EVAL-AD1870EB [ADI]
Single-Supply 16-Bit Stereo ADC; 单电源， 16位立体声ADC
| 型号： | EVAL-AD1870EB |
| 厂家： | 
ADI |
| 描述： | Single-Supply 16-Bit Stereo ADC |
| 文件： | 总20页 (文件大小：268K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Single-Supply
a
16-Bit ⌺-⌬ Stereo ADC
AD1870*
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Single 5 V Power Supply
Single-Ended Dual-Channel Analog Inputs
92 dB (Typ) Dynamic Range
90 dB (Typ) S/(THD + N)
0.006 dB Decimator Pass-Band Ripple
Fourth Order, 64
؋
Oversampling ⌺-⌬ Modulator Three-Stage, Linear-Phase Decimator
256
؋
fS or 384 ؋
fS Input Clock Less than 100 W (Typ) Power-Down Mode
Input Overrange Indication
CLOCK
DIVIDER
LRCK
WCLK
BCLK
1
2
28 CLKIN
SERIAL OUTPUT
INTERFACE
27 TAG
26
25 DV
3
SOUT
THREE-STAGE FIR
DECIMATION
FILTER
THREE-STAGE FIR
DECIMATION
FILTER
4
2
DV
1
DD
DGND2
DD
5
DGND1
RDEDGE
S/M
24
6
23 RESET
22 MSBDLY
21 RLJUST
On-Chip Voltage Reference
Flexible Serial Output Interface
28-Lead SOIC Package
DAC
DAC
DAC
DAC
7
8
384/256
APPLICATIONS
9
20
AV
DD
AGND
Consumer Digital Audio Receivers
Digital Audio Recorders, Including Portables
CD-R, DCC, MD, and DAT
Multimedia and Consumer Electronics Equipment
Sampling Music Synthesizers
10
11
12
V
R
V
L
19
18
17
16
15
IN
IN
CAPR1
CAPR2
AGNDR
CAPL1
CAPL2
AGNDL
SINGLE-TO-
DIFFERENTIAL INPUT DIFFERENTIAL INPUT
CONVERTER CONVERTER
SINGLE-TO-
13
14
VOLTAGE
REFERENCE
V
R
V
L
REF
REF
AD1870
PRODUCT OVERVIEW
The AD1870 is a stereo, 16-bit oversampling ADC based on
sigma-delta (⌺-⌬) technology intended primarily for digital
audio bandwidth applications requiring a single 5 V power supply.
Each single-ended channel consists of a fourth order one-bit
noise shaping modulator and a digital decimation filter. An on-chip
voltage reference, stable over temperature and time, defines the
full-scale range for both channels. Digital output data from both
channels are time multiplexed to a single, flexible serial inter-
face. The AD1870 accepts a 256 × fS or a 384 × fS input clock
(fS is the sampling frequency) and operates in both serial port
Master and Slave Modes. In Slave Mode, all clocks must be ex-
ternally derived from a common source.
shapes the one-bit comparator’s quantization noise out of the
audio pass band. The high order of the modulator randomizes the
modulator output, reducing idle tones in the AD1870 to very
low levels. Because its modulator is single bit, the AD1870 is
inherently monotonic and has no mechanism for producing
differential linearity errors.
The input section of the AD1870 uses autocalibration to correct
any dc offset voltage present in the circuit, provided that the inputs
are ac-coupled. The single-ended dc input voltage can swing
between 0.7 V and 3.8 V typically. The AD1870 antialias input
circuit requires four external 470 pF NPO ceramic chip filter
capacitors, two for each channel. No active electronics are needed.
Decoupling capacitors for the supply and reference pins are
also required.
Input signals are sampled at 64 × fS onto internally buffered
switched capacitors, eliminating external sample-and-hold ampli-
fiers and minimizing the requirements for antialias filtering at the
input. With simplified antialiasing, linear phase can be preserved
across the pass band. The on-chip single-ended-to-differential sig-
nal converters save the board designer from having to provide
them externally. The AD1870’s internal differential architecture
provides increased dynamic range and excellent power supply
rejection characteristics. The AD1870’s proprietary fourth order
differential switched-capacitor ⌺-⌬ modulator architecture
The dual-digital decimation filters are triple-stage, finite impulse
response filters for effectively removing the modulator’s high
frequency quantization noise and reducing the 64 × fS single-bit
output data rate to an fS word rate. They provide linear phase
and a narrow transition band that properly digitizes 20 kHz signals
at a 44.1 kHz sampling frequency. Pass-band ripple is less than
0.006 dB, and stop-band attenuation exceeds 90 dB.
*Protected by U.S. Patent Numbers 5055843, 5126653; others pending.
(Continued on Page 7)
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
www.analog.com
© Analog Devices, Inc., 2002
AD1870–SPECIFICATIONS
TEST CONDITIONS UNLESS OTHERWISE NOTED
Supply Voltages
5.0
25
12.288
991.768
–0.5
V
°C
MHz
Ambient Temperature
Input Clock (fCLKIN) [256 × fS]
Input Signal
Hz
dB Full Scale
Measurement Bandwidth
23.2 Hz to 19.998 kHz
Load Capacitance on Digital Outputs 50
pF
V
V
Input Voltage HI (VIH)
Input Voltage LO (VIL)
2.4
0.8
Master Mode, Data I2S-Justified (Refer to Figure 14).
Device Under Test (DUT) bypassed and decoupled as shown in Figure 3.
DUT is antialiased and ac-coupled as shown in Figure 2. DUT is calibrated.
Values in bold typeface are tested; all others are guaranteed but not tested.
ANALOG PERFORMANCE
Min
Typ
Max
Unit
Resolution
16
Bits
Dynamic Range (20 Hz to 20 kHz, –60 dB Input)
Without A-Weight Filter
With A-Weight Filter
Signal to (THD + Noise)
Signal to THD
89
92
86.5
93
96
90.5
94
dB
dB
dB
dB
Analog Inputs
Single-Ended Input Range ( Full Scale)*
Input Impedance at Each Input Pin
VREF
VREF 1.49
32
2.25
V
kΩ
V
2.05
2.55
DC Accuracy
Gain Error
Interchannel Gain Mismatch
Gain Drift
Midscale Offset Error (After Calibration)
Midscale Drift
0.5
0.05
115
3
–0.2
–110
؎2.5
%
dB
ppm/°C
LSBs
LSB/°C
dB
؎20
Crosstalk (EIAJ Method)
–100
*VIN p-p = VREF × 1.326.
