a 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, 64ⴛ Oversampling ⌺-⌬ Modulator Three-Stage, Linear-Phase Decimator 256 ⴛ fS or 384 ⴛ fS 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 Single-Supply 16-Bit ⌺-⌬ Stereo ADC AD1870* FUNCTIONAL BLOCK DIAGRAM LRCK 1 WCLK 2 BCLK 3 DVDD1 4 DGND1 5 RDEDGE 6 SERIAL OUTPUT INTERFACE THREE-STAGE FIR DECIMATION FILTER DAC DAC CLOCK DIVIDER THREE-STAGE FIR DECIMATION FILTER DAC DAC 28 CLKIN 27 TAG 26 SOUT 25 DVDD2 24 DGND2 23 RESET 22 MSBDLY S/M 7 384/256 8 21 RLJUST 9 20 AGND VINL 10 19 VINR CAPL1 11 18 CAPR1 17 CAPR2 16 AGNDR 15 VREFR AVDD CAPL2 12 AGNDL 13 VREFL 14 SINGLE-TODIFFERENTIAL INPUT CONVERTER SINGLE-TODIFFERENTIAL INPUT CONVERTER VOLTAGE REFERENCE 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 interface. 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 externally derived from a common source. Input signals are sampled at 64 × fS onto internally buffered switched capacitors, eliminating external sample-and-hold amplifiers 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 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 differential switched-capacitor ⌺-⌬ modulator architecture *Protected by U.S. Patent Numbers 5055843, 5126653; others pending. 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. 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. (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, 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., 2002 AD1870–SPECIFICATIONS TEST CONDITIONS UNLESS OTHERWISE NOTED Supply Voltages Ambient Temperature Input Clock (fCLKIN) [256 × fS] Input Signal 5.0 V 25 °C 12.288 MHz 991.768 Hz –0.5 dB Full Scale Measurement Bandwidth 23.2 Hz to 19.998 kHz Load Capacitance on Digital Outputs 50 pF 2.4 V Input Voltage HI (VIH) Input Voltage LO (VIL) 0.8 V 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 Resolution 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 Analog Inputs Single-Ended Input Range (± Full Scale)* Input Impedance at Each Input Pin VREF DC Accuracy Gain Error Interchannel Gain Mismatch Gain Drift Midscale Offset Error (After Calibration) Midscale Drift Crosstalk (EIAJ Method) 89 92 86.5 2.05 Typ Max Unit 16 Bits 93 96 90.5 94 dB dB dB dB VREF ± 1.49 32 2.25 V kΩ V ± 0.5 0.05 115 ±3 –0.2 –110 2.55 ⴞ2.5 ⴞ20 –100 % dB ppm/°C LSBs LSB/°C dB *VIN p-p = VREF × 1.326. Minimum Input = VREF V – REF × 1.326 VREF × 1.326 Maximum Input = VREF + 2 2 –2– REV. A AD1870 DIGITAL I/O Min 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 Typ Max Unit 2.4 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.) tCLKIN fCLKIN tCPWL tCPWH tRPWL tBPWL tBPWH tDLYCKB tDLYBLR tDLYBWR tDLYBWF tDLYDT tSETLRBS tDLYLRDT tSETWBS tDLYBDT CLKIN Period CLKIN Frequency (1/tCLKIN) CLKIN LO Pulsewidth CLKIN HI Pulsewidth RESET LO Pulsewidth BCLK LO Pulsewidth BCLK HI Pulsewidth CLKIN Rise to BCLK Xmit (Master Mode) BCLK Xmit to LRCK Transition (Master Mode) BCLK Xmit to WCLK Rise 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 Min Typ Max Unit 48 1.28 15 15 50 15 15 81 12.288 780 20.48 ns MHz ns ns ns ns ns ns ns ns ns ns ns 15 15 10 10 10 10 40 10 ns ns 40 ns POWER Supplies Voltage, Analog and Digital Analog Current Analog Current–Power-Down (CLKIN Running) Digital Current Digital Current–Power-Down (CLKIN Running) Dissipation 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 REV. A Min Typ Max Unit 4.75 5 43 25 9.3 50 5.25 52 V mA µA mA µA 263 216 47 375 375 90 68 110 –3– 12 315 260 55 mW mW mW µW µW dB dB dB AD1870 TEMPERATURE RANGE Min Specifications Guaranteed Functionality Guaranteed Storage Typ Max Unit +85 +100 °C °C °C +25 –40 –60 DIGITAL FILTER CHARACTERISTICS Min Decimation Factor Pass-Band Ripple Stop-Band* Attenuation 