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Datasheet: AD1870 (Analog Devices)

Single-supply 16-bit Stereo Adc

 

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Analog Devices

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FUNCTIONAL BLOCK DIAGRAM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
L
RCK
WCLK
BCLK
DGND1
DV
DD
1
RDEDGE
S/
M
384/
256
AV
DD
V
IN
L
CAPL1
CAPL2
AGNDL
V
REF
L
CLKIN
TAG
SOUT
DV
DD
2
RESET
MSBDLY
R
LJUST
AGND
V
IN
R
CAPR1
CAPR2
AGNDR
V
REF
R
SERIAL OUTPUT
INTERFACE
THREE-STAGE FIR
DECIMATION
FILTER
DGND2
THREE-STAGE FIR
DECIMATION
FILTER
CLOCK
DIVIDER
VOLTAGE
REFERENCE
DAC
SINGLE-TO-
DIFFERENTIAL INPUT
CONVERTER
SINGLE-TO-
DIFFERENTIAL INPUT
CONVERTER
AD1870
DAC
DAC
DAC
REV. 0
a
Single-Supply
16-Bit - Stereo ADC
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 Passband Ripple
Fourth-Order, 64 Oversampling - Modulator
Three-Stage, Linear-Phase Decimator
256 f
S
or 384 f
S
Input Clock
Less than 100 W (Typ) Power-Down Mode
Input Overrange Indication
On-Chip Voltage Reference
Flexible Serial Output Interface
28-Lead SOIC Package
APPLICATIONS
Consumer Digital Audio Receivers
Digital Audio Recorders, Including Portables
CD-R, DCC, MD, and DAT
Multimedia and Consumer Electronics Equipment
Sampling Music Synthesizers
AD1870*
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.
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
f
S
single-bit
output data rate to an f
S
word rate. They provide linear phase
and a narrow transition band that properly digitizes 20 kHz signals
at a 44.1 kHz sampling frequency. Passband ripple is less than
0.006 dB, and stop band attenuation exceeds 90 dB.
(Continued on Page 7)
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. 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
www.analog.com
Fax: 781/326-8703
Analog Devices, Inc., 2001
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
interface. The AD1870 accepts a 256
f
S
or a 384
f
S
input
clock (f
S
is the sampling frequency) and operates in both serial
port "master" and "slave" modes. In slave mode, all clocks must
be externally derived from a common source.
Input signals are sampled at 64
f
S
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 passband. The on-chip single-ended to differential signal
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 differen-
tial switched-capacitor
- modulator architecture shapes the
*Protected by U.S. Patent Numbers 5055843, 5126653; others pending.
AD1870SPECIFICATIONS
REV. 0
2
TEST CONDITIONS UNLESS OTHERWISE NOTED
Supply Voltages
5.0
V
Ambient Temperature
25
C
Input Clock (f
CLKIN
) [256
f
S
]
12.288
MHz
Input Signal
991.768
Hz
0.5
dB Full Scale
Measurement Bandwidth
23.2 Hz to 19.998 kHz
Load Capacitance on Digital Outputs
50
pF
Input Voltage HI (V
IH
)
2.4
V
Input Voltage LO (V
IL
)
0.8
V
Master Mode, Data I
2
S-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
89
93
dB
With A-Weight Filter
92
96
dB
Signal to (THD + Noise)
86.5
90.5
dB
Signal to THD
94
dB
Analog Inputs
Single-Ended Input Range (
Full Scale)*
V
REF
1.49
V
Input Impedance at Each Input Pin
32
k
V
REF
2.05
2.25
2.55
V
DC Accuracy
Gain Error
0.5
2.5
%
Interchannel Gain Mismatch
0.05
dB
Gain Drift
115
ppm/
C
Midscale Offset Error (After Calibration)
3
20
LSBs
Midscale Drift
0.2
LSB/
C
Crosstalk (EIAJ Method)
110
100
dB
*V
IN
p-p = V
REF
1.326.
Minimum Input
V
V
Maximum Input
V
V
REF
REF
REF
REF
=
=
+








.
.
1 326
2
1 326
2
DIGITAL I/O
Min
Typ
Max
Unit
Input Voltage HI (V
IH
)
2.4
V
Input Voltage LO (V
IL
)
0.8
V
Input Leakage (I
IH
@ V
IH
= 5 V)
10
A
Input Leakage (I
IL
@ V
IL
= 0 V)
10
A
Output Voltage HI (V
OH
@ I
OH
= 2 mA)
2.4
V
Output Voltage LO (V
OL
@ I
OL
= 2 mA)
0.4
V
Input Capacitance
15
pF
DIGITAL TIMING (Guaranteed over 40
C to +85C, DV
DD
= AV
DD
= 5 V
5%. Refer to Figures 1719.)
