 DSDATA4 ALRCLK ABCLK DLRCLK DBCLK Stereo Modes ADC1 Data Out ADC2 Data Out DAC1 Data In DAC2 Data In DAC3 Data In DAC4 Data In ADC LRCLK In/Out ADC BCLK In/Out DAC LRCLK In/Out DAC BCLK In/Out TDM Modes ADC TDM Data Out ADC TDM Data In DAC TDM Data In DAC TDM Data Out DAC TDM Data In 2 (Dual-Line Mode) DAC TDM Data Out 2 (Dual-Line Mode) ADC TDM Frame Sync In/Out ADC TDM BCLK In/Out DAC TDM Frame Sync In/Out DAC TDM BCLK In/Out AUX Modes TDM Data Out AUX Data Out 1 (to Ext. DAC 1) TDM Data In AUX Data In 1 (from Ext. ADC 1) AUX Data In 2 (from Ext. ADC 2) AUX Data Out 2 (to Ext. DAC 2) TDM Frame Sync In/Out TDM BCLK In/Out AUX LRCLK In/Out AUX BCLK In/Out
ALRCLK
ABCLK AUXILIARY DAC CHANNELS WILL APPEAR AT AUX DAC PORTS
DAC L4 DAC R4 AUX L1 AUX R1 AUX L2 AUX R2
DSDATA1 (TDM_IN)
UNUSED SLOTS
EMPTY EMPTY EMPTY EMPTY DAC L1 DAC R1
8-ON-CHIP DAC CHANNELS
DAC L2 DAC R2 DAC L3 DAC R3
32 BITS
MSB
DLRCLK (AUX PORT) DBCLK (AUX PORT) ASDATA2 (AUX1_OUT) DSDATA4 (AUX2_OUT)
LEFT
RIGHT
MSB
MSB
05582-051
MSB
MSB
Figure 14. 16-Channel AUX DAC Mode
Rev. 0 | Page 16 of 32
AD1938
ALRCLK
ABCLK 8-ON-CHIP DAC CHANNELS DSDATA1 (TDM_IN) DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4
4-ON-CHIP ADC CHANNELS ASDATA1 (TDM_OUT) ADC L1 ADC R1 ADC L2 ADC R2 AUX L1
4-AUX ADC CHANNELS AUX R1 AUX L2 AUX R2
32 BITS
MSB
DLRCLK (AUX PORT) DBCLK (AUX PORT) DSDATA2 (AUX1_IN) DSDATA3 (AUX2_IN)
LEFT
RIGHT
MSB
MSB
05582-050
MSB
MSB
Figure 15. 8-Channel AUX ADC Mode
ALRCLK
ABCLK
ASDATA1 (TDM_OUT)
4-ON-CHIP ADC CHANNELS
ADC L1 ADC R1 ADC L2
AUXILIARY ADC CHANNELS
AUX R1 AUX L2
UNUSED SLOTS
ADC R2 AUX L1
AUX R2 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
32 BITS
MSB
DLRCLK (AUX PORT) DBCLK (AUX PORT) DSDATA2 (AUX1_IN) DSDATA3 (AUX2_IN)
LEFT
RIGHT
MSB
MSB
05582-052
MSB
MSB
Figure 16. 16-Channel AUX ADC Mode
Rev. 0 | Page 17 of 32
AD1938
ALRCLK
ABCLK AUXILIARY DAC CHANNELS WILL APPEAR AT AUX DAC PORTS
DAC L4 DAC R4 AUX L1 AUX R1 AUX L2 AUX R2
DSDATA1 (TDM_IN)
UNUSED SLOTS
EMPTY EMPTY EMPTY EMPTY DAC L1 DAC R1
8-ON-CHIP DAC CHANNELS
DAC L2 DAC R2 DAC L3 DAC R3
ASDATA1 (TDM_OUT) DLRCLK (AUX PORT) DBCLK (AUX PORT) DSDATA2 (AUX1_IN) DSDATA3 (AUX2_IN) ASDATA2 (AUX1_OUT) DSDATA4 (AUX2_OUT)
4-ON-CHIP ADC CHANNELS
ADC L1 ADC R1 ADC L2 ADC R2
AUXILIARY ADC CHANNELS
AUX L1 AUX R1 AUX L2
UNUSED SLOTS
AUX R2 UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
LEFT
RIGHT
MSB
MSB
MSB
MSB
MSB
MSB
05582-053
MSB
MSB
Figure 17. Combined AUX DAC and ADC Mode
Rev. 0 | Page 18 of 32
AD1938
DAISY-CHAIN MODE
The AD1938 also allows a daisy-chain configuration to expand the system to 8 ADCs and 16 DACs (see Figure 18). In this mode, the DBCLK frequency is 512 fS. The first eight slots of the DAC TDM data stream belong to the first AD1938 in the chain and the last eight slots belong to the second AD1938. The second AD1938 is the device attached to the DSP TDM port. To accommodate 16 channels at a 96 kHz sample rate, the AD1938 can be configured into a dual-line, TDM mode as shown in Figure 19. This mode allows a slower DBCLK than normally required by the one-line TDM mode. Again, the first four channels of each TDM input belong to the first AD1938 in the chain and the last four channels belong to the second AD1938. The dual-line TDM mode can also be used to send data at a 192 kHz sample rate into the AD1938 as shown in Figure 20.
