Analog Devices Inc. AD1556ASRL

Overview

AD1556ASRL from Analog Devices is a 24-bit sigma-delta digital filter/decimator IC designed to process bitstream output from the AD1555 modulator. It implements a programmable FIR filter with output word rates from 250 SPS to 16 kSPS, delivers ±0.05 dB pass-band ripple, –135 dB stop-band attenuation (except at 16 kHz), and operates on a single 2.85–5.25 V digital supply. It enables high-precision low-frequency data acquisition in seismic instrumentation.

For engineers reviewing the AD1556ASRL datasheet, AD1556ASRL pinout, AD1556ASRL application, or AD1556ASRL equivalent, key selection criteria include its decimation rate configurability (BW0–BW2), hardware/software mode control (H/S), error flag signaling (ERROR), serial interface timing (SCLK/DIN/DOUT), and compatibility with AD1555-based front-end architectures.

Technical Context

The AD1556ASRL implements a fixed-coefficient FIR digital filter with programmable decimation ratios, supporting eight output word rates (250 Hz to 16 kHz) defined by BW0–BW2 inputs or configuration register writes. Its filter response includes group delay ranging from 0.984 ms (16 kHz) to 93 ms (250 Hz), and it accepts either MDATA (from AD1555) or TDATA as input via CSEL.

It features dual-mode operation: hardware mode (H/S = high) uses CB0–CB4 and BW0–BW2 pins for static configuration, while software mode (H/S = low) allows dynamic register updates via serial interface. The ERROR pin signals modulator or filter errors, and RESET clears status and reloads hardware defaults.

Key Specifications

Pinout & Package

AD1556ASRL is housed in a 44-lead MQFP (S-44A) package with exposed thermal pad, rated for –55°C to +85°C operation. Pin functions are electrically validated per Analog Devices' AD1555/AD1556 Rev. B datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital filter/decimator applications.

Compared with AD7714BRU and ADS1258IPWR, AD1556ASRL uniquely pairs with the AD1555 modulator to deliver optimized low-noise performance at variable output rates up to 16 kSPS, while maintaining strict separation of analog and digital signal paths for EMI resilience.

Availability

AD1556ASRL is available at Aetrix Electronics and suitable for seismic instrumentation, chromatography analyzers, and automated test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD1556ASRL 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 AD1556ASRL belongs to Analog Devices' precision sigma-delta converter chipset family, engineered specifically for ultra-low-noise, high-dynamic-range measurement of low-frequency analog signals in demanding scientific and industrial applications.

FAQ

What is the function of the H/S pin on the AD1556ASRL?

The H/S (Hardware/Software) pin on the AD1556ASRL determines the configuration method: when high, the device uses pin-strapped settings (BW0–BW2, CB0–CB4) for fixed operation; when low, it accepts SPI register writes for dynamic reconfiguration. This dual-mode capability allows AD1556ASRL to support both factory-set instruments and field-upgradable systems without hardware modification.

Does the AD1556ASRL require an external clock source, and what is its nominal frequency?

Yes, the AD1556ASRL requires an external CLKIN signal with a nominal frequency of 1.024 MHz, as specified in the AD1555/AD1556 Rev. B datasheet. This clock is internally divided by four to generate the MCLK signal for the AD1555 modulator. Deviations beyond ±5% (0.975–1.075 MHz) may affect decimation accuracy and dynamic performance of the AD1556ASRL.

How does the ERROR pin on the AD1556ASRL behave during normal and fault conditions?

The ERROR pin on the AD1556ASRL is an open-drain, active-low output. During normal operation, it remains high (pulled up internally ~100 kΩ). When a modulator overrange condition (detected via MFLG) or digital filter error occurs, ERROR goes low and the corresponding bit in the status register is set. This behavior is documented in the AD1555/AD1556 Rev. B datasheet, page 11.

Can the AD1556ASRL operate with a 3.3 V digital supply, and what is its power dissipation at that voltage?

Yes, the AD1556ASRL is fully specified for VL = 2.85 V to 5.25 V, including standard 3.3 V logic supplies. At VL = 3.3 V and output word rate FO = 1 kHz, its typical power dissipation is 6.2 mW, with quiescent current of 4–5 mA. This low power enables use in portable or energy-constrained systems where the AD1556ASRL must coexist with battery-operated AD1555 front-ends.

What is the purpose of the CSEL pin on the AD1556ASRL, and how does it affect data flow?

The CSEL (Filter Input Select) pin on the AD1556ASRL routes the digital filter input: when low, MDATA (bitstream from AD1555) is selected; when high, TDATA (user-provided test data) is used instead. This enables in-system validation of the AD1556ASRL's filter response without disconnecting the modulator, supporting diagnostic routines and calibration verification per the AD1555/AD1556 Rev. B functional description.