Min
Typ
Max
Unit
t
CLKIN
CLKIN Period
48
81
780
ns
f
CLKIN
CLKIN Frequency (1/t
CLKIN
)
1.28
12.288
20.48
MHz
t
CPWL
CLKIN LO Pulsewidth
15
ns
t
CPWH
CLKIN HI Pulsewidth
15
ns
t
RPWL
RESET LO Pulsewidth
50
ns
t
BPWL
BCLK LO Pulsewidth
15
ns
t
BPWH
BCLK HI Pulsewidth
15
ns
t
DLYCKB
CLKIN Rise to BCLK Xmit (Master Mode)
15
ns
t
DLYBLR
BCLK Xmit to L
RCK Transition (Master Mode)
15
ns
t
DLYBWR
BCLK Xmit to WCLK Rise
10
ns
t
DLYBWF
BCLK Xmit to WCLK Fall
10
ns
t
DLYDT
BCLK Xmit to DATA/TAG Valid (Master Mode)
10
ns
t
SETLRBS
L
RCK Setup to BCLK Sample (Slave Mode)
10
ns
t
DLYLRDT
L
RCK Transition to DATA/TAG Valid (Slave Mode)
No MSB Delay Mode (for MSB Only)
40
ns
t
SETWBS
WCLK Setup to BCLK Sample (Slave Mode)
Data Position Controlled by WCLK Input Mode
10
ns
t
DLYBDT
BCLK Xmit to DATA/TAG Valid (Slave Mode)
All Bits Except MSB in No MSB Delay Mode
All Bits in MSB Delay Mode
40
ns
POWER
Min
Typ
Max
Unit
Supplies
Voltage, Analog and Digital
4.75
5
5.25
V
Analog Current
43
52
mA
Analog Current--Power Down (CLKIN Running)
25
A
Digital Current
9.3
12
mA
Digital Current--Power Down (CLKIN Running)
50
A
Dissipation
Operation--Both Supplies
263
315
mW
Operation--Analog Supply
216
260
mW
Operation--Digital Supply
47
55
mW
Power Down--Both Supplies (CLKIN Running)
375
W
Power Down--Both Supplies (CLKIN Not Running)
375
W
Power Supply Rejection (See TPC 5)
1 kHz 300 mV p-p Signal at Analog Supply Pins
90
dB
20 kHz 300 mV p-p Signal at Analog Supply Pins
68
dB
Stop Band (>0.55
f
S
)--any 300 mV p-p Signal
110
dB
AD1870
REV. 0
3
TEMPERATURE RANGE
Min
Typ
Max
Unit
Specifications Guaranteed
25
C
Functionality Guaranteed
40
+85
C
Storage
60
+100
C
DIGITAL FILTER CHARACTERISTICS
Min
Typ
Max
Unit
Decimation Factor
64
Passband Ripple
0.006
dB
Stop Band
1
Attenuation
90
dB
48 kHz f
S
(at Recommended Crystal Frequencies)
Passband
0
21.6
kHz
Stop Band
26.4
kHz
44.1 kHz f
S
(at Recommended Crystal Frequencies)
Passband
0
20
kHz
Stop Band
24.25
kHz
32 kHz f
S
(at Recommended Crystal Frequencies)
Passband
0
14.4
kHz
Stop Band
17.6
kHz
Other f
S
Passband
0
0.45
f
S
Stop Band
0.55
f
S
Group Delay
36/f
S
s
Group Delay Variation
0
s
NOTES
1
Stop band repeats itself at multiples of 64
f
S
, where f
S
is the output word rate. Thus the digital filter will attenuate to 0 dB across the frequency spectrum except
for a range
0.55 f
S
wide at multiples of 64
f
S
.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS
Min
Typ
Max
Unit
DV
DD
1 to DGND1 and DV
DD
2 to DGND2
0
6
V
AV
DD
to AGND/AGNDL/AGNDR
0
6
V
Digital Inputs
DGND 0.3
DV
DD
+ 0.3
V
Analog Inputs
AGND 0.3
AV
DD
+ 0.3
V
AGND to DGND
0.3
+0.3
V
Reference Voltage
Indefinite Short Circuit to Ground
Soldering (10 sec)
300
C
ORDERING GUIDE
Package
Package
Model
Temperature
Description
Option
AD1870JR
40
C to +85C
SOIC
R-28
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
AD1870SPECIFICATIONS
4
REV. 0
AD1870
REV. 0
5
PIN FUNCTION DESCRIPTIONS
Input/
Pin
Pin
Output
Name
Description
1
I/O
L
RCK
Left/
Right Clock
2
I/O
WCLK
Word Clock
3
I/O
BCLK
Bit Clock
4
I
DV
DD
1
5 V Digital Supply
5
I
DGND1
Digital Ground
6
I
RDEDGE
Read Edge Polarity Select
7
I
S/
M
Slave/
Master Select
8
I
384/
256
Clock Mode
9
I
AV
DD
5 V Analog Supply
10
I
V
IN
L
Left Channel Input
11
O
CAPL1
Left External Filter Capacitor 1
12
O
CAPL2
Left External Filter Capacitor 2
13
I
AGNDL
Left Analog Ground
14
O
V
REF
L
Left Reference Voltage Output
15
O
V
REF
R
Right Reference Voltage Output
16
I
AGNDR
Right Analog Ground
17
O
CAPR2
Right External Filter Capacitor 2
18
O
CAPR1
Right External Filter Capacitor 1
19
I
V
IN
R
Right Channel Input
20
I
AGND
Analog Ground
21
I
R
LJUST
Right/
Left Justify
22
I
MSBDLY
Delay MSB One BCLK Period
23
I
RESET
Reset
24
I
DGND2
Digital Ground
25
I
DV
DD
2
5 V Digital Supply
26
O
SOUT
Serial Data Output
27
O
TAG
Serial Overrange Output
28
I
CLKIN
Master Clock
DEFINITIONS
Dynamic Range
The ratio of a full-scale output signal to the integrated output
noise in the passband (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 har-
monics are below the noise with a 60 dB input, so the noise
level establishes the dynamic range. The dynamic range is speci-
fied with and without an A-Weight filter applied.