48 kHz fS (at Recommended Crystal Frequencies) Pass Band Stop Band 44.1 kHz fS (at Recommended Crystal Frequencies) Pass Band Stop Band 32 kHz fS (at Recommended Crystal Frequencies) Pass Band Stop Band Other fS Pass Band Stop Band Group Delay Group Delay Variation Typ Max Unit 0.006 dB dB 0 26.4 21.6 kHz kHz 0 24.25 20 kHz kHz 0 17.6 14.4 kHz kHz 0 0.55 0.45 fS fS s µs 64 90 36/fS 0 *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 DVDD1 to DGND1 and DVDD2 to DGND2 AVDD to AGND/AGNDL/AGNDR Digital Inputs Analog Inputs AGND to DGND Reference Voltage Soldering (10 sec) Min Typ Max Unit 0 0 DGND – 0.3 AGND – 0.3 –0.3 +6 +6 DVDD + 0.3 AVDD + 0.3 +0.3 Indefinite Short Circuit to Ground +300 V V V V V °C ORDERING GUIDE Model Temperature Package Description Package Option AD1870AR –40°C to +85°C SOIC R-28 AD1870AR–REEL –40°C to +85°C SOIC R-28 in 13” Reel (1000 pcs.) EVAL-AD1870EB 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. –4– WARNING! ESD SENSITIVE DEVICE REV. A AD1870 PIN FUNCTION DESCRIPTIONS Pin Input/ Output Pin Name Description 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 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 I I O O I LRCK WCLK BCLK DVDD1 DGND1 RDEDGE S/M 384/256 AVDD VINL CAPL1 CAPL2 AGNDL VREFL VREFR AGNDR CAPR2 CAPR1 VINR AGND RLJUST MSBDLY RESET DGND2 DVDD2 SOUT TAG CLKIN Left/Right Clock Word Clock Bit Clock 5 V Digital Supply Digital Ground Read Edge Polarity Select 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 Analog Ground Right/Left Justify Delay MSB One BCLK Period Reset Digital Ground 5 V Digital Supply Serial Data Output Serial Overrange Output Master Clock 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. Pass Band The region of the frequency spectrum unaffected by the attenuation of the digital decimator’s filter. Pass-Band Ripple The peak-to-peak variation in amplitude response from equalamplitude input signal frequencies within the pass band, expressed in decibels. Stop Band The region of the frequency spectrum attenuated by the digital 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 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, expressed 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 without 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 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). (S/(THD + N)) The ratio of the root-mean-square (rms) value of the fundamental input signal to the rms sum of all other spectral components in the pass band, expressed in decibels. REV. A –5– AD1870–Typical Performance Characteristics –80 0 –82 –20 –84 –40 –86 –88 d BFS dBFS –60 –80 –90 –92 –94 –100 –96 –120 –98 –100 –60 –140 0 2 4 6 8 10 12 14 16 FREQUENCY – kHz 18 20 22 24 –50 –40 –30 –20 –10 –0.5 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) 0 –60 –20 –65 –70 –40 –75 d BFS dBFS –60 –80 –80 –85 –100 –90 –120 –95 –100 –140 0 2 4 6 8 10 12 14 16 18 20 22 0 24 2 4 6 FREQUENCY – kHz 8 10 12 14 FREQUENCY – kHz 16 18 20 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 –80 –82 –85 –84 –90 –86 –95 d BFS d BFS –88 –90 –92 –100 –105 –94 –110 –96 –115 –98 –100 0 –120 2 4 6 8 10 12 14 16 18 0 20 FREQUENCY – kHz 2 4 6 8 10 12 14 FREQUENCY – kHz 16 18 20 TPC 6. Channel Separation vs. Frequency at –0.5 dBFS TPC 3. THD + N vs. Frequency at –0.5 dBFS –6– REV. A AD1870 ⌺-⌬ 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 resonator 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 0 –10 –20 –30 d BFS –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 NORMALIZED fS 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. 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 exhaustively 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 bandwidth, 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 architecture. 