DLRCLK
There are two configurations for the ADC port to work in daisy-chain mode. The first one is with an ABCLK at 256 fS shown in Figure 21. The second configuration is shown in Figure 22. Note that in the 512 fS ABCLK mode, the ADC channels occupy the first eight slots; the second eight slots are empty. The TDM_IN of the first AD1938 must be grounded in all modes of operation. The I/O pins of the serial ports are defined according to the serial mode selected. See Table 13 for a detailed description of the function of each pin. See Figure 26 for a typical AD1938 configuration with two external stereo DACs and two external stereo ADCs. Figure 23 through Figure 25 show the serial mode formats. For maximum flexibility, the polarity of LRCLK and BCLK are programmable. In these figures, all of the clocks are shown with their normal polarity. The default mode is I2S.
DBCLK 8 DAC CHANNELS OF THE FIRST IC IN THE CHAIN DSDATA1 (TDM_IN) OF THE SECOND AD193x
DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4
8 DAC CHANNELS OF THE SECOND IC IN THE CHAIN
DAC L1 DAC R1 DAC L2 DAC R2 DAC L3 DAC R3 DAC L4 DAC R4
DSDATA2 (TDM_OUT) OF THE SECOND AD193x THIS IS THE TDM TO THE FIRST AD193x
DAC L1
DAC R1
DAC L2
DAC R2
DAC L3
DAC R3
DAC L4
DAC R4
8 UNUSED SLOTS 32 BITS
FIRST AD193x
SECOND AD193x
DSP
MSB
Figure 18. Single-Line DAC TDM Daisy-Chain Mode (Applicable to 48 kHz Sample Rate, 16-Channel, Two-AD1938 Daisy Chain)
Rev. 0 | Page 19 of 32
05582-054
AD1938
DLRCLK
DBCLK 8 DAC CHANNELS OF THE FIRST IC IN THE CHAIN DSDATA1 (IN) DSDATA2 (OUT) DSDATA3 (IN) DSDATA4 (OUT) 32 BITS DAC L3 DAC R3 DAC L4 DAC R4 DAC L1 DAC R1 DAC L2 DAC R2 8 DAC CHANNELS OF THE SECOND IC IN THE CHAIN DAC L1 DAC R1 DAC L2 DAC R2
DAC L1
DAC R1
DAC L2
DAC R2
DAC L3
DAC R3
DAC L4
DAC R4
DAC L3
DAC R3
DAC L4
DAC R4
MSB
FIRST AD193x
SECOND AD193x
DSP
Figure 19. Dual-Line DAC TDM Mode (Applicable to 96 kHz Sample Rate, 16-Channel, Two-AD1938 Daisy Chain); DSDATA3 and DSDATA4 are the Daisy Chain
DLRCLK
DBCLK
DSDATA1
DAC L1
DAC R1
DAC L2
DAC R2
DSDATA2
DAC L3
DAC R3
DAC L4
DAC R4
32 BITS
MSB
Figure 20. Dual-Line DAC TDM Mode (Applicable to 192 kHz Sample Rate, 8-Channel Mode)
ALRCLK
ABCLK 4 ADC CHANNELS OF SECOND IC IN THE CHAIN ADC L1 ADC R1 ADC L2 ADC R2 4 ADC CHANNELS OF FIRST IC IN THE CHAIN ADC L1 ADC R1 ADC L2 ADC R2
ASDATA1 (TDM_OUT OF THE SECOND AD193x IN THE CHAIN) ASDATA2 (TDM_IN OF THE SECOND AD193x IN THE CHAIN)
ADC L1
ADC R1
ADC L2
ADC R2
32 BITS FIRST AD193x SECOND AD193x DSP
05582-056
MSB
Figure 21. ADC TDM Daisy-Chain Mode (256 fS BCLK, Two AD193x Daisy Chain)
Rev. 0 | Page 20 of 32
05582-058
05582-055
AD1938
ALRCLK
ABCLK
ASDATA1 (TDM_OUT OF THE SECOND AD193x IN THE CHAIN)
4 ADC CHANNELS OF SECOND IC IN THE CHAIN
ADC L1 ADC R1 ADC L2 ADC R2
4 ADC CHANNELS OF FIRST IC IN THE CHAIN