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 passband, expressed in decibels (dB).
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
passband, expressed in decibels.
Passband
The region of the frequency spectrum unaffected by the attenu-
ation of the digital decimator's filter.
Passband Ripple
The peak-to-peak variation in amplitude response from equal-
amplitude input signal frequencies within the passband,
expressed in decibels.
Stop Band
The region of the frequency spectrum attenuated by the digi-
tal decimator's filter to the degree specified by "stop band
attenuation."
Gain Error
With a near full-scale input, the ratio of actual output to
expected output, expressed as a percentage.
Interchannel Gain Mismatch
With identical near full-scale inputs, the ratio of outputs of the
two stereo channels, expressed in decibels.
Gain Drift
Change in response to a near full-scale input with a change in
temperature, expressed as parts-per-million (ppm) per
C.
Midscale Offset Error
Output response to a midscale dc input, expressed in least-
significant bits (LSBs).
Midscale Drift
Change in midscale offset error with a change in temperature,
expressed as parts-per-million (ppm) per
C.
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.
Power Supply Rejection
With no analog input, signal present at the output when a
300 mV p-p signal is applied to power supply pins, expressed in
decibels of full scale.
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
The difference in group delays at different input frequencies.
Specified as the difference between largest and the smallest
group delays in the passband, expressed in microseconds (
s).
AD1870
REV. 0
6
24
2
0
22
20
18
16
14
12
10
8
6
4
FREQUENCY kHz
0
140
80
120
100
20
60
40
dB
F
S
TPC 1. 1 kHz Tone at 0.5 dBFS (16k-Point FFT)
0
140
24
80
120
2
100
0
20
60
40
22
20
18
16
14
12
10
8
6
4
FREQUENCY kHz
dB
F
S
TPC 2. 1 kHz Tone at 10 dBFS (16k-Point FFT)
FREQUENCY kHz
dB
F
S
80
100
20
94
98
2
96
0
88
92
90
86
84
82
18
16
14
12
10
8
6
4
TPC 3. THD + N vs.Frequency at 0.5 dBFS
AMPLITUDE dBFS
dB
F
S
80
100
94
98
2
96
0
88
92
90
86
84
82
18
16
14
12
10
8
6
4
TPC 4. THD + N vs. Amplitude at 1 kHz
AMPLITUDE kHz
dB
F
S
60
100
20
95
2
0
80
90
85
75
70
65
18
16
14
12
10
8
6
4
TPC 5. Power Supply Rejection to 300 mV p-p on AV
DD
FREQUENCY kHz
dB
F
S
80
20
115
2
120
0
100
105
95
90
85
18
16
14
12
10
8
6
4
110
TPC 6. Channel Separation vs. Frequency at 0.5 dBFS
Typical Performance Characteristics
AD1870
REV. 0
7
(
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, I
2
S-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 I
2
S-compatible positions.
The AD1870 is fabricated on a single monolithic integrated circuit
using a 0.5
m 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 cir-
cuitry from the digital supply and reduce digital crosstalk.
The AD1870 operates from a single 5 V power supply over the
temperature range of 40
C to +85C, 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 quantiza-
tion noise would be spread uniformly from dc to one-half the
oversampling frequency, 64
f
S
.
DAC
DAC
SINGLE-TO-
DIFFERENTIAL
CONVERTER
MODULATOR
BITSTREAM
OUTPUT
V
IN
V
IN
V
IN
Figure 1. Modulator Noise-Shaper (One Channel)
- 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.
