4 ADC with PLL,
192 kHz, 24-Bit ADC
Data Sheet
AD1974
Rev. D Document Feedback
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.
Tel: 781.329.4700 ©2007–2013 Analog Devices, Inc. All rights reserved.
Technical Support www.analog.com
FEATURES
Phase-locked loop generated or direct master clock
Low EMI design
107 dB 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
SPI®-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 input/output
Available in a 48-lead LQFP
Qualified for automotive applications
APPLICATIONS
Automotive audio systems
Home Theater Systems
Set-top boxes
Digital audio effects processors
GENERAL DESCRIPTION
The AD1974 is a high performance, single-chip ADC that pro-
vides four analog-to-digital converters (ADCs) with differential
inputs using the Analog Devices, Inc. patented multibit sigma-
delta (Σ-Δ) architecture. An SPI port is included, allowing a
microcontroller to enable mutes and adjust many other
parameters. The AD1974 operates from 3.3 V digital and analog
supplies. The AD1974 is available in a single-ended output
48-lead L Q F P.
The AD1974 is designed for low EMI. This consideration is
apparent in both the system and circuit design architectures.
By using the on-board phase-locked loop (PLL) to derive the
master clock from the LR clock or from an external crystal,
the AD1974 eliminates the need for a separate high frequency
master clock and can also be used with a suppressed bit clock.
The ADCs are designed using the latest continuous time archi-
tectures from Analog Devices to further minimize EMI. By
using 3.3 V supplies, power consumption is minimized, further
reducing emissions.
FUNCTIONAL BLOCK DIAGRAM
QUAD
DEC
FILTER
48kHz/
96kHz/192kHz
SERIAL DATA PORT
DIGITAL AUDIO
INPUT/OUTPUT
PRECISION
VOLTAGE
REFERENCE 12.48MHz
TIMI NG MANAGEM E NT
AND CONTROL
(CL OCK AND PL L)
CONTROL PORT
SPI
CONTROL DAT A
INPUT/OUTPUT
AD1974
ADC
ADC
ADC
ADC
ANALOG
AUDIO
INPUTS
SDATA
OUT
CLOCKS
06614-001
Figure 1.
AD1974 Data Sheet
Rev. D | Page 2 of 24
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........................................... 4
Power Supply Specifications........................................................ 5
Digital Filters ................................................................................. 5
Timing Specifications .................................................................. 5
Absolute Maximum Ratings ............................................................ 7
Thermal Resistance ...................................................................... 7
ESD Caution .................................................................................. 7
Pin Configuration and Function Descriptions ............................. 8
Typical Performance Characteristics ........................................... 10
Theory of Operation ...................................................................... 11
Analog-to-Digital Converters (ADCs) .................................... 11
Clock Signals ............................................................................... 11
Reset and Power-Down ............................................................. 11
Serial Control Port ..................................................................... 12
Power Supply and Voltage Reference ....................................... 12
Serial Data Ports—Data Format ............................................... 12
TDM Modes ................................................................................ 13
Daisy-Chain Mode ..................................................................... 14
Control Registers ............................................................................ 18
PLL and Clock Control Registers ............................................. 18
AUXPORT Control Registers ................................................... 19
ADC Control Registers .............................................................. 20
Additional Modes ....................................................................... 21
Application Circuits ....................................................................... 23
Outline Dimensions ....................................................................... 24
Ordering Guide .......................................................................... 24
Automotive Products ................................................................. 24
REVISION HISTORY
3/13—Rev. C to Rev. B
Change to tCLH Parameter, Table 7 ................................................... 6
Changes to Serial Control Port Section ........................................ 12
2/11—Rev. B to Rev. C
Changes to Features Section............................................................ 1
Changes to Ordering Guide .......................................................... 24
Added Automotive Products Section .......................................... 24
6/10—Rev. A to Rev. B
Changed 130°C to 125°C Throughout ........................................... 4
Changed TA to TC Throughout ....................................................... 4
Changes to Endnote 2 in Ordering Guide .................................. 24
11/09—Rev. 0 to Rev. A
Changed Codec to ADC ............................................... Throughout
Changes to Features and General Description Sections .............. 1
Changes to Clock Signals Section ................................................ 11
Changes to Figure 12 and Figure 13 ............................................ 16
Changes to Control Registers Section ......................................... 18
4/07—Revision 0: Initial Version
Data Sheet AD1974
Rev. D | Page 3 of 24
SPECIFICATIONS
TEST CONDITIONS
Performance of all channels is identical, exclusive of the interchannel gain mismatch and interchannel phase deviation specifications.
Supply Voltages (AVDD, DVDD) 3.3 V
Temperature Range1 As specified in Table 1 and Table 2
Master Clock 12.288 MHz (48 kHz fS, 256 × fS mode)
Input Sample Rate 48 kHz
Measurement Bandwidth 20 Hz to 20 kHz
Word Width 24 bits
Load Capacitance (Digital Output) 20 pF
Load Current (Digital Output) ±1 mA or 1.5 kΩ to ½ DVDD supply
Input Voltage High 2.0 V
Input Voltage Low 0.8 V
1 Functionally guaranteed at −40°C to +125°C case temperature.
ANALOG PERFORMANCE SPECIFICATIONS
Specifications guaranteed at 25°C (ambient).
Table 1.