V × 1.326
REF
Minimum Input = VREF
Maximum Input = VREF
–
2
V × 1.326
REF
+
2
–2–
REV. A
AD1870
DIGITAL I/O
Min
2.4
Typ
Max
Unit
Input Voltage HI (VIH)
Input Voltage LO (VIL)
Input Leakage (IIH @ VIH = 5 V)
Input Leakage (IIL @ VIL = 0 V)
Output Voltage HI (VOH @ IOH = –2 mA)
Output Voltage LO (VOL @ IOL = 2 mA)
Input Capacitance
V
V
µA
µA
V
V
pF
0.8
10
10
2.4
0.4
15
DIGITAL TIMING (Guaranteed over –40°C to +85°C, DVDD = AVDD = 5 V 5%. Refer to Figures 17–19.)
Min
Typ
Max
Unit
tCLKIN
fCLKIN
tCPWL
tCPWH
tRPWL
tBPWL
tBPWH
CLKIN Period
48
1.28
15
15
50
15
15
81
12.288
780
20.48
ns
MHz
ns
ns
ns
ns
ns
CLKIN Frequency (1/tCLKIN
CLKIN LO Pulsewidth
CLKIN HI Pulsewidth
RESET LO Pulsewidth
BCLK LO Pulsewidth
BCLK HI Pulsewidth
)
tDLYCKB
tDLYBLR
tDLYBWR
tDLYBWF
tDLYDT
tSETLRBS
tDLYLRDT
CLKIN Rise to BCLK Xmit (Master Mode)
BCLK Xmit to LRCK Transition (Master Mode)
BCLK Xmit to WCLK Rise
15
15
10
10
10
ns
ns
ns
ns
ns
ns
BCLK Xmit to WCLK Fall
BCLK Xmit to DATA/TAG Valid (Master Mode)
LRCK Setup to BCLK Sample (Slave Mode)
LRCK Transition to DATA/TAG Valid (Slave Mode)
No MSB Delay Mode (for MSB Only)
WCLK Setup to BCLK Sample (Slave Mode)
Data Position Controlled by WCLK Input Mode
BCLK Xmit to DATA/TAG Valid (Slave Mode)
All Bits Except MSB in No MSB Delay Mode
All Bits in MSB Delay Mode
10
10
40
ns
ns
tSETWBS
tDLYBDT
40
ns
POWER
Min
Typ
Max
Unit
Supplies
Voltage, Analog and Digital
4.75
5
5.25
V
Analog Current
Analog Current–Power-Down (CLKIN Running)
Digital Current
Digital Current–Power-Down (CLKIN Running)
Dissipation
43
25
9.3
50
52
mA
µA
mA
µA
12
Operation–Both Supplies
Operation–Analog Supply
Operation–Digital Supply
Power-Down–Both Supplies (CLKIN Running)
Power-Down–Both Supplies (CLKIN Not Running)
Power Supply Rejection (See TPC 5)
1 kHz 300 mV p-p Signal at Analog Supply Pins
20 kHz 300 mV p-p Signal at Analog Supply Pins
Stop Band (>0.55 × fS)—any 300 mV p-p Signal
263
216
47
375
375
315
260
55
mW
mW
mW
µW
µW
90
68
110
dB
dB
dB
REV. A
–3–
AD1870
TEMPERATURE RANGE
Min
Typ
Max
Unit
Specifications Guaranteed
Functionality Guaranteed
Storage
+25
°C
°C
°C
–40
–60
+85
+100
DIGITAL FILTER CHARACTERISTICS
Min
Typ
Max
Unit
Decimation Factor
64
Pass-Band Ripple
Stop-Band* Attenuation
48 kHz fS (at Recommended Crystal Frequencies)
Pass Band
0.006
21.6
20
dB
dB
90
0
26.4
kHz
kHz
Stop Band
44.1 kHz fS (at Recommended Crystal Frequencies)
Pass Band
Stop Band
0
kHz
kHz
24.25
32 kHz fS (at Recommended Crystal Frequencies)
Pass Band
Stop Band
0
17.6
14.4
kHz
kHz
Other fS
Pass Band
Stop Band
Group Delay
Group Delay Variation
0
0.55
0.45
fS
fS
s
36/fS
0
µs
*Stop band repeats itself at multiples of 64 × fS, where fS is the output word rate. Thus the digital filter will attenuate to 0 dB across the frequency spectrum except
for a range 0.55 × fS wide at multiples of 64 × fS.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS
Min
Typ
Max
Unit
DVDD1 to DGND1 and DVDD2 to DGND2
AVDD to AGND/AGNDL/AGNDR
Digital Inputs
Analog Inputs
AGND to DGND
0
0
+6
+6
V
V
V
V
V
DGND – 0.3
AGND – 0.3
–0.3
DVDD + 0.3
AVDD + 0.3
+0.3
Reference Voltage
Soldering (10 sec)
Indefinite Short Circuit to Ground
+300
°C
ORDERING GUIDE
Package
Description
Package
Option
Model
Temperature
–40°C to +85°C
–40°C to +85°C
AD1870AR
SOIC
R-28
AD1870AR–REEL
EVAL-AD1870EB
SOIC
R-28 in 13” Reel (1000 pcs.)
Evaluation Board
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
the AD1870 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.
WARNING!
ESD SENSITIVE DEVICE
–4–
REV. A
AD1870
PIN FUNCTION DESCRIPTIONS
Pin
Signal to Total Harmonic Distortion (S/THD)
The ratio of the rms value of the fundamental input signal to the
rms sum of all harmonically related spectral components in the
pass band, expressed in decibels.
Input/
Pin
Output Name
Description
1
2
3
4
5
6
7
8
I/O
I/O
I/O
I
I
I
I
I
I
I
O
O
I
O
O
I
O
O
I
I
I
I
I
LRCK
WCLK
BCLK
DVDD1
DGND1
Left/Right Clock
Word Clock
Bit Clock
5 V Digital Supply
Digital Ground
Pass Band
The region of the frequency spectrum unaffected by the attenu-
ation of the digital decimator’s filter.
Pass-Band Ripple
The peak-to-peak variation in amplitude response from equal-
amplitude input signal frequencies within the pass band,
expressed in decibels.
RDEDGE Read Edge Polarity Select
S/M
384/256
AVDD
Slave/Master Select
Clock Mode
5 V Analog Supply
Left Channel Input
Left External Filter Capacitor 1
Left External Filter Capacitor 2
Left Analog Ground
Left Reference Voltage Output
Right Reference Voltage Output
Right Analog Ground
Right External Filter Capacitor 2
Right External Filter Capacitor 1
Right Channel Input
Stop Band
The region of the frequency spectrum attenuated by the digi-
tal decimator’s filter to the degree specified by stop-band
attenuation.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
V
INL
CAPL1
CAPL2
AGNDL
Gain Error
With a near full-scale input, the ratio of actual output to
expected output, expressed as a percentage.
V
V
REFL
REFR
Interchannel Gain Mismatch
With identical near full-scale inputs, the ratio of outputs of the
two stereo channels, expressed in decibels.
AGNDR
CAPR2
CAPR1
Gain Drift
Change in response to a near full-scale input with a change in
temperature, expressed as parts-per-million (ppm) per °C.