ADC L1 ADC R1 ADC L2 ADC R2
ASDATA2 (TDM_IN OF THE SECOND AD193x IN THE CHAIN)
ADC L1
ADC R1
ADC L2
ADC R2
32 BITS
MSB
Figure 22. ADC TDM Daisy-Chain Mode (512 fS BCLK, Two AD193x Daisy Chain)
LRCLK BCLK SDATA MSB
LEFT CHANNEL
RIGHT CHANNEL
LSB
MSB
LSB
LEFT-JUSTIFIED MODE--16 BITS TO 24 BITS PER CHANNEL
LRCLK BCLK SDATA MSB
LEFT CHANNEL
RIGHT CHANNEL
LSB
MSB
LSB
I2S MODE--16 BITS TO 24 BITS PER CHANNEL
LRCLK BCLK SDATA
LEFT CHANNEL
RIGHT CHANNEL
MSB
LSB
MSB
LSB
RIGHT-JUSTIFIED MODE--SELECT NUMBER OF BITS PER CHANNEL LRCLK BCLK SDATA MSB LSB MSB LSB
DSP MODE--16 BITS TO 24 BITS PER CHANNEL 1/fS
05582-013
NOTES 1. DSP MODE DOES NOT IDENTIFY CHANNEL 2. LRCLK NORMALLY OPERATES AT fS EXCEPT FOR DSP MODE WHICH IS 2 x fS 3. BCLK FREQUENCY IS NORMALLY 64 x LRCLK BUT MAY BE OPERATED IN BURST MODE.
Figure 23. Stereo Serial Modes
Rev. 0 | Page 21 of 32
05582-057
FIRST AD193x
SECOND AD193x
DSP
AD1938
tDBH
DBCLK
tDBP tDBL tDLS tDLH
DLRCLK
DSDATA LEFT-JUSTIFIED MODE
tDDS
MSB MSB-1
tDDH
DSDATA I2C-JUSTIFIED MODE
tDDS
MSB
tDDH tDDS tDDS
LSB
05582-014 05582-015
DSDATA RIGHT-JUSTIFIED MODE
MSB
tDDH
tDDH
Figure 24. DAC Serial Timing
tABH
ABCLK
tABP
tABL tALS
ALRCLK
tALH
tABDD
ASDATA LEFT-JUSTIFIED MODE MSB MSB-1
tABDD
ASDATA I2C-JUSTIFIED MODE MSB
tABDD
ASDATA RIGHT-JUSTIFIED MODE MSB LSB
Figure 25. ADC Serial Timing
Rev. 0 | Page 22 of 32
AD1938
Table 13. Pin Function Changes in TDM and AUX Modes (Replication of Table 12)
Mnemonic ASDATA1 ASDATA2 DSDATA1 DSDATA2 DSDATA3 DSDATA4 ALRCLK ABCLK DLRCLK DBCLK Stereo Modes ADC1 Data Out ADC2 Data Out DAC1 Data In DAC2 Data In DAC3 Data In DAC4 Data In ADC LRCLK In/Out ADC BCLK In/Out DAC LRCLK In/Out DAC BCLK In/Out TDM Modes ADC TDM Data Out ADC TDM Data In DAC TDM Data In DAC TDM Data Out DAC TDM Data In 2 (Dual-Line Mode) DAC TDM Data Out 2 (Dual-Line Mode) ADC TDM Frame Sync In/Out ADC TDM BCLK In/Out DAC TDM Frame Sync In/Out DAC TDM BCLK In/Out AUX Modes TDM Data Out AUX Data Out 1 (to Ext. DAC 1) TDM Data In AUX Data In 1 (from Ext. ADC 1) AUX Data In 2 (from Ext. ADC 2) AUX Data Out 2 (to Ext. DAC 2) TDM Frame Sync In/Out TDM BCLK In/Out AUX LRCLK In/Out AUX BCLK In/Out
30MHz
FSYNC-TDM (RFS)
SHARC
SHARC IS RUNNING IN SLAVE MODE (INTERRUPT-DRIVEN)
RxDATA
LRCLK AUX ADC 1 BCLK DATA MCLK ASDATA1 ALRCLK ABCLK DSDATA1 DBCLK DLRCLK LRCLK AUX ADC 2 BCLK DATA MCLK DSDATA2 DSDATA3 MCLK
TxDATA
RxCLK
TxCLK
12.288MHz
TFS (NC)
LRCLK BCLK AUX DATA ADC 1 MCLK
AD1938
TDM MASTER AUX MASTER ASDATA2 DSDATA4
LRCLK BCLK AUX DATA ADC 2 MCLK
Figure 26. Example of AUX Mode Connection to SHARC (AD1938 as TDM Master/AUX Master Shown)
Rev. 0 | Page 23 of 32
05582-019
AD1938 CONTROL REGISTERS
DEFINITIONS