Parameter Conditions Min Typ Max Unit
ANALOG-TO-DIGITAL CONVERTERS
ADC Resolution All ADCs 24 Bits
Full-Scale Input Voltage (Differential) 1.9 V rms
Dynamic Range 20 Hz to 20 kHz, −60 dB input
No Filter (RMS) 98 102 dB
With A-Weighted Filter (RMS) 100 105 dB
Total Harmonic Distortion + Noise (THD + N) −1 dBFS −96 −87 dB
Gain Error −10 +10 %
Interchannel Gain Mismatch
−0.25
+0.25
dB
Offset Error −10 0 +10 mV
Gain Drift 100 ppm/°C
Interchannel Isolation −110 dB
CMRR 100 mV rms, 1 kHz 55 dB
100 mV rms, 20 kHz 55 dB
Input Resistance 14 kΩ
Input Capacitance 10 pF
Input Common-Mode Bias Voltage 1.5 V
REFERENCE
Internal Reference Voltage FILTR pin 1.50 V
External Reference Voltage FILTR pin 1.32 1.50 1.68 V
Common-Mode Reference Output CM pin 1.50 V
AD1974 Data Sheet
Rev. D | Page 4 of 24
Specifications measured at 125°C (case).
Table 2.
Parameter Conditions Min Typ Max Unit
ANALOG-TO-DIGITAL CONVERTERS
ADC Resolution All ADCs 24 Bits
Full-Scale Input Voltage (Differential) 1.9 V rms
Dynamic Range
20 Hz to 20 kHz, −60 dB input
No Filter (RMS) 95 102 dB
With A-Weighted Filter (RMS) 97 105 dB
Total Harmonic Distortion + Noise (THD + N) −1 dBFS −96 −87 dB
Gain Error −10 +10 %
Interchannel Gain Mismatch
−0.25
+0.25
dB
Offset Error −10 0 +10 mV
REFERENCE
Internal Reference Voltage FILTR pin 1.50 V
External Reference Voltage FILTR pin 1.32 1.50 1.68 V
Common-Mode Reference Output CM pin 1.50 V
CRYSTAL OSCILLATOR SPECIFICATIONS
Table 3.
Parameter Min Typ Max Unit
Transconductance 3.5 Mmhos
DIGITAL INPUT/OUTPUT SPECIFICATIONS
−40°C < TC < +125°C, DVDD = 3.3 V ± 10%.
Table 4.
Parameter Conditions/Comments Min Typ Max Unit
Input Voltage High (VIH) 2.0 V
Input Voltage High (VIH) MCLKI pin 2.2 V
Input Voltage Low (VIL) 0.8 V
Input Leakage IIH @ VIH = 2.4 V 10 µA
IIL @ VIL = 0.8 V 10 µA
High Level Output Voltage (VOH) IOH = 1 mA DVDD − 0.60 V
Low Level Output Voltage (VOL) IOL = 1 mA 0.4 V
Input Capacitance 5 pF
Data Sheet AD1974
Rev. D | Page 5 of 24
POWER SUPPLY SPECIFICATIONS
Table 5.
Parameter Conditions/Comments Min Typ Max Unit
SUPPLIES
Voltage
DVDD 3.0 3.3 3.6 V
AVDD 3.0 3.3 3.6 V
Digital Current MCLK = 256 fS
Normal Operation fS = 48 kHz 56 mA
fS = 96 kHz 65 mA
fS = 192 kHz 95 mA
Power-Down fS = 48 kHz to 192 kHz 2.0 mA
Analog Current
Normal Operation 74 mA
Power-Down 23 mA
DISSIPATION
Operation MCLK = 256 fS, 48 kHz
All Supplies
429
mW
Digital Supply 185 mW
Analog Supply 244 mW
Power-Down, All Supplies 83 mW
POWER SUPPLY REJECTION RATIO
Signal at Analog Supply Pins 1 kHz, 200 mV p-p 50 dB
20 kHz, 200 mV p-p 50 dB
DIGITAL FILTERS
Table 6.
Parameter Mode Factor Min Typ Max Unit
ADC DECIMATION FILTER All modes @ 48 kHz
Pass Band 0.4375 fS 21 kHz
Pass-Band Ripple ±0.015 dB
Transition Band 0.5 fS 24 kHz
Stop Band 0.5625 fS 27 kHz
Stop-Band Attenuation 79 dB
Group Delay 22.9844 fS 479 µs
TIMING SPECIFICATIONS
−40°C < TC < +125°C, DVDD = 3.3 V ± 10%.
Table 7.