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 architecture 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 quantization 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 modulator shaped to high frequencies and filters any other out-ofaudio-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. ⴙVIN DAC VIN MODULATOR BITSTREAM OUTPUT SINGLE-TODIFFERENTIAL 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 unattenuated digitization of 20 kHz input signals with fS as low as ⴚVIN Figure 1. Modulator Noise Shaper (One Channel) REV. A –7– 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-todifferential 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 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 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 oscillator 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 48 kHz 44.1 kHz 32 kHz 750 µs 816 µs 1125 µs 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. For the most common sample rates, this can be summarized as: Group Delay Modulator Output Word Sample Rate Rate 12.288 MHz 18.432 MHz 3.072 MHz 11.2896 MHz 16.9344 MHz 2.822 MHz 8.192 MHz 12.288 MHz 2.048 MHz Group Delay (sec) = 36/fS (Hz) fS 384 Mode CLKIN Reset, Autocalibration, and Power-Down The active LO RESET pin (Pin 23) initializes the digital decimation 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 determines 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 closest 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 reference 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 sampling 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 controlled 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 offsets in the single-to-differential converter, the analog modulator, and the decimation filter. Autocalibration completes in approximately 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 externally 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 PowerDown 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. 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. 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 REV. A VINR 2.2nF NPO AD1870 LEFT INPUT 1F 300⍀ VINL 2.2nF NPO Figure 2. Recommended Input Structure for Externally DC-Coupled Inputs 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 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 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 reading, but rather change with every sample. Decoding of these two bits is as follows: Bits LSB 1F 300⍀ Analog Input Voltage Swing TAG Overrange Output TAG MSB RIGHT INPUT Thus the maximum input voltage swing can be computed using the following ratio: 2.25 V ( Nominal Reference Voltage) X V ( Measured Reference Voltage) = 2.983 V p − p ( Nominal Voltage Swing ) Y V ( Maximum Swing Without Clipping ) –9– AD1870 Layout and Decoupling Considerations Obtaining the best possible performance from the AD1870 requires close attention to board layout. Adhering to the following principles will produce typical values of 92 dB dynamic range and 90 dB S/(THD + N) in target systems. Schematics and layout 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. 4.7F 4.7F 0.1F 0.1F 470pF NPO 470pF NPO AGNDL VREFL VREFR AGNDR CAPR2 470pF NPO 470pF NPO CAPR1 5V DIGITAL 28 CLKIN WCLK 2 27 TAG BCLK 3 26 SOUT DVDD1 4 DGND1 5 24 DGND2 RDEDGE 6 23 RESET S/M 7 22 MSBDLY 384/256 8 21 RLJUST AVDD 9 20 AGND VINL 10 19 VINR 18 CAPR1 17 CAPR2 AGNDL 13 16 AGNDR VREFL 14 15 VREFR OSCILLATOR CAPL2 12 AVDD DVDD1 DGND1 DGND2 DVDD2 0.1F 10nF 10nF 1F 1F 1F 5V 5V ANALOG DIGITAL DIGITAL GROUND PLANE CAPL1 11 CLKIN CAPL1 AGND 1 25 DVDD2 0.1F CAPL2 AD1870 LRCK ANALOG GROUND PLANE Figure 4. Recommended Ground Plane 5V DIGITAL 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 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 possible. This will prevent digital supply current transients from being inductively transmitted to the inputs of the part. 