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Analog Devices Inc. AD1556AS
- Part No.:
- AD1556AS
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 44-QFP
- Datasheet:
-
AD1556AS.pdf
- Description:
- IC ADC PGA 24BIT LN 44-MQFP
- Quantity:
- Payment:
- Shipping:
Inventory:15,415
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Product details
Overview
AD1556AS from Analog Devices is a 24-bit sigma-delta digital filter/decimator IC designed to process bitstream output from the AD1555 modulator, delivering high-precision ADC functionality with programmable output word rates from 250 SPS to 16 kSPS, ±0.05 dB pass-band ripple, –135 dB stop-band attenuation (except at 16 kHz), and 6.2 mW typical power dissipation at 3.3 V. It serves as the digital backend in high-dynamic-range measurement systems.
For engineers reviewing the AD1556AS datasheet, AD1556AS pinout, AD1556AS application, or AD1556AS equivalent, this page provides verified technical context, validated pin functions, confirmed filter performance specs across all output rates, real-world seismic and chromatography use cases, and two manufacturer-validated alternative parts with documented functional trade-offs.
Technical Context
The AD1556AS implements a fixed-coefficient FIR digital filter with decimation, accepting a 1.024 MHz CLKIN and generating MCLK for the AD1555 at 256 kHz. Its hardware/software mode control (H/S pin) enables configuration via parallel CB0–CB4 inputs or serial register writes, supporting both standalone and synchronized multi-device operation via SYNC and wired-OR ERROR/DRDY outputs.
Filter characteristics are fully defined per output word rate (FO): group delay ranges from 0.984 ms at 16 kHz to 93 ms at 250 Hz; –3 dB bandwidth scales linearly from 6000 Hz down to 93.75 Hz; and stop-band edge shifts from 8000 Hz to 125 Hz - all confirmed in Table II of the datasheet for the AD1556AS grade.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Word Rate | 250 SPS to 16 kSPS - defines system sampling resolution and anti-aliasing cutoff; selectable via BW0–BW2 pins or register |
| Pass-Band Ripple | ±0.05 dB - ensures amplitude fidelity within signal band without post-processing correction |
| Stop-Band Attenuation | –135 dB (all FO except 16 kHz); –86 dB at FO = 16 kHz - guarantees rejection of out-of-band quantization noise |
| Power Dissipation | 6.2 mW typical at VL = 3.3 V, FO = 1 kHz - enables low-power remote data acquisition |
| Supply Voltage Range | VL = 2.85 V to 5.25 V - supports both 3.3 V and 5 V logic domains without level-shifting |
| Operating Temperature | –55°C to +85°C - qualified for extended industrial and aerospace environments |
| Quiescent Current | 4 mA to 5 mA at VL - enables accurate power budgeting in battery-backed systems |
Pinout & Package
AD1556AS is housed in a 44-lead MQFP package (S-44A), with exposed thermal pad, lead pitch 0.8 mm, and body size 10 mm × 10 mm. Pin 1 identifier located at top-left corner; pins 1, 21, 27, 28, and 33 are NC (no connect). DGND pins (12, 23, 24, 34) must be tied to common digital ground plane; VL pins (11, 22, 44) require local 0.1 µF + 10 µF decoupling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CLKIN | Master clock input | Accepts 0.975–1.075 MHz TTL/CMOS clock; internally divided by 4 to drive AD1555 MCLK |
| SYNC | Synchronization trigger | Resets filter convolution on first CLKIN rising edge; enables deterministic start-up and multi-device alignment |
| MDATA | Modulator bitstream input | Receives return-to-zero ones-density stream from AD1555; timing-critical interface requiring <30 ns setup |
| DOUT / DRDY / CS / R/W / SCLK / RSEL / DIN | Serial interface signals | Supports 24-bit read/write access to conversion data and status register; DRDY active-high indicates valid data |
| ERROR | Open-drain error flag | Asserts low on modulator overrange or filter error; internal 100 kΩ pull-up enables wired-OR with other AD1556AS units |
| PWRDN | Hardware power-down control | Stops convolution cycles and MCLK generation while preserving register state; exits only after SYNC assertion |
| H/S | Mode select | High = hardware mode (pins set configuration); Low = software mode (register-controlled) |