The format is the same for I2C and SPI ports. The global address for the AD1938 is 0x04, shifted left 1 bit due to the R/W bit. However, in I2C, ADR0 and ADR1 are OR'ed into Bit 17 and Bit 8 to provide multiple chip addressing. All registers are reset to 0, except for the DAC volume registers that are set to full volume. Note that the first setting in each control register parameter is the default setting. Table 14. Register Format
Global Address Bit 23:17 R/W 16 Register Address 15:8 Data 7:0
Table 15. Register Addresses and Functions
Address 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Function PLL and Clock Control 0 PLL and Clock Control 1 DAC Control 0 DAC Control 1 DAC Control 2 DAC individual channel mutes DAC 1L volume control DAC 1R volume control DAC 2L volume control DAC 2R volume control DAC 3L volume control DAC 3R volume control DAC 4L volume control DAC 4R volume control ADC Control 0 ADC Control 1 ADC Control 2
PLL AND CLOCK CONTROL REGISTERS
Table 16. PLL and Clock Control 0
Bit 0 2:1 Value 0 1 00 01 10 11 00 01 10 11 00 01 10 11 0 1 Function Normal operation Power-down INPUT 256 (x44.1 kHz or 48 kHz) INPUT 384 (x44.1 kHz or 48 kHz) INPUT 512 (x44.1 kHz or 48 kHz) INPUT 768 (x44.1 kHz or 48 kHz) XTAL oscillator enabled 256 x fS VCO output 512 x fS VCO output Off MCLK DLRCLK ALRCLK Reserved Disable: ADC and DAC idle Enable: ADC and DAC active Description PLL power-down MCLK pin functionality (PLL active)
4:3
MCLK_O pin
6:5
PLL input
7
Internal MCLK enable
Rev. 0 | Page 24 of 32
AD1938
Table 17. PLL and Clock Control 1
Bit 0 1 2 3 7:4 Value 0 1 0 1 0 1 0 1 0000 Function PLL clock MCLK PLL clock MCLK Enabled Disabled Not locked Locked Reserved Description DAC clock source select ADC clock source select On-chip voltage reference PLL lock indicator (read only)
DAC CONTROL REGISTERS
Table 18. DAC Control 0
Bit 0 2:1 Value 0 1 00 01 10 11 000 001 010 011 100 101 110 111 00 01 10 11 Function Normal Power-down 32 kHz/44.1 kHz/48 kHz 64 kHz/88.2 kHz/96 kHz 128 kHz/176.4 kHz/192 kHz Reserved 1 0 8 12 16 Reserved Reserved Reserved Stereo (normal) TDM (daisy chain) DAC AUX mode (ADC-, DAC-, TDM-coupled) Dual-line TDM Description Power-down Sample rate
5:3
SDATA delay (BCLK periods)
7:6
Serial format
Table 19. DAC Control 1
Bit 0 2:1 Value 0 1 00 01 10 11 0 1 0 1 0 1 0 1 0 1 Function Latch in mid cycle (normal) Latch in at end of cycle (pipeline) 64 (2 channels) 128 (4 channels) 256 (8 channels) 512 (16 channels) Left low Left high Slave Master Slave Master DBCLK pin Internally generated Normal Inverted Description BCLK active edge (TDM in) BCLKs per frame
3 4 5 6 7
LRCLK polarity LRCLK master/slave BCLK master/slave BCLK source BCLK polarity
Rev. 0 | Page 25 of 32
AD1938
Table 20. DAC Control 2
Bit 0 2:1 Value 0 1 00 01 10 11 00 01 10 11 0 1 00 Function Unmute Mute Flat 48 kHz curve 44.1 kHz curve 32 kHz curve 24 20 Reserved 16 Noninverted Inverted Reserved Description Master Mute Deemphasis (32 kHz/44.1 kHz/48 kHz mode only)