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 f
S
and its higher multiples.
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 indirect dependence on temperature and time as
it affects dc offset. The AD1870 suppresses idle tones 20 dB or
better below the integrated noise floor.
The AD1870's modulator was designed, simulated, and exhaus-
tively 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
s at a 48 kHz sampling
frequency after being overdriven. Overdriving the inputs will
produce a waveform "clipped" to plus or minus full scale.
See TPCs 1 through 16 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 (TPC 5)
graph illustrates the benefits of the AD1870's internal differen-
tial architecture. The excellent channel separation shown in
TPC 6 is the result of careful chip design and layout.
Digital Filter Characteristics
The digital decimator accepts the modulator's stereo bitstream
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 f
S
. The high frequency bitstream is
decimated to stereo 16-bit words at 48 kHz (or other desired
f
S
). The out-of-band one-bit quantization noise and other high
frequency components of the bitstream are attenuated by at
least 90 dB.
The AD1870 decimator implements a symmetric Finite Impulse
Response (FIR) filter which possesses a linear phase response.
This filter achieves a narrow transition band (0.1
f
S
), high
stop band attenuation (> 90 dB), and low passband ripple
(< 0.006 dB). The narrow transition band allows the unattenu-
ated digitization of 20 kHz input signals with f
S
as low as
dB
F
S
0
80
1.0
60
70
0.1
0.0
40
50
30
20
10
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
110
90
100
NORMALIZED
f
S
120
10
TPC 7. Digital Filter Signal Transfer Function to f
S
AD1870
REV. 0
8
44.1 kHz. The stop band attenuation is sufficient to eliminate
modulator quantization noise from affecting the output. Low
passband 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.
Note that the digital filter itself is operating at 64
f
S
. As a
consequence, Nyquist images of the passband, transition band,
and stop band will be repeated in the frequency spectrum at
multiples of 64
f
S
. Thus the digital filter will attenuate to
greater than 90 dB across the frequency spectrum, except for a
window
0.55 f
S
wide centered at multiples of 64
f
S
. Any
input 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 passband images
within these windows, they will not be attenuated at all, and
therefore input antialias filtering should be applied.
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 half-way through
the input sample vector pipeline. The input sample vector
is updated every 64
f
S
. The equation that expresses the
group delay for the AD1870 is:
Group Delay (sec) = 36/f
S
(Hz)
For the most common sample rates this can be summarized as:
f
S
Group Delay
48 kHz
750
s
44.1 kHz
816
s
32 kHz
1125
s
Due to the linear phase properties of FIR filters, the group
delay variation, or differences in group delay at different fre-
quencies, 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 (14 and 15) should be bypassed with a 0.1
F ceramic chip
capacitor in parallel with a 4.7
F tantalum as shown in Figure
3. Note that the chip capacitor should be closest to the pin. The
internal reference can be overpowered by applying an external
reference voltage at the V
REF
L (Pin 14) and V
REF
R (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 reference pins must still
be bypassed as shown in Figure 3.
While it is possible to bypass each reference pin (V
REF
L and
V
REF
R) with a capacitor larger than the suggested 4.7
F, it is
not recommended. A larger capacitor will have a longer charge-
up time, which may extend into the autocalibration period, yield-
ing incorrect results.
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.
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
F capacitor, as shown below in Figure 3.
For the AD1870, the input clock operates at either 256
f
S
or
384
f
S
as selected by the 384/
256 pin. When 384/256 is HI,
the 384 mode is selected, and when 384/
256 is LO, the 256
mode is selected. In both cases, the clock is divided down to
obtain the 64
f
S
clock required for the modulator. The output
word rate itself will be at f
S
. This relationship is illustrated for
popular sample rates below:
256 Mode
384 Mode
Modulator
Output Word
CLKIN
CLKIN
Sample Rate Rate
12.288 MHz
18.432 MHz
3.072 MHz
48 kHz
11.2896 MHz
16.9344 MHz 2.822 MHz
44.1 kHz
8.192 MHz
12.288 MHz
2.048 MHz
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.
Reset, Autocalibration, and Power-Down
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 "Specifications" above. 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).
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 L
RCK after the first falling edge of LRCK.
This initial low-going then high-going edge of L
RCK can be used
to "skew" the sampling start-up time of one AD1870 relative to
other AD1870s in a system. In the Data Position Controlled by
WCLK Input mode, WCLK must be HI with L
RCK HI, then
WCLK HI with L
RCK LO, then WCLK HI with LRCK HI
before the AD1870 starts sampling.
AD1870
REV. 0
9
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/(F
L
R
CK
) 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 L
RCK following the first falling edge of
L
RCK.) 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.
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 speci-
fied in the "Specifications'' section above. 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.
Power consumption can be further reduced by slowing down the
master clock input (at the expense of input passband width).