| BW0–BW2 | Decimation rate select | Directly configure FO from 250 SPS to 16 kSPS; values latched on RESET or H/S high transition |
Key Features
| Feature | Design Value |
|---|---|
| FIR digital filtering with programmable decimation | Enables precise, jitter-immune conversion without external analog filters; eliminates antialiasing design complexity |
| Wired-OR compatible ERROR and DRDY outputs | Allows daisy-chaining multiple AD1556AS devices on shared bus without external logic or arbitration |
| Hardware/software dual-mode configuration | Supports both pin-strapped field deployment and dynamic reconfiguration via serial interface |
| Low-power standby and power-down modes | Reduces current to 70 µW in PWRDN mode - critical for battery-powered seismic sensor nodes |
| Factory-trimmed pass-band ripple and group delay | Guarantees ±0.05 dB flatness and predictable latency across temperature and supply voltage |
Applications
| Seismic Data Acquisition | Chromatography Systems |
|---|---|
Use Scenario: High-resolution digitization of low-frequency (<100 Hz), microvolt-level ground motion signals from geophone arrays deployed in remote locations. IC Role / Device Role / Timing Role: Digital decimator and filter backend for AD1555 modulator; converts bitstream into calibrated 24-bit words at 250–1000 SPS with ultra-low noise floor. Use Value: Achieves >125 dB dynamic range at 4 ms integration time, enabling detection of weak seismic events buried in thermal noise. |
Use Scenario: Precision measurement of eluent concentration peaks in gas/liquid chromatographs, where signal slew rates are slow (<10 Hz) but amplitude resolution must exceed 1 ppm. IC Role / Device Role / Timing Role: Final-stage digital filter in a modular ADC subsystem; accepts modulator output and delivers stable, low-drift 24-bit results synchronized to detector sampling. Use Value: ±0.05 dB pass-band ripple preserves peak shape integrity; –135 dB stop-band attenuation prevents harmonic distortion from corrupting trace-level analyte quantification. |
| Automatic Test Equipment (ATE) | High-Accuracy Sensor Signal Conditioning |
Use Scenario: Calibration-grade DC and low-frequency AC measurements in benchtop ATE platforms requiring traceable accuracy and repeatability over temperature. IC Role / Device Role / Timing Role: Programmable-rate digital filter core in a dual-channel 24-bit ADC module; configured via serial interface for flexible test sequence timing. Use Value: Hardware mode (H/S = high) allows fixed-rate operation during production testing; software mode enables dynamic FO changes between test steps without FPGA intervention. |
Use Scenario: Signal conditioning for strain gauges, RTDs, and thermopiles in industrial process controllers where long-term offset drift and gain stability are critical. IC Role / Device Role / Timing Role: Decimation engine paired with AD1555's PGA to resolve sub-microvolt signals; leverages 93 ms group delay at 250 Hz for optimal noise averaging. Use Value: 70 µW power-down mode extends battery life in wireless sensor transmitters; –55°C to +85°C rating ensures reliability in harsh plant-floor environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar digital filter/decimator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD1556AP | Same architecture and pinout; rated for 0°C to +85°C only (not extended temp) | Not suitable for aerospace, downhole, or outdoor unheated enclosures | Select AD1556AP only for commercial-grade instrumentation with controlled ambient |
| AD7714BRU | Integrated sigma-delta ADC (modulator + filter in one chip); 24-bit, SPI interface; no external modulator required | Reduces BOM count but lacks AD1556AS's independent modulator clocking and SYNC-synchronized multi-unit operation | Choose AD7714BRU when system-level integration outweighs need for distributed modulator/filter architecture |
Compared with AD1556AP, the AD1556AS offers guaranteed operation down to –55°C and is the only variant qualified for military/aerospace use; compared with AD7714BRU, it enables higher system-level flexibility through separate modulator control, precise inter-device synchronization, and lower total noise in cascaded configurations.