4:3
Word width
5 7:6
DAC output polarity
Table 21. DAC Individual Channel Mutes
Bit 0 1 2 3 4 5 6 7 Value 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Function Unmute Mute Unmute Mute Unmute Mute Unmute Mute Unmute Mute Unmute Mute Unmute Mute Unmute Mute Description DAC 1 left mute DAC 1 right mute DAC 2 left mute DAC 2 right mute DAC 3 left mute DAC 3 right mute DAC 4 left mute DAC 4 right mute
Table 22. DAC Volume Controls
Bit 7:0 Value 0 1 to 254 255 Function No attenuation -3/8 dB per step Full attenuation Description DAC volume control
Rev. 0 | Page 26 of 32
AD1938
ADC CONTROL REGISTERS
Table 23. ADC Control 0
Bit 0 1 2 3 4 5 7:6 Value 0 1 0 1 0 1 0 1 0 1 0 1 00 01 10 11 Function Normal Power down Off On Unmute Mute Unmute Mute Unmute Mute Unmute Mute 32 kHz/44.1 kHz/48 kHz 64 kHz/88.2 kHz/96 kHz 128 kHz/176.4 kHz/192 kHz Reserved Description Power-down High-pass filter ADC 1L mute ADC 1R mute ADC 2L mute ADC 2R mute Output sample rate
Table 24. ADC Control 1
Bit 1:0 Value 00 01 10 11 000 001 010 011 100 101 110 111 00 01 10 11 0 1 Function 24 20 Reserved 16 1 0 8 12 16 Reserved Reserved Reserved Stereo TDM (daisy chain) ADC Aux mode (ADC-, DAC, TDM-coupled) Reserved Latch in mid cycle (normal) Latch in at end of cycle (pipeline) Description Word width
4:2
SDATA delay (BCLK periods)
6:5
Serial format
7
BCLK active edge (TDM in)
Rev. 0 | Page 27 of 32
AD1938
Table 25. ADC Control 2
Bit 0 1 2 3 5:4 Value 0 1 0 1 0 1 0 1 00 01 10 11 0 1 0 1 Function 50/50 (allows 32-/24-/20-/16-BCLK/channel) Pulse (32-BCLK/channel) Drive out on falling edge (DEF) Drive out on rising edge Left low Left high Slave Master 64 128 256 512 Slave Master ABCLK pin Internally generated Description LRCLK format BCLK polarity LRCLK polarity LRCLK master/slave BCLKs per frame
6 7
BCLK master/slave BCLK source
Rev. 0 | Page 28 of 32
AD1938
ADDITIONAL MODES
The AD1938 offers several additional modes for board level design enhancements. To reduce the EMI in board level design, serial data can be transmitted without an explicit BCLK. See Figure 27 for an example of a DAC TDM data transmission mode that does not require high speed DBCLK. This configuration is applicable when the AD1938 master clock is generated by the PLL with the DLRCLK as the PLL reference frequency. To relax the requirement for the setup time of the AD1938 in cases of high speed TDM data transmission, the AD1938 can latch in the data using the falling of DBCLK. This effectively dedicates the entire BCLK period to the setup time. This mode is useful in cases where the source has a large delay time in the serial data driver. Figure 28 shows this pipeline mode of data transmission. Both the BLCK-less and pipeline modes are available on the ADC serial data port.