Parameter Condition Comments Min Max Unit
INPUT MASTER CLOCK (MCLK)
AND RESET
tMH MCLK duty cycle ADC clock source = PLL clock @ 256 fS, 384 fS, 512 fS, 768 fS 40 60 %
tMH ADC clock source = direct MCLK @ 512 fS (bypass
on-chip PLL)
40 60 %
f
MCLK
MCLK frequency
PLL mode, 256 f
S
reference
6.9
13.8
MHz
fMCLK Direct 512 fS mode 27.6 MHz
tPDR Low 15 ns
tPDRR Recovery Reset to active output 4096 tMCLK
AD1974 Data Sheet
Rev. D | Page 6 of 24
Parameter Condition Comments Min Max Unit
PLL
Lock Time MCLK and LRCLK input 10 ms
256 fS VCO Clock 40 60 %
Output Duty Cycle
MCLK_O Pin
SPI PORT See Figure 5
tCCH CCLK high 35 ns
tCCL CCLK low 35 ns
fCCLK CCLK frequency fCCLK = 1/tCCP; only tCCP shown in Figure 5
10 MHz
tCDS CDATA setup To CCLK rising 10 ns
tCDH CDATA hold From CCLK rising 10 ns
tCLS Setup To CCLK rising 10 ns
tCLH Hold From CCLK rising 10 ns
tCLHIGH High Not shown in Figure 5 10 ns
tCOE COUT enable From CCLK falling 30 ns
tCOD COUT delay From CCLK falling 30 ns
tCOH COUT hold From CCLK falling, not shown in Figure 5 30 ns
tCOTS COUT tristate From CCLK falling 30 ns
ADC SERIAL PORT See Figure 13
tABH ABCLK high Slave mode 10 ns
tABL ABCLK low Slave mode 10 ns
t
ALS
ALRCLK setup
To ABCLK rising, slave mode
10
ns
tALH ALRCLK hold From ABCLK rising, slave mode 5 ns
tALS ALRCLK skew From ABCLK falling, master mode −8 +8 ns
tABDD ASDATA delay From ABCLK falling 18 ns
AUXILIARY INTERFACE See Figure 12
tXDS AAUXDATA setup To AUXBCLK rising 10 ns
tXDH AAUXDATA hold From AUXBCLK rising 5 ns
tXBH AUXBCLK high 10 ns
tXBL AUXBCLK low 10 ns
t
XLS
AUXLRCLK setup
To AUXBCLK rising
10
ns
tXLH AUXLRCLK hold From AUXBCLK rising 5 ns
Data Sheet AD1974
Rev. D | Page 7 of 24
ABSOLUTE MAXIMUM RATINGS
Table 8.
Parameter Rating
Analog (AVDD) −0.3 V to +3.6 V
Digital (DVDD) −0.3 V to +3.6 V
Input Current (Except Supply Pins) ±20 mA
Analog Input Voltage (Signal Pins) –0.3 V to AVDD + 0.3 V
Digital Input Voltage (Signal Pins) −0.3 V to DVDD + 0.3 V
Operating Temperature Range (Case) −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Stresses above those listed under 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.
THERMAL RESISTANCE
θJA represents thermal resistance, junction-to-ambient; θJC
represents the thermal resistance, junction-to-case. All
characteristics are for a 4-layer board.
Table 9.
Package Type θJA θJC Unit
48-Lead LQFP 50.1 17 °C/W
ESD CAUTION
AD1974 Data Sheet
Rev. D | Page 8 of 24
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AVDD
48
LF
47
ADC2RN
46
ADC2RP
45
ADC2LN
44
ADC2LP
43
ADC1RN
42
ADC1RP
41
ADC1LN
40
ADC1LP
39
CM
38
AVDD
37
DVDD
13
AUXDATA2
14
AUXDATA1
15
NC
16
AUXBCLK
17
AUXLRCLK
18
ASDATA2
19
ASDATA1
20
ABCLK
21
ALRCLK
22
CIN
23
COUT
24
AGND 1
MCLKI/XI 2
MCLKO/XO 3
AGND 4
AVDD 5
NC 6
NC 7
NC
NC = NO CONNECT
8
NC 9
PD/RST 10
NC 11
DGND 12
AGND
36
FILTR
35
AGND
34
AVDD
33
AGND
32
NC
31
NC
30
NC
29
NC
28
CLATCH
27
CCLK
26
DGND
25
AD1974
TOP VI EW
(No t t o Scal e)
SINGLE-ENDED
OUTPUT
06614-020
Figure 2. AD1974 Single-Ended Output, 48-Lead LQFP Pin Configuration
Table 10. Pin Function Description
Pin No.
Type
1
Mnemonic
Description
1, 4, 32, 34, 36 I AGND Analog Ground.
2 I MCLKI/XI Master Clock Input/Crystal Oscillator Input.
3 O MCLKO/XO Master Clock Output/Crystal Oscillator Output.
5, 33, 37, 48 I AVDD Analog Power Supply. Connect to analog 3.3 V supply.
6 to 9, 11, 16, 28 to 31 NC No Connect.
10 I PD/
RST Power-Down/Reset (Active Low).
12, 25
I
DGND
Digital Ground.
13
I
DVDD
Digital Power Supply. Connect to digital 3.3 V supply.
14 I/O AUXDATA2 Auxiliary Data Input 2 (From External ADC 2).
15 I/O AUXDATA1 Auxiliary Data Input 1 (From External ADC 1).
17 I/O AUXBCLK Auxiliary Bit Clock.
18 I/O AUXLRCLK Auxiliary Left-Right Framing Clock.
19 I/O ASDATA2 ADC Serial Data Output 2 (ADC 2 Left and ADC 2 Right)/ADC TDM Data Input.
20 O ASDATA1 ADC Serial Data Output 1 (ADC 1 Left and ADC 1 Right)/ADC TDM Data Output.
21 I/O ABCLK Serial Bit Clock for ADCs.
22 I/O ALRCLK Left-Right Framing Clock for ADCs.
23 I CIN Control Data Input (SPI).
24
I/O
COUT
Control Data Output (SPI).