Note that a minimum clock frequency, f
CLKIN
, is specified for
the AD1870.
Tag Overrange Output
The AD1870 includes a TAG serial output (Pin 27) which is
provided 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 L
RCK (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 TPCs 7 through 16.
Note that the TAG bits are not "sticky"; i.e., they are not peak
reading, but rather change with every sample. Decoding of these
two bits is as follows:
TAG
Bits
MSB,
LSB
Meaning
0
0
More Than 1 dB Under Full Scale
0
1
Within 1 dB Under Full Scale
1
0
Within 1 dB Over Full Scale
1
1
More Than 1 dB Over Full Scale
APPLICATIONS 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
F 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 f
S
noise modulation. If the analog inputs are exter-
nally ac-coupled, the 1
F ac-coupling capacitors shown in
Figure 2 are not required.
AD1870
V
IN
R
V
IN
L
LEFT
INPUT
RIGHT
INPUT
300
2.2nF
NPO
1 F
300
2.2nF
NPO
1 F
Figure 2. Recommended Input Structure for Externally
DC-Coupled Inputs
Analog Input Voltage Swing
The single-ended input range of the analog inputs is specified in
relative terms in the "Specifications" section of this data sheet.
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 corre-
spondingly wider; if the reference is low relative to the typical
2.25 V, the allowable input range is correspondingly narrower.
Thus the maximum input voltage swing can be computed using
the following ratio:
2 25
2 983
.
(
)
.
(
)
(
)
(
)
V
reference voltage
V p p
voltage swing
X Volts measured reference voltage
Y Volts
swing without clipping
nominal
nominal
maximum
-
=
AD1870
REV. 0
10
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.
The principles and their rationales are listed below. The first
two pertain to bypassing and are illustrated in Figure 3.
5V
ANALOG
5V
DIGITAL
5V
DIGITAL
AD1870
CAPL2
CAPL1
CLKIN
AGND
AV
DD
DV
DD
1 DGND1 DGND2 DV
DD
2
470pF
NPO
AGNDL V
REF
L V
REF
R AGNDR CAPR2
CAPR1
470pF
NPO
OSCILLATOR
5V
DIGITAL
10nF
470pF
NPO
470pF
NPO
10nF
1 F
0.1 F
1 F
1 F
0.1 F
4.7 F
0.1 F
4.7 F
0.1 F
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
decoupling capacitor (1
F 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 possible. This will prevent digital supply current transients
from being inductively transmitted to the inputs of the part.
Use a 0.1
F chip analog capacitor in parallel with a 1.0 F
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.
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.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
L
RCK
WCLK
BCLK
DGND1
DV
DD
1
RDEDGE
S/
M
384/
256
AV
DD
V
IN
L
CAPL1
CAPL2
AGNDL
V
REF
L
CLKIN
TAG
SOUT
DV
DD
2
RESET
MSBDLY
R
LJUST
AGND
V
IN
R
CAPR1
CAPR2
AGNDR
V
REF
R
DGND2
DIGITAL GROUND PLANE
ANALOG GROUND PLANE
Figure 4. Recommended Ground Plane
Each reference pin (14 and 15) should be bypassed with a 0.1
F
ceramic chip capacitor in parallel with a 4.7
F tantalum capaci-
tor. The 0.1
F chip cap should be placed as close to the pack-
age 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)
. Coupling
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.
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.
How to Extend SNR
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 system dynamic
range by 3 dB. The digital outputs from the corresponding deci-
mator channels have to be arithmetically averaged to obtain the
improved results in the correct data format. A microprocessor,
either general-purpose or DSP, can easily perform the averaging
operation.
AD1870
REV. 0
11
Shown in Figure 5 is a circuit for obtaining a 3 dB improve-
ment 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.
AD1870
RECOMMENDED
INPUT BUFFER
SINGLE
CHANNEL
INPUT
DIGITAL
AVERAGER
AD1870
V
IN
R
V
IN
L
SINGLE
CHANNEL
OUTPUT
Figure 5. Increasing Dynamic Range By Using Two
AD1870 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 sig-
nals 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 L
RCK (Pin 1).
Note that there is no method for forcing the right channel to
precede the left channel. The port is configured by pin selec-
tions. The AD1870 can operate in either master or slave mode,
with the data in right-justified, I
2
S-compatible, Word Clock
controlled or left-justified positions.
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
as follows:
S/
M RLJUST
MSBDLY
WCLK
BCLK
L
RCK
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
f
S
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 I
2
S-justified data. See Figure 8.
1
0
1
Output
Input
Input
Slave Mode. Data left-justified with WCLK framing the data.
WCLK rises immediately after an L
RCK transition. The MSB is
valid on the first BCLK active edge. See Figure 9.