V
INR
Midscale Offset Error
Output response to a midscale dc input, expressed in least
significant bits (LSBs).
AGND
RLJUST
Analog Ground
Right/Left Justify
MSBDLY Delay MSB One BCLK Period
Midscale Drift
RESET
DGND2
DVDD2
SOUT
TAG
Reset
Change in midscale offset error with a change in temperature,
expressed as parts-per-million (ppm) per °C.
I
I
O
O
I
Digital Ground
5 V Digital Supply
Serial Data Output
Serial Overrange Output
Master Clock
Crosstalk (EIAJ Method)
Ratio of response on one channel with a grounded input to a
full-scale 1 kHz sine wave input on the other channel, expressed
in decibels.
CLKIN
Power Supply Rejection
DEFINITIONS
Dynamic Range
With no analog input, signal present at the output when a
300 mV p-p signal is applied to the power supply pins, ex-
pressed in decibels of full scale.
The ratio of a full-scale output signal to the integrated output noise
in the pass band (20 Hz to 20 kHz), expressed in decibels (dB).
Dynamic range is measured with a –60 dB input signal and is equal
to (S/(THD + N)) 60 dB. Note that spurious harmonics are below
the noise with a –60 dB input, so the noise level establishes the
dynamic range. The dynamic range is specified with and with-
out an A-Weight filter applied.
Group Delay
Intuitively, the time interval required for an input pulse to
appear at the converter’s output, expressed in milliseconds
(ms). More precisely, the derivative of radian phase with respect
to radian frequency at a given frequency.
Group Delay Variation
Signal to Total Harmonic Distortion + Noise
(S/(THD + N))
The ratio of the root-mean-square (rms) value of the fundamen-
tal input signal to the rms sum of all other spectral components
in the pass band, expressed in decibels.
The difference in group delays at different input frequencies.
Specified as the difference between the largest and smallest
group delays in the pass band, expressed in microseconds (µs).
–5–
REV. A
AD1870–Typical Performance Characteristics
–80
–82
–84
–86
–88
–90
–92
–94
–96
–98
–100
0
–20
–40
–60
–80
–100
–120
–140
–60
–50
–40
–30
–20
–10
–0.5
0
2
4
6
8
10 12 14 16 18 20 22
FREQUENCY – kHz
24
INPUT AMPLITUDE – dBFS
TPC 4. THD + N vs. Input Amplitude at 1 kHz
TPC 1. 1 kHz Tone at –0.5 dBFS (16 k-Point FFT)
–60
–65
–70
–75
–80
–85
–90
–95
–100
0
–20
–40
–60
–80
–100
–120
–140
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10 12 14 16 18 20 22
24
FREQUENCY – kHz
FREQUENCY – kHz
TPC 5. Power Supply Rejection to 300 mV p-p on AVDD
TPC 2. 1 kHz Tone at –10 dBFS (16 k-Point FFT)
–80
–85
–80
–82
–84
–86
–88
–90
–92
–94
–96
–98
–100
–90
–95
–100
–105
–110
–115
–120
0
2
4
6
8
10
12
14
16
18
20
0
2
4
6
8
10
12
14
16
18
20
FREQUENCY – kHz
FREQUENCY – kHz
TPC 6. Channel Separation vs. Frequency at –0.5 dBFS
TPC 3. THD + N vs. Frequency at –0.5 dBFS
–6–
REV. A
AD1870
10
0
⌺-⌬ architectures “shape” the quantization noise-transfer function
in a nonuniform manner. Through careful design, this transfer
function can be specified to high-pass filter the quantization
noise out of the audio band into higher frequency regions. The
AD1870 also incorporates a feedback resonator from the fourth
integrator’s output to the third integrator’s input. This resona-
tor does not affect the signal transfer function but allows the
flexible placement of a zero in the noise transfer function for
more effective noise shaping.
–10
–20
–30
–40
–50
–60
–70
–80
Oversampling by 64 simplifies the implementation of a high
performance audio analog-to-digital conversion system. Antialias
requirements are minimal; a single pole of filtering will usually
suffice to eliminate inputs near fS and its higher multiples.
–90
–100
–110
–120
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
A fourth order architecture was chosen both to strongly shape
the noise out of the audio band and to help break up the idle
tones produced in all ⌺-⌬ architectures. These architectures
have a tendency to generate periodic patterns with a constant dc
input, a response that looks like a tone in the frequency domain.
These idle tones have a direct frequency dependence on the input
dc offset and an indirect dependence on temperature and time
as it affects the dc offset. The AD1870 suppresses idle tones 20
dB or better below the integrated noise floor.
NORMALIZED fS
TPC 7. Digital Filter Signal Transfer Function to fS
(
Continued from Page 1 )
The flexible serial output port produces data in two’s complement,
MSB-first format. The input and output signals are TTL
compatible. The port is configured by pin selections. Each 16-bit
output word of a stereo pair can be formatted within a 32-bit
field of a 64-bit frame as either right-justified, I2S compatible,
word clock controlled, or left-justified positions. Both 16-bit
samples can also be packed into a 32-bit frame, in left-justified
and I2S compatible positions.
The AD1870’s modulator was designed, simulated, and ex-
haustively tested to remain stable for any input within a wide
tolerance of its rated input range. The AD1870 is designed to
internally reset itself should it ever be overdriven, to prevent it
from going unstable. It will reset itself within 5 µs at a 48 kHz
sampling frequency after being overdriven. Overdriving the inputs
will produce a waveform “clipped” to plus or minus full scale.
The AD1870 is fabricated on a single monolithic integrated circuit
using a 0.5 µm CMOS double polysilicon, double metal process
and is offered in a plastic 28-lead SOIC package. Analog and
digital supply connections are separated to isolate the analog
circuitry from the digital supply and reduce digital crosstalk.
See TPCs 1 through 6 for illustrations of the AD1870’s typical
analog performance as measured by an Audio Precision System
One. Signal-to-(distortion + noise) is shown under a range of
conditions. Note that there is a small variance between the
AD1870 analog performance specifications and some of the
performance plots. This is because the Audio Precision System
One measures THD and noise over a 20 Hz to 24 kHz band-
width, while the analog performance is specified over a 20 Hz to
20 kHz bandwidth (i.e., the AD1870 performs slightly better
than the plots indicate). The power supply rejection graph (TPC 5)
illustrates the benefits of the AD1870’s internal differential ar-
chitecture. The excellent channel separation shown in TPC 6 is
the result of careful chip design and layout.
The AD1870 operates from a single 5 V power supply over the
temperature range of –40°C to +85°C and typically consumes
less than 260 mW of power.
