a
AD1896
*
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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. Trademarks and
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Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © 2003 Analog Devices, Inc. All rights reserved.
REV. A
192 kHz Stereo Asynchronous
Sample Rate Converter
FUNCTIONAL BLOCK DIAGRAM
GRPDLYS VDD_IO
VDD_CORE
SERIAL
INPUT
FIFO
FS
OUT
FS
IN
SERIAL
OUTPUT
DIGITAL
PLL
FIR
FILTER
CLOCK DIVIDER
ROM
AD1896
BYPASS
MUTE_O
MUTE_I
SDATA_I
SCLK_I
LRCLK_I
SMODE_IN_0
SMODE_IN_1
SMODE_IN_2
MCLK_I
MCLK_O
MSMODE_0
MSMODE_2
MSMODE_1
WLNGTH_O_0
WLNGTH_O_1
SMODE_O_0
SMODE_O_1
TDM_IN
SDATA_O
SCLK_O
LRCLK_O
RESET
PRODUCT OVERVIEW
The AD1896 is a 24-bit, high performance, single-chip, second-
generation asynchronous sample rate converter. Based on Analog
Devices experience with its first asynchronous sample rate
converter, the AD1890, the AD1896 offers improved performance
and additional features. This improved performance includes a
THD + N range of –117 dB to –133 dB depending on the sample
rate and input frequency, 142 dB (A-Weighted) dynamic range,
192 kHz sampling frequencies for both input and output sample
rates, improved jitter rejection, and 1:8 upsampling and 7.75:1
downsampling ratios. Additional features include more serial
formats, a bypass mode, better interfacing to digital signal pro-
cessors, and a matched-phase mode.
The AD1896 has a 3-wire interface for the serial input and
output ports that supports left-justified, I
2
S, and right-justified
(16-, 18-, 20-, 24-bit) modes. Additionally, the serial output
port supports TDM mode for daisy-chaining multiple AD1896s to
a digital signal processor. The serial output data is dithered down
to 20, 18, or 16 bits when 20-, 18-, or 16-bit output data is se-
lected. The AD1896 sample rate converts the data from the
serial input port to the sample rate of the serial output port. The
sample rate at the serial input port can be asynchronous with
respect to the output sample rate of the output serial port. The
master clock to the AD1896, MCLK, can be asynchronous to
both the serial input and output ports.
MCLK can be generated either off-chip or on-chip by the AD1896
master clock oscillator. Since MCLK can be asynchronous to the
input or output serial ports, a crystal can be used to generate
MCLK internally to reduce noise and EMI emissions on the
board. When MCLK is synchronous to either the output or input
serial port, the AD1896 can be configured in a master mode where
MCLK is divided down and used to generate the left/right
and bit clocks for the serial port that is synchronous to MCLK.
The AD1896 supports master modes of 256 ¥ f
S
, 512 ¥ f
S
,
and 768 ¥ f
S
for both input and output serial ports.
Conceptually, the AD1896 interpolates the serial input data by
a rate of 2
20
and samples the interpolated data stream by the
output sample rate. In practice, a 64-tap FIR filter with 2
20
polyphases, a FIFO, a digital servo loop that measures the time
difference between the input and output samples within 5 ps,
and a digital circuit to track the sample rate ratio are used to
perform the interpolation and output sampling. Refer to the
Theory of Operation section. The digital servo loop and sample
rate ratio circuit automatically track the input and output
sample rates.
(Continued on Page 17)
FEATURES
Automatically Senses Sample Frequencies
No Programming Required
Attenuates Sample Clock Jitter
3.3 V–5 V Input and 3.3 V Core Supply Voltages
Accepts 16-/18-/20-/24-Bit Data
Up to 192 kHz Sample Rate
Input/Output Sample Ratios from 7.75:1 to 1:8
Bypass Mode
Multiple AD1896 TDM Daisy-Chain Mode
Multiple AD1896 Matched-Phase Mode
142 dB Signal-to-Noise and Dynamic Range
(A-Weighted, 20 Hz–20 kHz BW)
Up to –133 dB THD + N
Linear Phase FIR Filter
Hardware Controllable Soft Mute
Supports 256 f
S
, 512 f
S
, or 768 f
S
Master
Mode Clock
Flexible 3-Wire Serial Data Port with Left-Justified,
I
2
S, Right-Justified (16-,18-, 20-, 24-Bits), and
TDM Serial Port Modes
Master/Slave Input and Output Modes
28-Lead SSOP Plastic Package
APPLICATIONS
Home Theater Systems, Studio Digital Mixers,
Automotive Audio Systems, DVD, Set-Top Boxes,
Digital Audio Effects Processors, Studio-to-Transmitter
Links, Digital Audio Broadcast Equipment,
DigitalTape Varispeed Applications
*Patents pending.
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