Analog Devices Inc. AD1870AR-REEL

Overview

AD1870AR-REEL from Analog Devices is a stereo, 16-bit sigma-delta analog-to-digital converter (ADC) designed for digital audio bandwidth applications. It operates from a single 5 V supply, features fourth-order noise-shaping modulators per channel, three-stage linear-phase FIR decimation filters, and delivers 92 dB typical dynamic range with A-weighting. It supports 44.1 kHz and 48 kHz sampling rates in consumer audio receivers and portable recorders.

For engineers reviewing the AD1870AR-REEL datasheet, AD1870AR-REEL pinout, AD1870AR-REEL application, or AD1870AR-REEL equivalent, key selection considerations include its single-supply operation, on-chip voltage reference (2.25 V nominal), 256×/384× f_S clock flexibility, I²S-compatible serial output formatting, and integrated single-ended-to-differential input conversion.

Technical Context

The AD1870AR-REEL implements a proprietary fourth-order, single-bit feedforward-feedback sigma-delta modulator architecture per channel, with internal differential signal paths and autocalibration for dc offset correction. Its decimation filters operate at 64 × f_S, reducing bitstream data to 16-bit stereo words at f_S with 0.006 dB pass-band ripple and >90 dB stop-band attenuation.

Digital interface timing is configurable via pin-strapped modes: Master/Slave select (S/M), left/right justify (RLJUST), MSB delay (MSBDLY), and clock ratio (384/256). The TAG output provides real-time overrange status (2-bit TTL-level indication), while RDEDGE controls BCLK edge polarity for serial data capture.

Key Specifications

Pinout & Package

AD1870AR-REEL is housed in a 28-lead plastic SOIC package (R-28), with physically separated analog and digital supply/ground pins to minimize coupling. Pin 1 is LRCK (left/right clock); pin 28 is CLKIN (master clock input). All analog inputs (VINL/VINR) and reference outputs (VREFL/VREFR) are on the left/right halves of the package to support symmetrical layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stereo sigma-delta ADC applications.

Compared with AK5355VT and CS5330-CQZ, the AD1870AR-REEL uniquely integrates autocalibration, on-chip 2.25 V reference, TAG overrange flag, and pin-configurable serial formats - reducing component count and firmware complexity in 5 V consumer audio systems.

Availability

AD1870AR-REEL is available at Aetrix Electronics and suitable for consumer digital audio receivers, portable digital recorders, and multimedia sound cards requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for AD1870AR-REEL includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD1870AR-REEL belongs to Analog Devices' precision audio ADC product line, engineered specifically for single-supply, low-power, high-fidelity digitization in consumer electronics - emphasizing integration, ease of use, and robustness against power supply noise and thermal drift.

FAQ

What is the primary function of the AD1870AR-REEL in an audio system?

The AD1870AR-REEL serves as a stereo, 16-bit sigma-delta analog-to-digital converter that digitizes two single-ended analog audio channels into time-multiplexed serial digital output. It performs oversampling, noise shaping, and digital decimation internally, delivering high-fidelity audio data with 92 dB typical A-weighted dynamic range. Its integrated features - including autocalibration, on-chip voltage reference, and flexible serial interface - make the AD1870AR-REEL ideal for consumer audio receivers and portable recorders where board space and power efficiency are critical.

Does the AD1870AR-REEL require external analog antialias filtering?

The AD1870AR-REEL requires only passive RC antialias filtering: four external 470 pF NPO ceramic capacitors (two per channel) placed at CAPL1/CAPL2 and CAPR1/CAPR2 pins. No active components or op-amps are needed because its internal single-ended-to-differential converters and fourth-order modulator relax antialias requirements. A simple single-pole RC filter with a 240 kHz cutoff - implemented using the recommended 300 Ω resistor and 2.2 nF capacitor - provides adequate suppression of out-of-band energy without degrading audio band linearity.

How does the TAG output on the AD1870AR-REEL improve system-level audio monitoring?

The TAG output on the AD1870AR-REEL provides real-time, sample-synchronous overrange status using two TTL-compatible bits (MSB/LSB) that indicate whether the current input sample is more than 1 dB under full scale, within 1 dB under, within 1 dB over, or more than 1 dB over full scale. Unlike peak-hold indicators, TAG updates every sample - enabling host processors to dynamically adjust gain or trigger clipping warnings without post-processing. This feature is especially valuable in AD1870AR-REEL-based recorders and mixers where maintaining headroom integrity is essential.

Can the AD1870AR-REEL operate with a 3.3 V supply?

No, the AD1870AR-REEL is specified exclusively for single 5 V ±5% operation: AVDD, DVDD1, and DVDD2 must all be 4.75–5.25 V. Its internal reference (2.25 V nominal), modulator headroom, and digital I/O thresholds (VIH = 2.4 V, VIL = 0.8 V) are optimized for 5 V logic compatibility. Attempting to run the AD1870AR-REEL at 3.3 V will result in undefined behavior, failed autocalibration, and potential damage due to violation of absolute maximum ratings. For 3.3 V systems, consider alternative sigma-delta ADCs such as the AD1974 or AK5385.

What is the group delay of the AD1870AR-REEL at 44.1 kHz sampling rate?

The AD1870AR-REEL exhibits a fixed group delay of 36/f_S seconds, resulting in 816 µs at 44.1 kHz. This delay arises entirely from the symmetric finite impulse response (FIR) decimation filter and is constant across the audio pass band due to linear phase response. Because the delay is deterministic and identical for both left and right channels, it introduces no interchannel skew - preserving stereo imaging integrity. System designers can compensate for this latency in DSP firmware or buffer management, knowing it remains stable across temperature and supply variations.