THEORY OF OPERATION
⌺-⌬ Modulator Noise Shaping
The stereo, internally differential, analog modulator of the
AD1870 employs a proprietary feedforward and feedback archi-
tecture that passes input signals in the audio band with a unity
transfer function yet simultaneously shapes the quantization
noise generated by the one-bit comparator out of the audio
band (see Figure 1). Without the ⌺-⌬ architecture, this quanti-
zation noise would be spread uniformly from dc to one-half
the oversampling frequency, 64 × fS.
Digital Filter Characteristics
The digital decimator accepts the modulator’s stereo bit stream
and simultaneously performs two operations on it. First, the
decimator low-pass filters the quantization noise that the modu-
lator shaped to high frequencies and filters any other out-of-
audio-band input signals. Second, it reduces the data rate to an
output word rate equal to fS. The high frequency bit stream is
decimated to stereo 16-bit words at 48 kHz (or other desired
fS). The out-of-band one-bit quantization noise and other high
frequency components of the bit stream are attenuated by at
least 90 dB.
؉V
IN
DAC
MODULATOR
BITSTREAM
OUTPUT
V
IN
SINGLE-TO-
DIFFERENTIAL
CONVERTER
DAC
The AD1870 decimator implements a symmetric finite impulse
response (FIR) filter that possesses a linear phase response.
This filter achieves a narrow transition band (0.1 × fS), high
stop-band attenuation (>90 dB), and low pass-band ripple
(<0.006 dB). The narrow transition band allows the unattenu-
ated digitization of 20 kHz input signals with fS as low as
؊V
IN
Figure 1. Modulator Noise Shaper (One Channel)
–7–
REV. A
AD1870
44.1 kHz. The stop-band attenuation is sufficient to eliminate
modulator quantization noise from affecting the output. Low
pass-band ripple prevents the digital filter from coloring the
audio signal. See TPC 7 for the digital filter’s characteristics.
The output from the decimator is available as a single serial
output, multiplexed between left and right channels.
The AD1870 requires four external filter capacitors on Pins 11,
12, 17, and 18. These capacitors are used to filter the single-to-
differential converter outputs and are too large for practical
integration onto the die. They should be 470 pF NPO ceramic
chip type capacitors, as shown in Figure 3, placed as close to
the AD1870 package as possible.
Note that the digital filter itself is operating at 64 × fS. As a
consequence, Nyquist images of the pass-band, transition band,
and stop band will be repeated in the frequency spectrum at
multiples of 64 × fS. Thus the digital filter will attenuate to
greater than 90 dB across the frequency spectrum, except for a
window 0.55 × fS wide centered at multiples of 64 × fS. Any in-
put signals, clock noise, or digital noise in these frequency
windows will not be attenuated to the full 90 dB. If the high
frequency signals or noise appear within the pass-band images
within these windows, they will not be attenuated at all, and
input antialias filtering should therefore be applied.
Sample Clock
An external master clock supplied to CLKIN (Pin 28) drives
the AD1870 modulator, decimator, and digital interface. As
with any analog-to-digital conversion system, the sampling clock
must be low jitter to prevent conversion errors. If a crystal oscil-
lator is used as the clock source, it should be bypassed with a
0.1 µF capacitor, as shown below in Figure 3.
For the AD1870, the input clock operates at either 256 × fS or
384 × fS as selected by the 384/256 pin. When 384/256 is HI,
the 384 Mode is selected; when 384/256 is LO, the 256
Mode is selected. In both cases, the clock is divided down to
obtain the 64 × fS clock required for the modulator. The output
word rate itself will be at fS. This relationship is illustrated for
popular sample rates below:
Sample Delay
The sample delay or “group delay” of the AD1870 is dominated
by the processing time of the digital decimation filter. FIR filters
convolve a vector representing time samples of the input with
an equal-sized vector of coefficients. After each convolution, the
input vector is updated by adding a new sample at one end of
the “pipeline” and discarding the oldest input sample at the
other. For a FIR filter, the time at which a step input appears at
the output will be when that step input is halfway through
the input sample vector pipeline. The input sample vector
is updated every 64 × fS. The equation that expresses the
group delay for the AD1870 is:
256 Mode
CLKIN
384 Mode
CLKIN
Modulator
Sample Rate Rate
Output Word
12.288 MHz
11.2896 MHz 16.9344 MHz 2.822 MHz
8.192 MHz 12.288 MHz 2.048 MHz
18.432 MHz 3.072 MHz
48 kHz
44.1 kHz
32 kHz
The AD1870 serial interface will support both Master and Slave
Modes. Note that in Slave Mode it is required that the serial
interface clocks be externally derived from a common source.
In Master Mode, the serial interface clock outputs are internally
derived from CLKIN.
Group Delay (sec) = 36/fS (Hz)
For the most common sample rates, this can be summarized as:
fS
Group Delay
Reset, Autocalibration, and Power-Down
48 kHz
44.1 kHz
32 kHz
750 µs
816 µs
1125 µs
The active LO RESET pin (Pin 23) initializes the digital deci-
mation filter and clears the output data buffer. While in the reset
state, all digital pins defined as outputs of the AD1870 are
driven to ground (except for BCLK, which is driven to the state
defined by RDEDGE (Pin 6)). Analog Devices recommends
resetting the AD1870 on initial power-up so that the device is
properly calibrated. The reset signal must remain LO for the
minimum period specified in the Specifications section. The reset
pulse is asynchronous with respect to the master clock, CLKIN.
If, however, multiple AD1870s are used in a system, and it is
desired that they leave the reset state at the same time, the
common reset pulse should be made synchronous to CLKIN
(i.e., RESET should be brought HI on a CLKIN falling edge).
Due to the linear phase properties of FIR filters, the group
delay variation, or differences in group delay at different
frequencies, is essentially zero.
OPERATING FEATURES
Voltage Reference and External Filter Capacitors
The AD1870 includes a 2.25 V on-board reference that deter-
mines the AD1870’s input range. The left and right reference
pins (Pin 14 and Pin 15) should be bypassed with a 0.1 µF
ceramic chip capacitor in parallel with a 4.7 µF tantalum as
shown in Figure 3. Note that the chip capacitor should be clos-
est to the pin. The internal reference can be overpowered by
applying an external reference voltage at the VREFL (Pin 14) and
VREFR (Pin 15) pins, allowing multiple AD1870s to be calibrated
to the same gain. It is not possible to overpower the left and
right reference pins individually; the external reference voltage
should be applied to both Pin 14 and Pin 15. Note that the ref-
erence pins must still be bypassed as shown in Figure 3.
Multiple AD1870s can be synchronized to each other by using
a single master clock and a single reset signal to initialize all
devices. On coming out of reset, all AD1870s will begin sam-
pling at the same time. Note that in Slave Mode, the AD1870
is inactive (and all outputs are static, including WCLK) until
the first rising edge of LRCK after the first falling edge of
LRCK. This initial low going then high going edge of LRCK can
be used to “skew” the sampling start-up time of one AD1870
relative to other AD1870s in a system. In the data position con-
trolled by the WCLK Input Mode, WCLK must be HI with
LRCK HI, then WCLK HI with LRCK LO, then WCLK HI
with LRCK HI before the AD1870 starts sampling.