26 I CCLK Control Clock Input (SPI).
27 I CLATCH Latch Input for Control Data (SPI).
35 O FILTR Voltage Reference Filter Capacitor Connection. Bypass with 10 µF||100 nF to AGND.
38 O CM Common-Mode Reference Filter Capacitor Connection. Bypass with 47 µF||100 nF to AGND.
39 I ADC1LP ADC1 Left Positive Input.
40 I ADC1LN ADC1 Left Negative Input.
41 I ADC1RP ADC1 Right Positive Input.
42 I ADC1RN ADC1 Right Negative Input.
43 I ADC2LP ADC2 Left Positive Input.
Data Sheet AD1974
Rev. D | Page 9 of 24
Pin No. Type 1 Mnemonic Description
44 I ADC2LN ADC2 Left Negative Input.
45 I ADC2RP ADC2 Right Positive Input.
46 I ADC2RN ADC2 Right Negative Input.
47 O LF PLL Loop Filter, Return to AVDD.
1 I = input, O = output.
AD1974 Data Sheet
Rev. D | Page 10 of 24
TYPICAL PERFORMANCE CHARACTERISTICS
0.10
0.08
0.06
0.04
0.02
0
–0.10
–0.08
–0.06
–0.04
–0.02
01800016000
1400012000100008000600040002000
MAG NITUDE ( dB)
FRE QUENCY ( kHz )
06614-002
Figure 3. ADC Pass-Band Filter Response, 48 kHz
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100 040000
5000 10000 15000 20000 25000 30000 35000
MAG NITUDE ( dB)
FRE QUENCY ( kHz )
06614-003
Figure 4. ADC Stop-Band Filter Response, 48 kHz
Data Sheet AD1974
Rev. D | Page 11 of 24
THEORY OF OPERATION
ANALOG-TO-DIGITAL CONVERTERS (ADCS)
There are four ADC channels in the AD1974 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 a 79 dB stop-
band attenuation and a 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) as well as a common
frame (ALRCLK) and bit clock (ABCLK). Alternatively, one
of the time division multiplexed (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 inter-
nal 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 Ω resistor together with a 1 nF capacitor connected
from each input to ground. This capacitor must be of high quality,
for instance, a ceramic NP0 capacitor or a polypropylene film
capacitor.
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 fre-
quency scales directly with sample frequency.
The voltage at CM 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 PLL can be selected to reference the input sample
rate from either the LRCLK or AUXLRCK pins or 256, 384, 512,
or 768 times the sample rate, referenced to the 48 kHz mode from
the MCLKI/XI pin. The default at power-up is 256 × fS from
MCLKI. In 96 kHz mode, the master clock frequency stays
at the same absolute frequency; therefore, the actual mul-
tiplication rate is divided by 2. In 192 kHz mode, the actual
multiplication rate is divided by 4. For example, if the AD1974
is programmed in 256 × fS mode, the frequency of the master
clock input is 256 × 48 kHz = 12.288 MHz. If the AD1974 is
then switched to 96 kHz operation (by writing to the SPI
port), the frequency of the master clock should remain at
12.288 MHz (128 × fS). In 192 kHz mode, this becomes 64 × fS.
The internal clock for the ADCs is 256 × fS for all clock modes.
By default, the on-board PLL generates this internal master clock
from an external clock. A direct 512 × fS (referenced to 48 kHz
mode) master clock can be used for the ADCs if selected in the
PLL and Clock Control 1 register.
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 the PLL and Clock Control 0
register. 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 MCLK can be disabled in the PLL and Clock Control
0 register to reduce power dissipation when the AD1974 is idle.
The clock should be stable before it is enabled. Unless a stand-
alone mode is selected (see the Serial Control Port section), the
clock is disabled by reset and must be enabled by writing to the
SPI port for normal operation.
To maintain the highest performance possible, it is recom-
mended that the clock jitter of the internal master clock signal
be limited to less than 300 ps rms time interval error (TIE). Even
at these levels, extra noise or tones can appear in the outputs if
the jitter spectrum contains large spectral peaks. If the internal
PLL is not being used, it is highly recommended that an inde-
pendent crystal oscillator generate the master clock. In addition,
it is especially important that the clock signal should not be
passed through an FPGA, CPLD, DSP, or other large digital
chip before being applied to the AD1974. 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.
RESET AND POWER-DOWN
The reset pin 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 a lock condition,
an initialization routine runs inside the AD1974. This initializa-
tion lasts for approximately 256 master clock cycles.
The PLL and Clock Control 0 register and the ADC Control 1
register power down their respective sections using power down
bits. All other register settings are retained. The PD/RST pin
should be pulled low by an external resistor to guarantee proper
startup.
AD1974 Data Sheet
Rev. D | Page 12 of 24
Table 11. Standalone Mode Selection
ADC Clocks CIN COUT CCLK CLATCH
Slave 0 0 0 0
Master 0 1 0 0
D0
D0
D8
D8
D22D23 D9
D9
C
LATCH
CCLK
CIN
COUT
t
CCH
t
CCL
t
CDS
t
CDH
t
CLS
t
CCP
t
CLH
t
COTS
t
COD
t
COE
06614-010
Figure 5. Format of the SPI Signal
SERIAL CONTROL PORT
The AD1974 has an SPI control port that permits programming
and reading back of the internal control registers for the ADCs,
DACs, and clock system. A standalone mode is also available
for operation without serial control; standalone is configured at
reset by connecting CIN, CCLK, and CLATCH to ground. In
standalone mode, all registers are set to default, except the internal
MCLK enable, which is set to 1. The ADC, ABCLK, and ALRCLK
clock ports are set to master/slave by the connecting the COUT
pin to either DVDD or ground. Standalone mode only supports
stereo mode with an I2S data format and 256 fS MCLK rate. Refer
to Table 11 for details. If CIN, CCLK, and CLATCH are not
grounded, the AD1974 SPI port is active. 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
AD1939 recognizes the presence of a microcontroller.