1
0
0
Output
Input
Input
Slave Mode. Data I
2
S-justified with WCLK framing the data.
WCLK rises in the second BCLK cycle after an L
RCK transi-
tion. The MSB is valid on the second BCLK active edge. See
Figure 10.
0
1
1
Output
Output
Output
Master Mode. Data right-justified. WCLK frames the data,
going HI in the 17th BCLK cycle. BCLK frequency = 64
f
S
.
See Figure 11.
0
1
0
Output
Output
Output
Master Mode. Data right-justified + 1. WCLK is pulsed in the
17th BCLK cycle, staying HI for only 1 BCLK cycle. BCLK
frequency = 64
f
S
. See Figure 12.
0
0
1
Output
Output
Output
Master Mode. Data left-justified. WCLK frames the data.
BCLK frequency = 64
f
S
. See Figure 13.
0
0
0
Output
Output
Output
Master Mode. Data I
2
S-justified. WCLK frames the data.
BCLK frequency = 64
f
S
. See Figure 14.
AD1870
REV. 0
12
Serial Port Data Timing Sequences
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 the master modes, the bit clock (BCLK), the left/right clock
(L
RCK), and the word clock (WCLK) are always outputs, gen-
erated internally in the AD1870 from the master clock (CLKIN)
input. In master mode, a L
RCK cycle defines a 64-bit "frame."
L
RCK is HI for a 32-bit "field" and LRCK is LO for a 32-
bit "field."
In the slave modes, the bit clock (BCLK), and the left/right clock
(L
RCK) 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,
L
RCK, BCLK and WCLK) must be externally derived from a
common source. In general, CLKIN should be divided down
externally to create L
RCK, BCLK, and WCLK.
In the slave modes, the relationship between L
RCK 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 L
RCK 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,
L
RCK, 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 L
RCK HI for a minimum
of one BCLK period to a maximum of sixteen BCLK periods.
The L
RCK HI for one BCLK period case is shown in Fig-
ures 15 and 16. With a one or two BCLK period HI pulse on
L
RCK, note that both the left and right TAG bits are output
immediately, back-to-back. With a three-to-sixteen BCLK period
HI pulse on L
RCK, 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 I
2
S-justified case.
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 4 BCLK cycles in 32-bit frame mode, and within
the last 8 BCLK cycles in 64-bit frame mode). The user must con-
strain the output timing such that the MSB of the right channel
is read before the final 1/8 of the current conversion period.
Two modes deserve special discussion. The first special mode,
"Slave Mode, Data Position Controlled by WCLK Input" (S/
M
= HI, R
LJUST = 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 locations 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 dur-
ing the first BCLK of the 32-bit field (if WCLK is tied HI for
example), 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 I
2
S data for-
mat. 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 I
2
S-compatible data
format (by having WCLK HI at the beginning of the second field).
In the second special mode "Master Mode, Right-Justified
with MSB Delay, WCLK Pulsed in 17th Cycle" (S/
M = LO,
R
LJUST = 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.
AD1870
REV. 0
13
Timing Parameters
For master modes, a BCLK transmitting edge (labeled "XMIT")
will be delayed from a CLKIN rising edge by t
DLYCKB
, as shown
in Figure 17. A L
RCK transition will be delayed from a BCLK
transmitting edge by t
DLYBLR
. A WCLK rising edge will be
delayed from a BCLK transmitting edge by t
DLYBWR
, and a WCLK
falling edge will be delayed from a BCLK transmitting edge by
t
DLYBWF
. The DATA and TAG outputs will be delayed from a
transmitting edge of BCLK by t
DLYDT
.
For slave modes, an L
RCK transition must be setup to a BCLK
sampling edge (labeled "SAMPLE") by t
SETLRBS
. The DATA
and TAG outputs will be delayed from an L
RCK transition by
t
DLYLRDT
, and DATA and TAG outputs will be delayed from
BCLK transmitting edge by t
DLYBDT
. For "Slave Mode, Data
Position Controlled by WCLK Input," WCLK must be set up
to a BCLK sampling edge by t
SETWBS
.
For both master and slave modes, BCLK must have a minimum
LO pulsewidth of t
BPWL
, and a minimum HI pulsewidth of t
BPWH
.
The AD1870 CLKIN and
RESET timing is shown in Figure
19. CLKIN must have a minimum LO pulsewidth of t
CPWL
, and
a minimum HI pulsewidth of t
CPWH
. The minimum period of
CLKIN is given by t
CLKIN
.
RESET must have a minimum LO
pulsewidth of t
RPWL
. Note that there are no setup or hold time
requirements for
RESET.
Master Clock (CLKIN) Considerations
It is recommended that the BCLK and L
RCK are derived from
CLKIN to ensure correct phase relationships. The modulator
of the AD1870 runs at 64
f
S
, therefore best performance is
obtained when the BCLK rate equals 64
f
S
or 32
f
S
. BCLK
rates such as 48
f
S
may result in an increased spectral noise
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.