While it is possible to bypass each reference pin (VREFL and
VREFR) with a capacitor larger than the suggested 4.7 µF, it
is not recommended. A larger capacitor will have a longer
charge-up time, which may extend into the autocalibration period,
yielding incorrect results.
–8–
REV. A
AD1870
The AD1870 achieves its specified performance without the
need for user trims or adjustments. This is accomplished through
the use of on-chip automatic offset calibration that takes place
immediately following reset. This procedure nulls out any off-
sets in the single-to-differential converter, the analog modulator,
and the decimation filter. Autocalibration completes in approxi-
mately 8192 × (1/(FLRCK) seconds and need only be performed
once at power-up in most applications. (In Slave Mode, the 8192
cycles required for autocalibration do not start until after the
first rising edge of LRCK following the first falling edge of
LRCK.) The autocalibration scheme assumes that the inputs
are ac-coupled. DC-coupled inputs will work with the AD1870,
but the autocalibration algorithm will yield an incorrect offset
compensation.
APPLICATION ISSUES
Recommended Input Structure
The AD1870 input structure is single-ended to allow the board
designer to achieve a high level of functional integration. The
very simple recommended input circuit is shown in Figure 2. Note
the 1 µF ac-coupling capacitor, which allows input level shifting
for 5 V only operation and for autocalibration to properly null
offsets. The 3 dB point of the single-pole antialias RC filter is
240 kHz, which results in essentially no attenuation at 20 kHz.
Attenuation at 3 MHz is approximately 22 dB, which is adequate
to suppress fS noise modulation. If the analog inputs are exter-
nally ac-coupled, the 1 µF ac-coupling capacitors shown in
Figure 2 are not required.
The AD1870 also features a Power-Down Mode. It is enabled
by the active LO RESET Pin 23 (i.e., the AD1870 is in Power-
Down Mode while RESET is held LO). The power savings are
specified in the Specifications section. The converter is shut
down in the power-down state and will not perform conversions.
The AD1870 will be reset upon leaving the power-down state, and
autocalibration will commence after the RESET pin goes HI.
1F
300⍀
RIGHT
INPUT
V
R
IN
2.2nF
NPO
AD1870
1F
300⍀
LEFT
INPUT
V
L
IN
2.2nF
NPO
Power consumption can be further reduced by slowing down the
master clock input (at the expense of input pass band width).
Note that a minimum clock frequency, fCLKIN, is specified for
the AD1870.
Figure 2. Recommended Input Structure for Externally
DC-Coupled Inputs
Analog Input Voltage Swing
TAG Overrange Output
The single-ended input range of the analog inputs is specified in
relative terms in the Specifications section. The input level at
which clipping occurs linearly tracks the voltage reference
level; i.e., if the reference is high relative to the typical 2.25
V, the allowable input range without clipping is correspondingly
wider, and if the reference is low relative to the typical 2.25 V,
the allowable input range is correspondingly narrower.
The AD1870 includes a TAG serial output (Pin 27) that is pro-
vided to indicate status on the level of the input voltage. The
TAG output is at TTL compatible logic levels. A pair of unsigned
binary bits are output, synchronous with LRCK (MSB then
LSB), that indicate whether the current signal being converted
is: more than 1 dB under full scale, within 1 dB under full scale,
within 1 dB over full scale, or more than 1 dB over full scale.
The timing for the TAG output is shown in Figures 7–16. Note
that the TAG Bits are not “sticky”; i.e., they are not peak read-
ing, but rather change with every sample. Decoding of these two
bits is as follows:
Thus the maximum input voltage swing can be computed using
the following ratio:
2.25 V (Nominal Reference Voltage)
2.983 V p − p (Nominal Voltage Swing) Y V (Maximum Swing Without Clipping)
X V (Measured Reference Voltage)
=
TAG
MSB
Bits
LSB
Meaning
0
0
1
1
0
1
0
1
More than 1 dB under Full Scale
Within 1 dB under Full Scale
Within 1 dB over Full Scale
More Than 1 dB over Full Scale
–9–
REV. A
AD1870
Layout and Decoupling Considerations
Obtaining the best possible performance from the AD1870
requires close attention to board layout. Adhering to the follow-
ing principles will produce typical values of 92 dB dynamic range
and 90 dB S/(THD + N) in target systems. Schematics and lay-
out artwork of the AD1870 Evaluation Board, which implement
these recommendations, are available from Analog Devices.
CLKIN
TAG
LRCK
WCLK
BCLK
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SOUT
3
DV
2
DV
1
4
DIGITAL GROUND PLANE
DD
DD
The principles and their rationales are listed below. The first
two pertain to bypassing and are illustrated in Figure 3.
DGND1
RDEDGE
S/M
5
DGND2
RESET
MSBDLY
RLJUST
AGND
6
4.7F
0.1F
4.7F
0.1F
7
5V
DIGITAL
8
470pF
NPO
384/256
470pF
NPO
470pF
NPO
AV
DD
9
0.1F
AGNDL
CAPL2
V
L
V
R
CAPR2 CAPR1
AGNDR
REF
REF
V
L
10
V R
IN
IN
470pF
NPO
CAPR1
CAPR2
AGNDR
CAPL1 11
AD1870
CLKIN
OSCILLATOR
ANALOG GROUND PLANE
CAPL2
AGNDL
12
13
14
CAPL1
AGND AV
DV
1
DGND1 DGND2 DV
2
DD
DD
DD
V
R
V
L
REF
REF
0.1F
1F
10nF
10nF
1F
1F
Figure 4. Recommended Ground Plane
5V
5V
5V
DIGITAL
ANALOG DIGITAL
Each reference pin (Pin 14 and Pin 15) should be bypassed with
a 0.1 µF ceramic chip capacitor in parallel with a 4.7 µF tantalum
capacitor. The 0.1 µF chip cap should be placed as close to the
package pin as possible, and the trace to it from the reference
pin should be as short and as wide as possible. Keep this trace
away from any analog traces (Pins 10, 11, 12, 17, 18, 19). Cou-
pling between input and reference traces will cause even order
harmonic distortion. If the reference is needed somewhere else
on the printed circuit board, it should be shielded from any signal
dependent traces to prevent distortion.
Figure 3. Recommended Bypassing and Oscillator Circuits
There are two pairs of digital supply pins on opposite sides of
the part (Pins 4 and 5 and Pins 24 and 25). The user should tie
a bypass chip capacitor (10 nF ceramic) in parallel with a decou-
pling capacitor (1 µF tantalum) on each pair of supply pins as
close to the pins as possible. The traces between these package
pins and the capacitors should be as short and as wide as pos-
sible. This will prevent digital supply current transients from
being inductively transmitted to the inputs of the part.