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. 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 underneath the center of the package with an approximately 3 mm trace. This ground plane technique also minimizes RF transmission and reception. 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). 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 substrate 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 the system dynamic range by 3 dB. The digital outputs from the corresponding deci-mator channels must 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. –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. SINGLE CHANNEL INPUT AD1870 RECOMMENDED INPUT BUFFER VINR AD1870 DIGITAL AVERAGER SINGLE CHANNEL OUTPUT VINL 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 signals are TTL logic-level compatible. Time multiplexed serial data is output on SOUT (Pin 26), left channel then right channel, 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. 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. 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 0 1 Output 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. 1 0 0 Output Input Input Slave Mode. Data I2S-justified with WCLK framing the data. WCLK rises in the second BCLK cycle after an LRCK transition. 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 × fS. 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 × fS. See Figure 12. 0 0 1 Output Output Output Master Mode. Data left-justified. WCLK frames the data. BCLK frequency = 64 × fS. See Figure 13. 0 0 0 Output Output Output Master Mode. Data I2S-justified. WCLK frames the data. BCLK frequency = 64 × fS. See Figure 14. REV. A –11– AD1870 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 (LRCK), and the word clock (WCLK) are always outputs, generated 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 32bit “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 support 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 minimum of one BCLK period to a maximum of 16 BCLK periods. 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 immediately, 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. 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 conversion period. 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 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 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 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 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 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 transmitting edge of BCLK by tDLYDT. rates such as 48 × fS 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. 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 be set up to a BCLK sampling edge by tSETWBS. For both Master and Slave Modes, BCLK must have a minimum LO pulsewidth of tBPWL and a minimum HI pulsewidth of tBPWH. 