The SPI control port of the AD1974 is a 4-wire serial control
port. The format is similar to that of the Motorola SPI® format
except that 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. Figure 5 shows the format of the SPI signal.
The first byte is a global address with a read/write bit. For the
AD1974, the address is 0x04, shifted left one bit due to the R/W
bit. The second byte is the AD1974 register address and the
third byte is the data.
POWER SUPPLY AND VOLTAGE REFERENCE
The AD1974 is designed for 3.3 V supplies. Separate power
supply pins (Pin 5, Pin 13, Pin 33, Pin 37, and Pin 38) are pro-
vided 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 μF should also be placed
on the same PC board as the ADC. For critical applications,
improved performance is obtained with separate supplies for
the analog and digital sections. If this is not possible, it is rec-
ommended 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 internal voltage reference (VREF) is brought out
on FILTR and should be bypassed as close as possible to the
AD1974 with a parallel combination of 10 μF and 100 nF. Any
external current drawn should be limited to less than 50 μA.
VREF can be disabled in the PLL and Clock Control 1 register
and FILTR can be driven from an external source. The ADC
input gain varies by the inverse ratio.
CM is the internal common-mode reference. It should be
bypassed as close as possible to the AD1974, with a parallel
combination of 47 μF 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.
SERIAL DATA PORTS—DATA FORMAT
The four ADC channels use a common serial bit clock (ABCLK)
and a 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 11.
The ADC 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 ADC serial formats and serial clock polarity
are programmable according to the ADC Control 1 register.
The ADC serial ports are programmable to become the bus
masters according to the ADC Control 2 register. By default,
both ADC serial ports are in the slave mode.
Data Sheet AD1974
Rev. D | Page 13 of 24
TDM MODES
The AD1974 serial ports also have several different TDM serial
data modes. The first and most commonly used configuration
is shown in Figure 6 where the ADC serial port outputs one
data stream consisting of four on-chip ADCs followed by four
unused slots. In this mode, ABCLK is set to 256 fS (8-channel
TDM mode).
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 AD1974 allows system configurations with more than four
ADC channels (see Figure 7 and Figure 8) that use 8 ADCs and
16 ADCs. In this mode, four AUX channel slots in the TDM out-
put stream follow four on-chip ADC channel slots. It should be
noted that due to the high ABCLK frequency, this mode is
available only in the 48 kHz/44.1 kHz/32 kHz sample rate.
SLOT 1
LEFT 1
SLOT 2
RIGHT 1
SLOT 3
LEFT 2
SLOT 4
RIGHT 2
MSB MSB–1 MSB–2 ADATA
ABCLK
ALRCLK
UNUSED UNUSED UNUSED UNUSED
A
LRCLK
ABCLK
ADATA
256 BCLKs
32 BCLKs
06614-016
Figure 6. ADC TDM (8-Channel I2S Mode)
Table 12. Pin Function Changes in TDM and AUX Modes
Pin Name Stereo Mode TDM Mode AUX Mode
ASDATA1 ADC1 data output ADC TDM data output ADCTDM data output
ASDATA2 ADC2 data output ADC TDM data input Not used (float)
AUXDATA1 Not used (ground) Not used (ground) AUXDATA in 1 (from external ADC1)
AUXDATA2 Not used (ground) Not used (ground) AUXDATA in 2 (from external ADC2)
ALRCLK ADC LRCLK input/output ADC TDM frame sync input/output ADCTDM frame sync input/output
ABCLK ADC BCLK input/output ADC TDM BCLK input/output ADCTDM BCLK input/output
AUXLRCLK Not used (ground) Not used (ground) AUXLRCLK input/output
AUXBCLK Not used (ground) Not used (ground) AUXBCLK input/output
ABCLK
ALRCLK
AUXLRCLK
(AUX PORT)
ASDATA1
(TDM_OUT)
AUXBCLK
(AUX PORT)
AUXDATA1
(AUX1_IN)
AUXDATA2
(AUX2_IN)
ADCL1 ADCR1 ADCL2 ADCR2 AUXL1 AUXR1 AUXL2 AUXR2
FOUR-ON-CHIP DAC CHANNELS
32 BITS
LEFT RIGHT
MSB
MSB MSB
MSB MSB
FOUR-AUX ADC CHANNELS
06614-050
Figure 7. 8-Channel AUX ADC Mode
AD1974 Data Sheet
Rev. D | Page 14 of 24
LEFT RIGHT
MSB MSB
MSB MSB
MSB
ADCL1 ADCR1 ADCL2 ADCR2 AUXL1 AUXR1 AUXL2 AUXR2 UNUSED UNUSED UNUSED UNUSEDUNUSED UNUSED UNUSED UNUSED
FOUR-ON-CHIP
ADC CHANNELS AUXILIARY ADC CHANNELS UNUSED SLOTS
32 BITS
06614-052
AUXLRCLK
(AUX PORT)
AUXBCLK
(AUX PORT)
AUXDATA1
(AUX1_IN)
AUXDATA2
(AUX2_IN)
ALRCLK
ABCLK
ASDATA1
(TDM_OUT)
Figure 8. 16-Channel AUX ADC Mode
DAISY-CHAIN MODE
The AD1974 also allows a daisy-chain configuration to
expand the system to 8 ADCs and 16 ADCs (see Figure 9 and
Figure 10). 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 9. The second configuration is with an
ABCLK at 512 fS shown in Figure 10. 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
AD1974 must be grounded in all modes of operation. The
second AD1974 is the device attached to the DSP TDM port.