Wherever possible, minimize the capacitive load on the digital
outputs of the part. This will reduce the digital spike currents
drawn from the digital supply pins and help keep the IC sub-
strate quiet.
Use a 0.1 µF chip analog capacitor in parallel with a 1.0 µF
tantalum capacitor from the analog supply (Pin 9) to the analog
ground plane. The trace between this package pin and the
capacitor should be as short and as wide as possible.
How to Extend SNR
The AD1870 should be placed on a split ground plane. The
digital ground plane should be placed under the top end of the
package, and the analog ground plane should be placed under
the bottom end of the package as shown in Figure 4. The split
should be between Pins 8 and 9 and between Pins 20 and 21.
The ground planes should be tied together at one spot under-
neath the center of the package with an approximately 3 mm
trace. This ground plane technique also minimizes RF transmis-
sion and reception.
A cost-effective method of improving the dynamic range and
SNR of an analog-to-digital conversion system is to use multiple
AD1870 channels in parallel with a common analog input. This
technique makes use of the fact that the noise in independent
modulator channels is uncorrelated. Thus every doubling of the
number of AD1870 channels used will improve the system dy-
namic range by 3 dB. The digital outputs from the correspond-
ing deci-mator channels must be arithmetically averaged to
obtain the improved results in the correct data format. A micro-
processor, either general purpose or DSP, can easily perform
the averaging operation.
–10–
REV. A
AD1870
Figure 5 shows a circuit for obtaining a 3 dB improvement in
dynamic range by using both channels of a single AD1870 with a
mono input. A stereo implementation would require using
two AD1870s and using the recommended input structure
shown in Figure 2. Note that a single microprocessor would likely
be able to handle the averaging requirements for both left and
right channels.
DIGITAL INTERFACE
Modes of Operation
The AD1870’s flexible serial output port produces data in
two’s-complement, MSB-first format. The input and output
signals are TTL logic-level compatible. Time multiplexed serial
data is output on SOUT (Pin 26), left channel then right chan-
nel, as determined by the left/right clock signal LRCK (Pin 1).
Note that there is no method for forcing the right channel to
precede the left channel. The port is configured by pin selections.
The AD1870 can operate in either Master or Slave Mode, with
the data in right-justified, I2S compatible, word clock controlled,
or left-justified positions.
V
R
AD1870
RECOMMENDED
INPUT BUFFER
IN
SINGLE
CHANNEL
OUTPUT
SINGLE
CHANNEL
INPUT
DIGITAL
AVERAGER
AD1870
V
L
IN
The various mode options are pin programmed with the S/M
(Slave/Master) Pin (7), the Right/Left Justify Pin (21), and the
MSBDLY Pin (22). The function of these pins is summarized
below.
Figure 5. Increasing Dynamic Range By Using Two
AD1870 Channels
S/M RLJUST MSBDLY WCLK
BCLK
LRCK
Serial Port Operation Mode
1
1
1
Output
Input
Input
Slave Mode. WCLK frames the data. The MSB is output on the
17th BCLK cycle. Provides right-justified data in slave mode
with a 64 × fS BCLK frequency. See Figure 7.
1
1
0
Input
Input
Input
Slave Mode. The MSB is output in the BCLK cycle after
WCLK is detected HI. WCLK is sampled on the BCLK active
edge, with the MSB valid on the next BCLK active edge. Tying
WCLK HI results in I2S-justified data. See Figure 8.
1
1
0
0
1
0
Output
Output
Input
Input
Input
Input
Slave Mode. Data left-justified with WCLK framing the data.
WCLK rises immediately after an LRCK transition. The MSB is
valid on the first BCLK active edge. See Figure 9.
Slave Mode. Data I2S-justified with WCLK framing the data.
WCLK rises in the second BCLK cycle after an LRCK transi-
tion. The MSB is valid on the second BCLK active edge. See
Figure 10.
0
0
1
1
1
0
Output
Output
Output Output
Output Output
Master Mode. Data right-justified. WCLK frames the data,
going HI in the 17th BCLK cycle. BCLK frequency = 64 × fS.
See Figure 11.
Master Mode. Data right-justified + 1. WCLK is pulsed in the
17th BCLK cycle, staying HI for only 1 BCLK cycle. BCLK
frequency = 64 × fS. See Figure 12.
0
0
0
0
1
0
Output
Output
Output Output
Output Output
Master Mode. Data left-justified. WCLK frames the data.
BCLK frequency = 64 × fS. See Figure 13.
Master Mode. Data I2S-justified. WCLK frames the data.
BCLK frequency = 64 × fS. See Figure 14.
–11–
REV. A
AD1870
Serial Port Data Timing Sequences
The LRCK HI for one BCLK period case is shown in Figures 15
and 16. With a one or two BCLK period HI pulse on LRCK,
note that both the left and right TAG Bits are output immedi-
ately, back to back. With a three-to-sixteen BCLK period HI pulse
on LRCK, the left TAG Bits are followed by one to fourteen
“dead” cycles, i.e., zeros, followed by the right TAG Bits. Also
note that WCLK stays HI continuously when the AD1870 is
in the 32-Bit Frame Mode. Figure 15 illustrates the left-justified
case, while Figure 16 illustrates the I2S-justified case.
The RDEDGE input (Pin 6) selects the bit clock (BCLK) polarity.
RDEDGE HI causes data to be transmitted on the BCLK falling
edge and valid on the BCLK rising edge; RDEDGE LO causes
data to be transmitted on the BCLK rising edge and valid on
the BCLK falling edge. This is shown in the serial data output
timing diagrams. The term “sampling” is used generically to
denote the BCLK edge (rising or falling) on which the serial data is
valid. The term “transmitting” is used to denote the other BCLK
edge. The S/M input (Pin 7) selects Slave Mode (S/M HI) or
Master Mode (S/M LO). Note that in Slave Mode, BCLK may be
continuous or gated, i.e., a stream of pulses during the data phase
followed by periods of inactivity between channels.
In all modes, the left and right channel data is updated with the
next sample within the last 1/8 of the current conversion cycle, i.e.,
within the last four BCLK cycles in 32-Bit Frame Mode, and
within the last eight BCLK cycles in 64-Bit Frame Mode. The
user must constrain the output timing such that the MSB of the
right channel is read before the final 1/8 of the current con-
version period.
In the Master Modes, the bit clock (BCLK), the left/right clock
(LRCK), and the word clock (WCLK) are always outputs, gen-
erated internally in the AD1870 from the master clock (CLKIN)
input. In Master Mode, a LRCK cycle defines a 64-bit “frame.”
LRCK is HI for a 32-bit “field” and LRCK is LO for a 32-
bit “field.”