DLRCLK 32 BITS INTERNAL DBCLK
DSDATA
DLRCLK
INTERNAL DBCLK
05582-059
TDM-DSDATA
Figure 27. Serial DAC Data Transmission in TDM Format Without DBCLK (Applicable Only If PLL Locks to DLRCLK. This Mode Is Also Available in the ADC Serial Data Port)
DLRCLK
DBCLK DATA MUST BE VALID AT THIS BCLK EDGE DSDATA MSB
05582-060
Figure 28. I2S Pipeline Mode in DAC Serial Data Transmission (Applicable in Stereo and TDM Useful for High Frequency TDM Transmission This Model Is Also Available in the ADC Serial Data Port.)
Rev. 0 | Page 29 of 32
AD1938 APPLICATION CIRCUITS
Typical applications circuits are shown in Figure 29 through Figure 32. Figure 29 shows a typical ADC input filter circuit. Recommended loop filters for LR clock and master clock as the PLL reference are shown in Figure 30. Output filters for the DAC outputs are shown in Figure 31 and Figure 32 for the noninverting and inverting cases.
120pF 600Z 100pF 5.76k 2 3 - OP275 + 5.76k 1
AUDIO INPUT
240pF NPO 3 4.75k 4.75k 2 + OP275 -
DAC OUT
5.76k 120pF 4.7F 237 + 1nF NPO
1
604 4.7F + 3.3nF NPO
AUDIO OUTPUT 49.9k
ADCxN
4.99k
100pF 6 5 5.76k - OP275 + 7 1nF NPO 4.7F 237 +
05582-023
ADCxP
Figure 29. Typical ADC Input Filter Circuit
Figure 31. Typical DAC Output Filter Circuit (Single-Ended, Noninverting)
LF +
LRCLK 39nF 2.2nF 3.32k
LF
MCLK 5.6nF 390nF
05582-027
11k DAC OUT 11k 270pF NPO
68pF NPO 2 3.01k CM 0.1F 3 - OP275 + 1 604 4.7F + 2.2nF NPO AUDIO OUTPUT 49.9k
05582-025
562 AVDD2
AVDD2
Figure 30. Recommended Loop Filters for LRCLK and MCLK PLL Reference
Figure 32. Typical DAC Output Filter Circuit (Single-Ended, Inverting)
Rev. 0 | Page 30 of 32
05582-024
270pF NPO
4.99k
AD1938 OUTLINE DIMENSIONS
0.75 0.60 0.45 1.60 MAX
48 1
PIN 1
9.00 BSC SQ
37 36
1.45 1.40 1.35
TOP VIEW
0.20 0.09 7 3.5 0 0.08 MAX COPLANARITY
(PINS DOWN)
7.00 BSC SQ
0.15 0.05
12 13 24
25
SEATING PLANE
VIEW A
ROTATED 90 CCW
COMPLIANT TO JEDEC STANDARDS MS-026-BBC
VIEW A
0.50 BSC LEAD PITCH
0.27 0.22 0.17
Figure 33. 48-Lead Low Profile Quad Flat Package [LQFP] (ST-48) Dimensions shown in millimeters
ORDERING GUIDE
Model AD1938YSTZ 1, 2 AD1938YSTZRL1, 2 EVAL-AD1938EB
1 2
Temperature Range -40C to +105C -40C to +105C
Package Description 48-Lead LQFP 48-Lead LQFP, 13" Reel Evaluation Board
Package Option ST-48 ST-48
Z = Pb-free part. Single-ended output; SPI control port.
Rev. 0 | Page 31 of 32
AD1938 NOTES
(c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D05582-0-5/06(0)
Rev. 0 | Page 32 of 32

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