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 14 for a typical AD1974
configuration with two external stereo ADCs.
Figure 11 through Figure 13 show the serial mode formats.
For maximum flexibility, the polarity of LRCLK and BCLK
are programmable. All of the clocks are shown with their
normal polarity. The default mode is I2S.
ALRCLK
ABCLK
ASDATA2 (TDM_IN
OF THE SECOND AD1974
IN THE CHAIN) ADCL1 ADCR1 ADCL2 ADCR2
FOUR ADC CHANNELS OF THE FIRST IC IN THE CHAINFOUR ADC CHANNELS OF THE SECOND IC IN THE CHAIN
ASDATA1 (TDM_OUT
OF THE SECOND AD1974
IN THE CHAIN)
ADCL1 ADCR1 ADCL2 ADCR2 ADCL1 ADCR1 ADCL2 ADCR2
32 BITS
MSB
DSP
SECOND
AD1974
FIRST
AD1974
06614-056
Figure 9. ADC TDM Daisy-Chain Mode (256 fS ABCLK, Two AD1974 Daisy Chains)
Data Sheet AD1974
Rev. D | Page 15 of 24
ALRCLK
ABCLK
FOUR ADC CHANNELS OF
THE SECOND IC IN THE CHAIN
FOUR ADC CHANNELS OF
THE FIRST IC IN THE CHAIN
ADCL1 ADCR1 ADCL2 ADCR2 ADCL1 ADCR1 ADCL2 ADCR2 UNUSED
UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED UNUSED
ASDATA1 (TDM_OUT
OF THE SECOND AD1974
IN THE CHAIN)
ADCL1 ADCR1 ADCL2 ADCR2
ASDATA2 (TDM_IN
OF THE SECOND AD1974
IN THE CHAIN)
32 BITS
MSB
DSP
SECOND
AD1974
FIRST
AD1974
06614-057
Figure 10. ADC TDM Daisy-Chain Mode (512 fS ABCLK, Two AD1974 Daisy Chains)