Two modes deserve special discussion. The first special mode,
Slave Mode, Data Position Controlled by WCLK Input
(S/M = HI, RLJUST = HI, MSBDLY = LO), shown in
Figure 8, is the only mode in which WCLK is an input. The
16-bit output data-words can be placed at user-defined loca-
tions within 32-bit fields. The MSB will appear in the BCLK
period after WCLK is detected HI by the BCLK sampling edge.
If WCLK is HI during the first BCLK of the 32-bit field, i.e, if
WCLK is tied HI, then the MSB of the output word will be
valid on the sampling edge of the second BCLK. The effect is to
delay the MSB for one bit clock cycle into the field, making the
output data compatible at the data format level with the I2S data
format. Note that the relative placement of the WCLK input
can vary from 32-bit field to 32-bit field, even within the
same 64-bit frame. For example, within a single 64-bit frame,
the left word could be right-justified (by pulsing WCLK HI on
the 16th BCLK) and the right word could be in an I2S compat-
ible data format (by having WCLK HI at the beginning of the sec-
ond field).
In the Slave Modes, the bit clock (BCLK) and the left/right clock
(LRCK) are user-supplied inputs. The word clock (WCLK) is an
internally generated output, except when S/M is HI, RLJUST is
HI, and MSBDLY is LO when it is a user-supplied input that
controls the data position. Note that the AD1870 does not sup-
port asynchronous operation in Slave Mode; the clocks
(CLKIN, LRCK, BCLK, and WCLK) must be externally
derived from a common source. In general, CLKIN should be
divided down externally to create LRCK, BCLK, and WCLK.
In the Slave Modes, the relationship between LRCK and BCLK
is not fixed to the extent that there can be an arbitrary number
of BCLK cycles between the end of the data transmission and
the next LRCK transition. The Slave Mode timing diagrams are
therefore simplified as they show precise 32-bit fields and
64-bit frames.
In two Slave Modes, it is possible to pack two 16-bit samples in
a single 32-bit frame, as shown in Figures 15 and 16. BCLK,
LRCK, DATA, and TAG operate at one-half the frequency
(twice the period) as in the 64-bit frame modes. This 32-Bit
Frame Mode is enabled by pulsing the LRCK HI for a mini-
mum of one BCLK period to a maximum of 16 BCLK periods.
In the second special mode, Master Mode, Right-Justified
with MSB Delay, WCLK Pulsed in 17th BCLK Cycle (S/M
= LO, RLJUST = HI, MSBDLY = LO), shown in Figure 12,
WCLK is an output and is pulsed for one cycle by the AD1870.
The MSB is valid on the 18th BCLK sampling edge, and the
LSB extends into the first BCLK period of the next 32-bit field.
–12–
REV. A
AD1870
Timing Parameters
rates such as 48 × fS may result in an increased spectral noise
For master modes, a BCLK transmitting edge (labeled “XMIT”)
will be delayed from a CLKIN rising edge by tDLYCKB, as shown
in Figure 17. A LRCK transition will be delayed from a BCLK
transmitting edge by tDLYBLR. A WCLK rising edge will be
delayed from a BCLK transmitting edge by tDLYBWR, and a WCLK
falling edge will be delayed from a BCLK transmitting edge by
tDLYBWF. The DATA and TAG outputs will be delayed from a
floor, depending on the phase relationship of BCLK to CLKIN.
Synchronizing Multiple AD1870s
Multiple AD1870s can be synchronized by making all the
AD1870s serial port slaves. This option is illustrated in Figure 6.
See the Reset, Autocalibration, and Power-Down section for
additional information.
transmitting edge of BCLK by tDLYDT
.
CLOCK
SOURCE
For slave modes, an LRCK transition must be set up to a BCLK
sampling edge (labeled “SAMPLE”) by tSETLRBS (see Figure 18).
The DATA and TAG outputs will be delayed from an LRCK
transition by tDLYLRDT, and DATA and TAG outputs will be
delayed from BCLK transmitting edge by tDLYBDT. For Slave
Mode, Data Position Controlled by WCLK Input, WCLK must
#1 AD1870
DATA
BCLK
WCLK
LRCK
SLAVE MODE
RESET
CLKIN
be set up to a BCLK sampling edge by tSETWBS
.
For both Master and Slave Modes, BCLK must have a mini-
mum LO pulsewidth of tBPWL and a minimum HI pulsewidth of
#2 AD1870
DATA
BCLK
WCLK
LRCK
SLAVE MODE
tBPWH
.
RESET
CLKIN
The AD1870 CLKIN and RESET timing is shown in Figure 19.
CLKIN must have a minimum LO pulsewidth of tCPWL and a
minimum HI pulsewidth of tCPWH. The minimum period of
CLKIN is given by tCLKIN. RESET must have a minimum LO
pulsewidth of tRPWL. Note that there are no setup or hold time
requirements for RESET.