#1 AD1870
SLAVE MODE
CLKIN
DATA
BCLK
WCLK
L
RCK
CLOCK
SOURCE
#2 AD1870
SLAVE MODE
CLKIN
DATA
BCLK
WCLK
L
RCK
#N AD1870
SLAVE MODE
CLKIN
DATA
BCLK
WCLK
L
RCK
RESET
RESET
RESET
Figure 6. Synchronizing Multiple AD1870s
AD1870
REV. 0
14
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
31
32
1
2
15
16
17
18
19
32
1
2
15
16
17
18
19
32
1
2
MSB-14
LSB
PREVIOUS DATA
MSB-1
LEFT DATA
MSB-2
LSB
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
MSB-1 MSB-2
LSB
ZEROS
WCLK
OUTPUT
TAG
OUTPUT
MSB
LSB
LEFT TAG
MSB
LSB
RIGHT TAG
MSB
LSB
LEFT TAG
L
RCK
INPUT
INPUT
MSB
MSB
Figure 7. Serial Data Output Timing: Slave Mode, Right-Justified with No MSB Delay,
S/
M = Hl, RLJUST = Hl, MSBDLY = Hl
BCLK
RDEDGE= LO
BCLK
RDEDGE = HI
MSB-1
LEFT DATA
MSB-2
LSB
SOUT
OUTPUT
ZEROS
RIGHT DATA
MSB-1 MSB-2
LSB
ZEROS
WCLK
INPUT
TAG
OUTPUT
MSB
LEFT TAG
MSB
RIGHT TAG
ZEROS
1
2
3
4
17
1
2
3
4
17
INPUT
L
RCK
INPUT
MSB
LSB
MSB
LSB
Figure 8. Serial Data Output Timing: Slave Mode, Data Position Controlled by WCLK Input,
S/
M = Hl, RLJUST= Hl, MSBDLY = LO
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
31
32
1
2
3
4
16
SOUT
OUTPUT
WCLK
OUTPUT
TAG
OUTPUT
LSB
LEFT TAG
LSB
RIGHT TAG
31
32
1
2
3
4
16
MSB-1
LEFT DATA
MSB-2
LSB
MSB
MSB-1
RIGHT DATA
MSB-2
LSB
ZEROS
ZEROS
ZEROS
INPUT
L
RCK
INPUT
17
18
17
18
MSB
MSB
MSB
Figure 9. Serial Data Output Timing: Slave Mode, Left-Justified with No MSB Delay, S/
M = Hl,
R
LJUST = LO, MSBDLY = Hl
AD1870
REV. 0
15
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
32
1
2
3
4
17
SOUT
OUTPUT
WCLK
OUTPUT
TAG
OUTPUT
MSB
LEFT TAG
MSB
RIGHT TAG
31
32
1
2
3
4
17
MSB-1
LEFT DATA
MSB-2
LSB
MSB-1
RIGHT DATA
MSB-2
LSB
ZEROS
ZEROS
ZEROS
INPUT
L
RCK
INPUT
5
5
MSB
LSB
MSB
LSB
Figure 10. Serial Data Output Timing: Slave Mode, I
2
S-Justified, S/
M = Hl, RLJUST = LO, MSBDLY = LO
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
31
32
1
2
15
16
17
18
19
32
1
2
15
16
17
18
19
32
1
2
MSB-14
LSB
PREVIOUS DATA
MSB-1
LEFT DATA
MSB-2
LSB
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
MSB-1 MSB-2
LSB
ZEROS
WCLK
OUTPUT
TAG
OUTPUT
MSB
LSB
LEFT TAG
MSB
LSB
RIGHT TAG
MSB
LSB
LEFT TAG
OUTPUT
L
RCK
OUTPUT
MSB
MSB
Figure 11. Serial Data Output Timing: Master Mode, Right-Justified with No MSB Delay, S/
M = LO,
R
LJUST = Hl, MSBDLY = Hl
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
32
1
2
16
17
18
19
1
2
16
17
18
19
20
1
2
MSB-14
LSB
PREVIOUS DATA
MSB-1
LEFT DATA
MSB-2
LSB
RIGHT DATA
SOUT
OUTPUT
ZEROS
ZEROS
MSB-1 MSB-2
LSB
ZEROS
WCLK
OUTPUT
TAG
OUTPUT
MSB
LSB
LEFT TAG
MSB
LSB
RIGHT TAG
20
L
RCK
OUTPUT
OUTPUT
MSB
MSB
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
AD1870
REV. 0
16
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
