AD1895

The AD1895 which based upon analog devices, Inc. experience with its first asynchronous sample rate converter, the AD1890, the AD1895 offers improved performance and additional features is a 24-bit, high-performance, single-chip, second generation asynchronous sample rate converter. The AD1895 has a 3-wire interface for the serial input andoutput ports that supports left-justified, I2S, and right-justified(16-, 18-, 20-, 24-bit) modes. Additionally, the serial outputport supports TDM mode for daisy chaining multiple AD1895s to a digital signal processor. The serial output data is dithered downto 20, 18 or 16 bits when 20-, 18- or 16-bit output data is selected.The AD1895 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 AD1895, MCLK, can be asynchronous to both the serial input and output ports. This improved performance includes a THD + N range of -115 dB to -122 dB depending on sample rate and input frequency, 128 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, and better interfacing to digital signal processors.

The features of AD1895 can be summarized as (1)automatically senses sample frequencies; (2)no programming required; (3)attenuates sample clock jitter; (4)3.3 V-5 Input and 3.3 core supply voltages; (5)accepts 16-/18-/20-/24-bit data; (6)Up to 192 kHz sample rate; (7)input/output sample ratios from 7.75:1 to 1:8; (8)bypass made; (9)multiple AD1895 TDM daisy-chain mode; (10)128 dB signal-to-noise and dynamic range (A-weighted, 20 Hz-20 kHz BW); (11)up to -122 dB THD +N; (12)linear phase FIR filter; (13)hardware controllable soft mute; (14)supports 256 fs, 512 fs or 768 fs master made cluck; (15)flexible three-wire serial data port with left-justified, I2S. rightjustified 15-. 20-. 24-bits). and TDM serial port modes; (16)master/slave input and output modes; (17)28-Lead SSOP plastic package.

The absolute maximum ratings of AD1895 are (1)supply voltages VDD_CORE: 3.3 V, VDD_IO: 5.0 V or 3.3 V; (2)ambient temperature: 25°C; (3)input clock: 30.0 MHz; (4)input signal: 1.000 kHz, 0 dBFS; (5)measurement bandwidth: 20 to fS_OUT/2 Hz; (6)word width: 24 Bits; (7)load capacitance: 50 pF; (8)input voltage HI: 2.4 V; (9)input voltage LO: 0.8 V.