#N AD1870
DATA
BCLK
WCLK
LRCK
SLAVE MODE
RESET
CLKIN
Master Clock (CLKIN) Considerations
It is recommended that the BCLK and LRCK are derived from
CLKIN to ensure correct phase relationships. The modulator
of the AD1870 runs at 64 × fS. Therefore, best performance is
obtained when the BCLK rate equals 64 × fS or 32 × fS. BCLK
Figure 6. Synchronizing Multiple AD1870s
–13–
REV. A
AD1870
LRCK
INPUT
BCLK
RDEDGE = LO
31
32
1
2
15
16
17
18
19
32
1
2
15
16
17
18
19
32
1
2
INPUT
BCLK
RDEDGE = HI
PREVIOUS DATA
MSB-14 LSB
LEFT DATA
MSB
RIGHT DATA
MSB
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
LSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
MSB LSB
LEFT TAG
MSB LSB
TAG
OUTPUT
Figure 7. Serial Data Output Timing: Slave Mode, Right-Justified with No MSB Delay,
S/M = Hl, RLJUST = Hl, MSBDLY = Hl
LRCK
INPUT
BCLK
RDEDGE = LO
1
2
3
4
17
1
2
3
4
17
INPUT
BCLK
RDEDGE = HI
RIGHT DATA
MSB
LEFT DATA
MSB
SOUT
OUTPUT
ZEROS
ZEROS
LSB
ZEROS
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
INPUT
LEFT TAG
MSB
RIGHT TAG
MSB
TAG
OUTPUT
LSB
LSB
Figure 8. Serial Data Output Timing: Slave Mode, Data Position Controlled by WCLK Input,
S/M = Hl, RLJUST = Hl, MSBDLY = LO
LRCK
INPUT
BCLK
RDEDGE = LO
INPUT
31
32
1
2
3
4
16
17
18
31
32
1
2
3
4
16
17
18
BCLK
RDEDGE = HI
LEFT DATA
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
MSB
LSB
MSB
LSB
ZEROS
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
LSB
TAG
OUTPUT
MSB
Figure 9. Serial Data Output Timing: Slave Mode, Left-Justified with No MSB Delay, S/M = Hl,
RLJUST = LO, MSBDLY = Hl
–14–
REV. A
AD1870
LRCK
INPUT
BCLK
RDEDGE = LO
32
1
2
3
4
5
17
31
32
1
2
3
4
5
17
INPUT
BCLK
RDEDGE = HI
LEFT DATA
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
MSB
LSB
MSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
MSB
TAG
OUTPUT
LSB
Figure 10. Serial Data Output Timing: Slave Mode, I2S-Justified, S/M = Hl, RLJUST = LO, MSBDLY = LO
LRCK
OUTPUT
BCLK
RDEDGE = LO
31
32
1
2
15
16
17
18
19
32
1
2
15
16
17
18
19
32
1
2
OUTPUT
BCLK
RDEDGE = HI
PREVIOUS DATA
MSB-14 LSB
LEFT DATA
RIGHT DATA
MSB
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
MSB
LSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
MSB LSB
LEFT TAG
MSB
LSB
TAG
OUTPUT
Figure 11. Serial Data Output Timing: Master Mode, Right-Justified with No MSB Delay, S/M = LO,
RLJUST = Hl, MSBDLY = Hl
LRCK
OUTPUT
BCLK
RDEDGE = LO
OUTPUT
32
1
2
16
17
18
19
20
1
2
16
17
18
19
20
1
2
BCLK
RDEDGE = HI
PREVIOUS DATA
MSB-14 LSB
LEFT DATA
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
MSB
LSB
MSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
MSB LSB
TAG
OUTPUT
Figure 12. Serial Data Output Timing: Master Mode, Right-Justified with MSB Delay,
WCLK Pulsed in 17th BCLK Cycle, S/M = LO, RLJUST = Hl, MSBDLY = LO
–15–
REV. A
AD1870
LRCK
OUTPUT
BCLK
RDEDGE = LO
OUTPUT
31
32
1
2
3
16
17
18
31
32
1
2
3
16
17
18
BCLK
RDEDGE = HI
LEFT DATA
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
MSB
LSB
MSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
LSB
TAG
OUTPUT
MSB
Figure 13. Serial Data Output Timing: Master Mode, Left-Justified with No MSB Delay,
S/M = LO, RLJUST = LO, MSBDLY = Hl
LRCK
OUTPUT
BCLK
RDEDGE = LO
32
1
2
3
4
17
31
32
1
2
3
4
17
OUTPUT
BCLK
RDEDGE = HI
LEFT DATA
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
ZEROS
MSB
LSB
MSB
LSB
MSB-1 MSB-2
MSB-1 MSB-2
WCLK
OUTPUT
LEFT TAG
MSB LSB
RIGHT TAG
MSB
TAG
OUTPUT
LSB
Figure 14. Serial Data Output Timing: Master Mode, I2S-Justified, S/M = LO, RLJUST = LO,
MSBDLY = LO
LRCK
INPUT
BCLK
RDEDGE = LO
31
32
1
2
3
4
5
16
17
18
19
20
21
32
1
2
INPUT
BCLK
RDEDGE = HI
PREVIOUS DATA
LSB
MSB-14
LEFT DATA
MSB-1 MSB-2 MSB-3 MSB-4
RIGHT DATA
LEFT DATA
MSB
SOUT
OUTPUT
MSB
LSB
MSB
LSB
MSB-1 MSB-2 MSB-3 MSB-4
MSB-1
WCLK
OUTPUT
HI
HI
LEFT TAG
MSB
LSB
RIGHT TAG
LSB
LEFT TAG
TAG
OUTPUT
MSB
MSB
LSB
Figure 15. Serial Data Output Timing: Slave Mode, Left-Justified with No MSB Delay,
32-Bit Frame Mode, S/M = Hl, RLJUST = LO, MSBDLY = Hl
–16–
REV. A
AD1870
LRCK
INPUT
BCLK
RDEDGE = LO
32
1
2
3
4
5
6
17
18
19
20
21
22
1
2
3
INPUT
BCLK
RDEDGE = HI
PREVIOUS DATA
LSB
MSB-14
LEFT DATA
MSB-1 MSB-2 MSB-3 MSB-4
RIGHT DATA
LEFT DATA
MSB
SOUT
OUTPUT
MSB
LSB
MSB
LSB
MSB-1 MSB-2 MSB-3 MSB-4
MSB-1
WCLK
OUTPUT
HI
HI
LEFT TAG
MSB
RIGHT TAG
MSB LSB
LEFT TAG
MSB
RIGHT TAG
LSB MSB
TAG
OUTPUT
LSB
Figure 16. Serial Data Output Timing: Slave Mode, I2S-Justified, 32-Bit Frame Mode,
S/M = Hl, RLJUST = LO, MSBDLY = LO
CLKIN
INPUT
tDLYCKB
BCLK OUTPUT (64 x fS
RDEDGE = LO
BCLK OUTPUT (64 x fS
)
tBPWL
XMIT
XMIT
XMIT
XMIT
tBPWH
)
RDEDGE = HI
tBPWH
tBPWL
LRCK
OUTPUT
tDLYBWR
tDLYBWF
tDLYBLR
WCLK
OUTPUT
tDLYDT
DATA AND TAG
OUTPUTS
Figure 17. Master Mode Clock Timing
tBPWL
tBPWH
BCLK INPUT
RDEDGE = LO
XMIT
SAMPLE
XMIT
SAMPLE
BCLK OUTPUT
RDEDGE = HI
tBPWH
tSETLRBS
tBPWL
LRCK
INPUT
tSETWBS
WCLK
INPUT
tDLYBDT
tDLYLRDT
DATA AND TAG
OUTPUTS
MSB
MSB-1
Figure 18. Slave Mode Clock Timing
tCLKIN
tCPWH
CLKIN INPUT
tCPWL
RESET INPUT
tRPWL
Figure 19. CLKIN and RESET Timing
–17–
REV. A
AD1870
OUTLINE DIMENSIONS
R-28 (S-Suffix)
28-Lead Wide-Body SO
SOL-28
Dimensions shown in inches and (millimeters)
28
15
0.2992 (7.60)
0.2914 (7.40)
0.4193 (10.65)
PIN 1
0.3937 (10.00)
14
1
0.1043 (2.65)
0.7125 (18.10)
0.0926 (2.35)
0.0291 (0.74)
0.6969 (17.70)
x 45°
0.0098 (0.25)
0.0500 (1.27)
0.0157 (0.40)
8
؇
؇
0.0118 (0.30)
0.0040 (0.10)
0
0.0500 (1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.0125 (0.32)
0.0091 (0.23)
AD1870–Revision History
Location
Page
6/02—Data Sheet changed from REV. 0 to REV. A.
Edit to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
–18–
REV. A
–19–
–20–
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