ALRCLK
ABCLK
ASDATA
ALRCLK
ABCLK
ASDATA
ALRCLK
ABCLK
ASDATA LSB LSB
LSB
LSB
LSB LSB
LEFT CHANNEL RIGHT CHANNEL
RIGHT CHANNEL
LEFT CHANNEL
LEFT CHANNEL RIGHT CHANNEL
MSB MSB
MSB
MSB
MSB MSB
RIGHT JUSTIFIED MODE—SELECT NUMBER OF BITS PER CHANNEL
DSP MODE—16 BITS TO 24 BITS PER CHANNEL
I2S MODE—16 BITS TO 24 BITS PER CHANNEL
LEFT JUSTIFIED MODE—16 BITS TO 24 BITS PER CHANNEL
ALRCLK
ABCLK
ASDATA LSB LSB
NOTES
1. DSP MODE DOES NOT IDENTIFY CHANNEL.
2. LRCLK NORMALLY OPERATES AT fS EXCEPT FOR DSP MODE WHICH IS 2 × fS.
3. BCLK FREQUENCY IS NORMALLY 64 × LRCLK BUT MAY BE OPERATED IN BURST MODE.
MSB MSB
1/fS
06614-013
Figure 11. Stereo Serial Modes
AD1974 Data Sheet
Rev. D | Page 16 of 24
06614-014
AUXBCLK
AUXRCLK
AUXDATA
LEFT JUSTIFIED
MODE
AUXDATA
RIGHT JUSTIFIED
MODE
AUXDATA
I
2
S JUSTIFIED
MODE
t
XDH
t
XDH
t
XDH
t
XDS
t
XDS
t
XDH
t
XDS
t
XLH
t
XDS
t
XLS
t
XBL
t
XBH
MSB LSB
MSB
MSB–1MSB
Figure 12. Auxiliary Serial Timing
ABCLK
ALRCLK
ASDATA
LEFT JUSTIFIED
MODE
ASDATA
RIGHT JUSTIFIED
MODE
ASDATA
I
2
S JUSTIFIED
MODE
tABH
LSB
MSB
MSB
MSB
MSB–1
tABL
tALS
tABDD
tABDD
tABDD
tALH
0
6614-015
Figure 13. ADC Serial Timing
Table 13. Pin Function Changes in TDM and AUX Modes (Replication of Table 12)
Pin Name Stereo Mode TDM Mode AUX Mode
ASDATA1 ADC1 data output ADC TDM data output ADCTDM data output
ASDATA2 ADC2 data output ADC TDM data input Not used (float)
AUXDATA1 Not used (ground) Not used (ground) AUXDATA in 1 (from external ADC1)
AUXDATA2 Not used (ground) Not used (ground) AUXDATA in 2 (from external ADC2)
ALRCLK ADC LRCLK input/output ADC TDM Frame Sync input/output ADCTDM frame sync input/output
ABCLK ADC BCLK input/output ADC TDM BCLK input/output ADCTDM BCLK input/output
AUXLRCLK Not used (ground) Not used (ground) AUXLRCLK input/output
AUXBCLK Not used (ground) Not used (ground) AUXBCLK input/output
Data Sheet AD1974
Rev. D | Page 17 of 24
AUX
ADC 1
LRCLK
BCLK
DATA
MCLK
AUX
ADC 2
LRCLK
BCLK
DATA
MCLK
30MHz
12.288MHz
SHARC IS RUNNING
IN SLAVE MODE
(INTERRUPT-DRIVEN)
SHARC
AD1974
TDM MASTER
AUX MASTER
FSYNC-TDM (RFS)
RxCLK
RxDATA
TxCLK
TFS (NC)
AUXBCLK
AUXLRCLK
AUXDATA1
AUXDATA2
MCLK
ASDATA1 ALRCLK ABCLK
06614-019
Figure 14. Example of AUX Mode Connection to SHARC® (AD1974 as TDM Master/AUX Master Shown)
AD1974 Data Sheet
Rev. D | Page 18 of 24
CONTROL REGISTERS
The global address for the AD1974 is 0x04, shifted left one bit due to the R/W bit. All registers are reset to 0.
Note that the first setting in each control register parameter is the default setting.
Table 14. Register Format
Global Address R/W Register Address Data
Bit 23:17 16 15:8 7:0
Table 15. Register Addresses Description
Address Function
0 PLL and Clock Control 0
1 PLL and Clock Control 1
2 AUXPORT Control 0
3 AUXPORT Control 1
4 AUXPORT Control 2
5 Reserved
6 Reserved
7 Reserved
8 Reserved
9 Reserved
10 Reserved
11 Reserved
12 Reserved
13 Reserved
14 ADC Control 0
15
ADC Control 1
16 ADC Control 2
PLL AND CLOCK CONTROL REGISTERS
Table 16. PLL and Clock Control 0
Bit Value Function Description
0 0 Normal operation PLL power-down
1 Power-down
2:1 00 INPUT 256 (×44.1 kHz or 48 kHz) MCLKI/XI pin functionality (PLL active), master clock rate setting
01
INPUT 384 (×44.1 kHz or 48 kHz)
10 INPUT 512 (×44.1 kHz or 48 kHz)
11 INPUT 768 (×44.1 kHz or 48 kHz)
4:3 00 XTAL oscillator enabled MCLKO/XO pin, master clock rate setting
01 256 × fS VCO output
10 512 × fS VCO output
11 Off
6:5 00 MCLKI/XI PLL input
01 AUXLRCLK
10 ALRCLK
11 Reserved
7 0 Disable: ADC idle Internal MCLK enable
1 Enable: ADC active
Data Sheet AD1974
Rev. D | Page 19 of 24
Table 17. PLL and Clock Control 1
Bit Value Function Description
0 0 PLL clock AUXPORT clock source select
1 MCLK
1 0 PLL clock ADC clock source select
1 MCLK
2 0 Enabled On-chip voltage reference
1 Disabled
3 0 Not locked PLL lock indicator (read only)
1 Locked
7:4 0000 Reserved
AUXPORT CONTROL REGISTERS
Table 18. AUXPORT Control 0
Bit Value Function Description
0 0 Reserved Reserved
1 Reserved
2:1 00 32 kHz/44.1 kHz/48 kHz Sample rate
01 64 kHz/88.2 kHz/96 kHz
10 128 kHz/176.4 kHz/192 kHz
11 Reserved
5:3 000 1 AUXDATA delay (AUXBCLK periods)
001 0
010 8
011
12
100 16
101 Reserved
110 Reserved
111 Reserved
7:6 00 Stereo (normal) Serial format
01 Reserved
10 ADC AUX mode (ADC-, TDM-coupled)
11 Reserved
Table 19. AUXPORT Control 1
Bit Value Function Description
0 0 Reserved
1 Reserved
2:1 00 64 (two channels) AUXBCLKs per frame
01 Reserved
10 Reserved
11 Reserved
3 0 Left low AUXLRCLK polarity
1 Left high
4 0 Slave AUXLRCLK master/slave
1 Master
5 0 Slave AUXBCLK master/slave
1 Master
6 0 AUXBCLK pin AUXBCLK source
1 Internally generated