31
32
1
2
3
16
SOUT
OUTPUT
WCLK
OUTPUT
TAG
OUTPUT
LSB
LEFT TAG
LSB
RIGHT TAG
31
32
1
2
3
16
MSB-1
LEFT DATA
MSB-2
LSB
MSB-1
RIGHT DATA
MSB-2
LSB
ZEROS
ZEROS
ZEROS
L
RCK
OUTPUT
OUTPUT
17
18
17
18
MSB
MSB
MSB
MSB
Figure 13. Serial Data Output Timing: Master Mode, Left-Justified with No MSB Delay,
S/
M = LO, RLJUST = LO, MSBDLY = Hl
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
32
1
2
3
4
17
SOUT
OUTPUT
WCLK
OUTPUT
TAG
OUTPUT
MSB
LEFT TAG
MSB
RIGHT TAG
31
32
1
2
3
4
17
MSB-1
LEFT DATA
MSB-2
LSB
MSB-1
RIGHT DATA
MSB-2
LSB
ZEROS
ZEROS
ZEROS
OUTPUT
L
RCK
OUTPUT
MSB
LSB
MSB
LSB
Figure 14. Serial Data Output Timing: Master Mode, I
2
S-Justified, S/
M = LO, RLJUST = LO,
MSBDLY = LO
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
31
32
1
2
3
4
16
SOUT
OUTPUT
WCLK
OUTPUT
TAG
OUTPUT
19
20
21
32
1
2
INPUT
HI
HI
5
17
18
LSB
LEFT TAG
MSB
LSB
RIGHT TAG
LEFT TAG
LSB
MSB-14
LSB
PREVIOUS DATA
MSB-1 MSB-2 MSB-3
LEFT DATA
MSB-4
MSB-3 MSB-4
LSB
MSB-1 MSB-2
RIGHT DATA
LSB
MSB-1
LEFT DATA
L
RCK
INPUT
MSB
MSB
MSB
MSB
MSB
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
AD1870
REV. 0
17
BCLK
RDEDGE = LO
BCLK
RDEDGE = HI
32
1
2
3
4
5
17
SOUT
OUTPUT
TAG
OUTPUT
20
21
22
1
2
3
INPUT
WCLK
OUTPUT
HI
HI
6
18
19
MSB
LEFT TAG
MSB
LSB
RIGHT TAG
MSB-14
LSB
PREVIOUS DATA
MSB-1 MSB-2 MSB-3
LEFT DATA
MSB-4
MSB-3 MSB-4
LSB
MSB-1 MSB-2
RIGHT DATA
LSB
MSB-1
LEFT DATA
MSB
LEFT TAG
MSB
RIGHT TAG
L
RCK
INPUT
MSB
LSB
MSB
MSB
LSB
Figure 16. Serial Data Output Timing: Slave Mode, I
2
S-Justified, 32-Bit Frame Mode,
S/
M = Hl, RLJUST= LO, MSBDLY = LO
BCLK OUTPUT (64 x
f
S
)
RDEDGE = LO
CLKIN
INPUT
BCLK OUTPUT (64 x
f
S
)
RDEDGE = HI
WCLK
OUTPUT
DATA & TAG
OUTPUTS
t
DLYCKB
t
BPWL
t
BPWH
t
BPWL
t
BPWH
t
DLYBLR
t
DLYDT
t
DLYBWR
t
DLYBWF
L
RCK
OUTPUT
XMIT
XMIT
XMIT
XMIT
Figure 17. Master Mode Clock Timing
WCLK
INPUT
DATA & TAG
OUTPUTS
XMIT
SAMPLE
SAMPLE
t
BPWL
t
BPWH
t
BPWH
t
BPWL
t
DLYLRDT
MSB
MSB-1
t
DLYBDT
t
SETLRBS
BCLK INPUT
RDEDGE = LO
BCLK OUTPUT
RDEDGE = HI
L
RCK
INPUT
XMIT
t
SETWBS
Figure 18. Slave Mode Clock Timing
CLKIN INPUT
RESET INPUT
t
CPWH
t
CPWL
t
CLKIN
t
RPWL
Figure 19. CLKIN and
RESET Timing
AD1870
REV. 0
18
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
R-28 (S-Suffix)
28-Lead Wide-Body SO
SOL-28
PIN 1
0.2992 (7.60)
0.2914 (7.40)
0.4193 (10.65)
0.3937 (10.00)
1
28
15
14
0.0125 (0.32)
0.0091 (0.23)
0.0500 (1.27)
0.0157 (0.40)
8
0
0.0291 (0.74)
0.0098 (0.25)
x 45
0.0192 (0.49)
0.0138 (0.35)
0.0500 (1.27)
BSC
0.1043 (2.65)
0.0926 (2.35)
0.7125 (18.10)
0.6969 (17.70)
0.0118 (0.30)
0.0040 (0.10)
19
C009442.54/01(0)
PRINTED IN U.S.A.
20
© 2018 • ICSheet
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