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. CLOCK SOURCE #1 AD1870 SLAVE MODE DATA RESET BCLK WCLK CLKIN LRCK #2 AD1870 SLAVE MODE RESET DATA BCLK WCLK CLKIN LRCK #N AD1870 SLAVE MODE Master Clock (CLKIN) Considerations RESET DATA BCLK WCLK 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 CLKIN LRCK REV. A –13– Figure 6. Synchronizing Multiple AD1870s AD1870 LRCK INPUT BCLK RDEDGE = LO 31 INPUT 32 1 2 15 16 17 18 19 32 1 2 15 16 17 18 19 32 1 2 BCLK RDEDGE = HI PREVIOUS DATA SOUT OUTPUT MSB-14 RIGHT DATA LEFT DATA ZEROS LSB MSB LSB ZEROS MSB MSB-1 MSB-2 LSB ZEROS MSB-1 MSB-2 WCLK OUTPUT LEFT TAG TAG OUTPUT MSB RIGHT TAG LSB MSB LEFT TAG LSB MSB LSB 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 INPUT 1 2 3 4 17 1 2 3 4 17 BCLK RDEDGE = HI SOUT OUTPUT LEFT DATA MSB MSB-1 MSB-2 ZEROS RIGHT DATA MSB MSB-1 MSB-2 ZEROS LSB ZEROS LSB WCLK INPUT RIGHT TAG LEFT TAG TAG OUTPUT MSB MSB 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 31 18 32 1 2 3 4 16 17 18 BCLK RDEDGE = HI SOUT OUTPUT RIGHT DATA LEFT DATA ZEROS ZEROS LSB MSB MSB LSB ZEROS MSB-1 MSB-2 MSB-1 MSB-2 WCLK OUTPUT TAG OUTPUT LEFT TAG MSB RIGHT TAG MSB LSB LSB 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 INPUT BCLK RDEDGE = HI 1 2 3 4 5 17 31 32 1 2 LEFT DATA SOUT OUTPUT ZEROS 3 4 5 17 RIGHT DATA ZEROS LSB MSB MSB ZEROS LSB MSB-1 MSB-2 MSB-1 MSB-2 WCLK OUTPUT LEFT TAG TAG OUTPUT MSB RIGHT TAG LSB MSB LSB Figure 10. Serial Data Output Timing: Slave Mode, I2S-Justified, S/M = Hl, RLJUST = LO, MSBDLY = LO LRCK OUTPUT BCLK RDEDGE = LO 31 OUTPUT 32 1 2 15 16 17 18 19 32 1 2 15 16 17 18 19 32 1 2 BCLK RDEDGE = HI LEFT DATA PREVIOUS DATA SOUT OUTPUT MSB-14 LSB ZEROS RIGHT DATA MSB LSB ZEROS MSB MSB-1 MSB-2 LSB ZEROS MSB-1 MSB-2 WCLK OUTPUT LEFT TAG MSB LSB TAG OUTPUT RIGHT TAG MSB LSB LEFT TAG MSB LSB 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 LSB SOUT OUTPUT MSB-14 LEFT DATA ZEROS RIGHT DATA LSB MSB ZEROS MSB-1 MSB-2 LSB MSB MSB-1 MSB-2 WCLK OUTPUT TAG OUTPUT LEFT TAG MSB LSB RIGHT TAG MSB LSB 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 REV. A –15– ZEROS AD1870 LRCK OUTPUT BCLK RDEDGE = LO OUTPUT 31 32 1 2 3 16 17 31 18 32 1 2 3 16 17 18 BCLK RDEDGE = HI SOUT OUTPUT LEFT DATA ZEROS RIGHT DATA MSB ZEROS LSB MSB ZEROS LSB MSB-1 MSB-2 MSB-1 MSB-2 WCLK OUTPUT RIGHT TAG LEFT TAG TAG OUTPUT MSB LSB MSB LSB 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 OUTPUT 32 1 2 3 4 17 31 32 1 2 3 4 17 BCLK RDEDGE = HI SOUT OUTPUT LEFT DATA ZEROS MSB RIGHT DATA MSB MSB-1 MSB-2 ZEROS LSB MSB-1 MSB-2 ZEROS LSB WCLK OUTPUT LEFT TAG MSB LSB TAG OUTPUT RIGHT TAG LSB MSB Figure 14. Serial Data Output Timing: Master Mode, I2S-Justified, S/M = LO, RLJUST = LO, MSBDLY = LO LRCK INPUT BCLK RDEDGE = LO INPUT 31 32 1 2 3 4 5 16 17 18 19 20 21 32 1 2 BCLK RDEDGE = HI SOUT OUTPUT PREVIOUS DATA LSB MSB MSB-14 LEFT DATA WCLK OUTPUT TAG OUTPUT RIGHT DATA LSB MSB-1 MSB-2 MSB-3 MSB-4 MSB-1 MSB-2 MSB-3 MSB-4 HI LEFT TAG LSB MSB LSB MSB LEFT DATA MSB MSB-1 HI RIGHT TAG LSB MSB LEFT TAG 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 INPUT 1 2 3 4 5 6 17 18 19 20 21 22 1 2 3 BCLK RDEDGE = HI PREVIOUS DATA LEFT DATA LSB MSB MSB-14 MSB-1 MSB-2 MSB-3 MSB-4 SOUT OUTPUT WCLK OUTPUT RIGHT DATA LSB MSB MSB-1 MSB-2 MSB-3 MSB-4 HI LEFT TAG TAG OUTPUT MSB HI LEFT TAG RIGHT TAG LSB MSB LEFT DATA MSB MSB-1 LSB LSB MSB RIGHT TAG LSB Figure 16. Serial Data Output Timing: Slave Mode, I 2S-Justified, 32-Bit Frame Mode, S/M = Hl, RLJUST = LO, MSBDLY = LO CLKIN INPUT tDLYCKB BCLK OUTPUT (64 x fS) tBPWL RDEDGE = LO BCLK OUTPUT (64 x fS) XMIT XMIT XMIT XMIT tBPWH RDEDGE = HI tBPWH LRCK OUTPUT WCLK OUTPUT tDLYBWR tDLYBWF tDLYBLR tDLYDT DATA AND TAG OUTPUTS Figure 17. Master Mode Clock Timing tBPWL BCLK INPUT RDEDGE = LO BCLK OUTPUT RDEDGE = HI XMIT SAMPLE XMIT SAMPLE 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 REV. A tBPWH –17– tBPWL MSB 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 14 1 0.3937 (10.00) 0.1043 (2.65) 0.7125 (18.10) 0.0926 (2.35) 0.6969 (17.70) 0.0291 (0.74) 0.0098 (0.25) 0.0118 (0.30) 0.0040 (0.10) 0.0500 (1.27) BSC x 45° 8ⴗ 0.0500 (1.27) 0.0192 (0.49) 0.0125 (0.32) 0ⴗ 0.0157 (0.40) 0.0138 (0.35) 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– PRINTED IN U.S.A. C00944–0–6/02(A)