7 0 Normal AUXBCLK polarity
1 Inverted
AD1974 Data Sheet
Rev. D | Page 20 of 24
Table 20. AUXPORT Control 2
Bit Value Function Description
0
0
Reserved
1 Reserved
2:1 00 Reserved
01 Reserved
10 Reserved
11 Reserved
4:3 00 24 Word width
01 20
10 Reserved
11 16
5 0 Reserved
1 Reserved
7:6 00 Reserved
ADC CONTROL REGISTERS
Table 21. ADC Control 0
Bit Value Function Description
0 0 Normal Power-down
1 Power down
1 0 Off High-pass filter
1 On
2 0 Unmute ADC1L mute
1 Mute
3 0 Unmute ADC1R mute
1 Mute
4 0 Unmute ADC2L mute
1 Mute
5 0 Unmute ADC2R mute
1 Mute
7:6 00 32 kHz/44.1 kHz/48 kHz Output sample rate
01
64 kHz/88.2 kHz/96 kHz
10 128 kHz/176.4 kHz/192 kHz
11 Reserved
Table 22. ADC Control 1
Bit Value Function Description
1:0 00 24 Word width
01 20
10 Reserved
11 16
4:2 000 1 SDATA delay (BCLK periods)
001 0
010 8
011 12
100 16
101 Reserved
110 Reserved
111 Reserved
Data Sheet AD1974
Rev. D | Page 21 of 24
Bit Value Function Description
6:5 00 Stereo Serial format
01 TDM (daisy chain)
10 ADC AUX mode (TDM-coupled)
11 Reserved
7 0 Latch in midcycle (normal) BCLK active edge (TDM_IN)
1 Latch in at end of cycle (pipeline)
Table 23. ADC Control 2
Bit Value Function Description
0 0 50/50 (allows 32-/24-/20-/16-BCLK per channel) LRCLK format
1 Pulse (32-BCLK/channel)
1 0 Drive out on falling edge (DEF) BCLK polarity
1 Drive out on rising edge
2 0 Left low LRCLK polarity
1 Left high
3 0 Slave LRCLK master/slave
1 Master
5:4 00 64 BCLKs per frame
01 128
10 256
11 512
6 0 Slave BCLK master/slave
1 Master
7 0 ABCLK pin BCLK source
1 Internally generated
ADDITIONAL MODES
The AD1974 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 15 for an example of an ADC TDM data transmission
mode that does not require high speed ABCLK. This configura-
tion is applicable when the AD1974 master clock is generated
by the PLL with the ALRCLK as the PLL reference frequency.
To relax the requirement for the setup time of the AD1974 in
cases of high speed TDM data transmission, the AD1974 can
latch in the data using the falling edge of ABCLK. This effec-
tively 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 16 shows this pipeline mode of
data transmission.
ALRCLK
INTERNAL
ABCLK
ASDATA2
ALRCLK
INTERNAL
ABCLK
ASDATA2
32 BITS
06614-059
Figure 15. Serial ADC Data Transmission in TDM Format Without ABCLK
(Applicable Only If PLL Locks to ALRCLK)
AD1974 Data Sheet
Rev. D | Page 22 of 24
ALRCLK
ABCLK
A
SDATA1
DATA MUST BE VALID
AT THIS BCLK EDGE
MSB
0
6614-060
Figure 16. I2S Pipeline Mode in ADC Serial Data Transmission
(Applicable in Stereo and TDM Useful for High Frequency TDM Transmission)
Data Sheet AD1974
Rev. D | Page 23 of 24
APPLICATION CIRCUITS
Typical applications circuits are shown in Figure 17 and Figure 18. Figure 17 shows a typical ADC input filter circuit. Recommended loop
filters for LR clock and master clock as the PLL reference are shown in Figure 18.
2
1
3OP275
–
+
6
7
5OP275
–
+
5.76kΩ
5.76kΩ237Ω
5.76kΩ
120p
F
600Z
A
UDIO
INPUT
100pF
5.76kΩ
120pF
4.7µF
+
237Ω
4.7µF
+
100pF
1nF
NP0
1nF
NP0
ADCxN
ADCxP
06614-023
Figure 17. Typical ADC Input Filter Circuit
39nF
+2.2nF
LF LRCL
K
A
VDD2
3.32kΩ
5.6nF
390pF
LF MCLK
AVDD2
562Ω
06614-027
Figure 18. Recommended Loop Filters for LRCLK or MCLK PLL Reference
AD1974 Data Sheet
Rev. D | Page 24 of 24
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC STANDARDS MS-026-BBC
TOP VIEW
(PINS DOWN)
1
12
13
25
24
36
37
48
0.27
0.22
0.17
0.50
BSC
LEAD PITCH
1.60
MAX
0.75
0.60
0.45
VIEW A
PIN 1
0.20
0.09
1.45
1.40
1.35
0.08
COPLANARITY
VIEW A
ROTATED 90° CCW
SEATING
PLANE
7°
3.5°
0°
0.15
0.05
9.20
9.00 SQ
8.80
7.20
7.00 SQ
6.80
051706-A
Figure 19. 48-Lead Low Profile Quad Flat Package [LQFP]
(ST-48)
Dimensions shown in millimeters
ORDERING GUIDE
Model1, 2, 3 Temperature Range Package Description Package Option
AD1974YSTZ −40°C to +105°C 48-Lead LQFP ST-48
AD1974YSTZ-RL −40°C to +105°C 48-Lead LQFP, 13” Tape and Reel ST-48
AD1974WBSTZ −40°C to +105°C 48-Lead LQFP ST-48
AD1974WBSTZ-RL −40°C to +105°C 48-Lead LQFP, 13” Tape and Reel ST-48
EVAL-AD1974AZ Evaluation Board
1 Z = RoHS Compliant Part.
2 W = Qualified for Automotive Applications.
3 SPI control port.
AUTOMOTIVE PRODUCTS
The AD1974W models are available with controlled manufacturing to support the quality and reliability requirements of automotive
applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers
should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in
automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to
obtain the specific Automotive Reliability reports for these models.
©2007–2013 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D06614-0-3/13(D)