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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 ؋ fS, 512 ؋ fS or 768 ؋ fS Master Mode
Clock
Flexible Three-Wire Serial Data Port with Left-Justified,
I2S, 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, Digital
Tape Varispeed Applications
PRODUCT OVERVIEW
The AD1896 is a 24-bit, high-performance, single-chip, secondgeneration asynchronous sample rate converter. Based upon
Analog Devices Inc. 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 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 processors, and a matched phase mode.
The AD1896 has a 3-wire interface for the serial input and
output ports that supports left-justified, I2S, and right-justified
(16-, 18-, 20-, 24-bit) modes. Additionally, the serial output
192 kHz Stereo Asynchronous
Sample Rate Converter
AD1896*
FUNCTIONAL BLOCK DIAGRAM
RESET
GRPDLYS
VDD_IO VDD_CORE
AD1896
MUTE_I
SDATA_I
SCLK_I
LRCLK_I
SMODE_IN_0
SMODE_IN_1
SMODE_IN_2
FSOUT
FIFO
SDATA_O
SCLK_O
LRCLK_O
FSIN
SERIAL
INPUT
TDM_IN
DIGITAL
PLL
BYPASS
FIR
FILTER
SERIAL
OUTPUT
SMODE_O_0
SMODE_O_1
MUTE_O
CLOCK DIVIDER
MCLK_I
MSMODE_0
MCLK_O
ROM
WLNGTH_O_0
WLNGTH_O_1
MSMODE_2
MSMODE_1
port supports TDM mode for daisy chaining multiple AD1896’s 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 selected.
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 either be generated 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 × fS, 512 × fS and
768 × fS for both input and output serial ports.
Conceptually, the AD1896 interpolates the serial input data by
a rate of 220 and samples the interpolated data stream by the
output sample rate. In practice, a 64-tap FIR filter with 220
polyphases, a FIFO, a digital servo loop that measures the time
difference between 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 15)
*Patents pending.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
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© Analog Devices, Inc., 2001