Availability
AD1556AS is available at Aetrix Electronics and suitable for seismic monitoring, chromatography instrumentation, and automatic test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for AD1556AS 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, founded in 1965 and headquartered in Wilmington, MA.
The AD1556AS belongs to Analog Devices' precision sigma-delta converter chipset family, engineered specifically for ultra-low-noise, high-dynamic-range measurement applications in geophysical, analytical, and industrial instrumentation.
FAQ
What is the primary function of the AD1556AS in a signal chain?
The AD1556AS functions exclusively as a digital FIR filter and decimator, converting the 1-bit, high-speed bitstream from the AD1555 sigma-delta modulator into a calibrated 24-bit parallel or serial output word. It does not perform analog signal conditioning or modulation - its role begins only after the AD1555 generates the bitstream, and it is not usable without that companion device. The AD1556AS itself contains no analog circuitry.
Can the AD1556AS operate independently of the AD1555?
No - the AD1556AS requires a compatible sigma-delta bitstream input, and its MDATA pin is specifically designed to accept the return-to-zero format generated by the AD1555. While TDATA can be used for test patterns, the AD1556AS lacks internal modulator circuitry and cannot digitize analog signals directly. Using it without the AD1555 or an equivalent modulator yields no valid conversion result.
How does the H/S pin affect configuration of the AD1556AS?
When H/S is high, the AD1556AS operates in hardware mode: BW0–BW2 and CSEL pin states are latched at RESET to set output word rate and filter input source. When H/S is low, configuration is controlled entirely by serial writes to the Configuration Register via DIN/SCLK, enabling runtime reprogramming. Both modes retain full access to the Status Register and conversion data.
What is the significance of the 70 µW power-down current specification for the AD1556AS?
The 70 µW power-down current (measured at VL = 3.3 V) reflects complete suspension of FIR convolution and internal clocking while preserving register contents and serial interface readiness. This enables rapid wake-up (<100 µs after SYNC) without reinitialization - essential for duty-cycled sensor nodes in seismic or environmental monitoring where average power must remain below 100 µW.
Does the AD1556AS support daisy-chained serial communication with multiple devices?
Yes - the AD1556AS supports true daisy-chained read operations using the DRDY and SCLK signals. When DRDY goes high, the master controller can initiate a read cycle; DOUT of the first device drives DIN of the next, allowing sequential 24-bit reads across up to 16 devices on a single 3-wire bus (CS, SCLK, DOUT/DIN), provided each has unique RSEL and CS decoding.
AD1556AS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 44-QFP
- Packaging:
- Bag
- Product Status:
- Obsolete
- Number of Bits:
- 24
- Sampling Rate (Per Second):
- 256k
- Number of Inputs:
- -
- Input Type:
- -
- Data Interface:
- -
- Configuration:
- -
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 1
- Architecture:
- -
- Reference Type:
- -
- Voltage - Supply, Analog:
- -
- Voltage - Supply, Digital:
- -
- Features:
- -
- Operating Temperature:
- -55°C ~ 85°C
- Supplier Device Package:
- 44-MQFP (10x10)
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD1556AS FAQ
1.How can I place an order for AD1556AS through Aetrix?
Please submit a Request for Quotation (RFQ) for AD1556AS on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD1556AS reliable?
The price and inventory of AD1556AS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD1556AS is usually 5 days.
3.What payment methods are accepted for AD1556AS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD1556AS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD1556AS?
AD1556AS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD1556AS order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD1556AS?
For technical support, including AD1556AS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD1556AS requirements.
6.How does Aetrix verify that AD1556AS is sourced from the original manufacturer or authorized distributors?
All AD1556AS products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD1556AS meets industry standards.
7.What is the process for return or replacement of AD1556AS?
All AD1556AS units undergo pre-shipment inspection (PSI). If there is an issue with AD1556AS, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD1556AS part is unused and in its original packaging.
Return procedure for AD1556AS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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