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Analog Devices Inc. AD7856AR-REEL
- Part No.:
- AD7856AR-REEL
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AD7856AR-REEL.pdf
- Description:
- IC ADC 14BIT SAR 24SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,157
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Product details
Overview
AD7856AR-REEL from Analog Devices is a 14-bit, 285 kSPS successive approximation register (SAR) analog-to-digital converter with integrated track-and-hold, 8-channel multiplexer, and on-chip reference buffer. It operates from a single 5 V supply, supports eight single-ended or four pseudo-differential inputs, and delivers ±2 LSB integral nonlinearity at 25°C with self-calibration on power-up. It is used in portable instrumentation requiring high accuracy, low power, and flexible serial interface compatibility with SPI/QSPI/8051 microcontrollers.
For engineers reviewing the AD7856AR-REEL datasheet, AD7856AR-REEL pinout, AD7856AR-REEL application, or AD7856AR-REEL equivalent, this page provides verified technical context, real-world design meaning of key specs, validated package and pin functions, confirmed alternative options, and supply-chain support details specific to the AD7856AR-REEL SOIC-24 variant.
Technical Context
The AD7856AR-REEL implements a charge redistribution SAR architecture with a 500 ns track-and-hold acquisition time and internal 4.096 V reference buffered via REFIN/REFOUT. Its control logic supports software-initiated conversion via the CONVST bit in the 14-bit write-only control register and enables system-level calibration through dedicated CALSLT and CALMD bits.
It features dual power management modes controlled by PMGT1/PMGT0 bits and SLEEP pin: full power-down (2.5 mW typ) and partial power-down (5.1 mW typ), both retaining calibration data. Serial communication uses a configurable 3-wire SPI-compatible interface (Mode 2 default) with SYNC framing, supporting DIN/DOUT bidirectional operation in Mode 1.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 14-bit - guarantees monotonic output with no missing codes up to 13 bits; enables 16,384 distinct digital levels for precision measurement. |
| Throughput Rate | 285 kSPS - achieves full 14-bit conversion every 3.5 µs (A-grade), supporting real-time sampling of signals up to 10 MHz full-power bandwidth. |
| INL / DNL | ±2 LSB max - ensures end-point linearity error ≤ ±0.012% of full scale; sufficient for 12-bit effective resolution in closed-loop control. |
| Power Dissipation | 60 mW typ (normal), 2.5 mW typ (auto power-down) - reduces thermal load in battery-powered PDAs and medical handhelds without sacrificing speed. |
| Reference Range | 1.2 V to VDD - allows direct use of external references (e.g., 2.5 V or 4.096 V) or AVDD as reference source, simplifying BOM in single-supply systems. |
| Input Configuration | 8 single-ended or 4 pseudo-differential channels - enables simultaneous monitoring of multiple sensors (e.g., thermocouples + RTDs) with shared negative input. |
| SNR @ 10 kHz | 78 dB min - corresponds to ~12.7 effective bits; adequate for high-fidelity data acquisition in industrial sensor interfaces. |
Pinout & Package
AD7856AR-REEL is housed in a 24-lead small outline integrated circuit (SOIC) package, 0.3 inch wide, RoHS-compliant, with standard JEDEC MS-013AC footprint and 1.27 mm pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 CONVST | Convert Start Input | Edge-triggered command to latch analog input and begin conversion; tied high if unused to avoid spurious triggers. |
| 2 BUSY | Conversion Status Output | Active-high open-drain signal indicating active conversion or calibration; used for hardware handshaking with µC. |
| 3 SLEEP | Power Management Control | Logic-low entry into low-power mode; retains calibration memory and reference bias during sleep, enabling fast wake-up. |
| 4 REFIN/REFOUT | Reference I/O Node | Provides 4.096 V internal reference or accepts external reference; requires CREF1 (0.1 µF) and CREF2 (0.01 µF) decoupling to AGND. |
| 5 AVDD, 6 AGND | Analog Supply & Ground | Separate analog domain for precision conversion; must be decoupled independently from digital supply to minimize noise coupling. |
| 9–16 AIN1–AIN8 | Configurable Analog Inputs | Selectable via control register as eight single-ended (vs. AGND) or four pseudo-differential pairs; AIN(+) must never fall below AIN(–). |
| 17 CAL | Calibration Trigger | Falling edge resets calibration logic; rising edge initiates self- or system calibration; 10 nF cap to DGND enables auto-cal on power-up. |
| 18 DVDD, 19 DGND | Digital Supply & Ground | Isolated digital domain powers serial interface and control logic; must share common ground with AGND at single point. |
| 20 DOUT, 21 DIN | Serial Data I/O | 16-bit serial word interface; DIN functions as input only in Mode 2 (default), but bidirectional in Mode 1 for two-wire operation. |
| 22 CLKIN | Master Clock Input | Accepts 6 MHz (A-grade) or 4 MHz (K-grade) clock; determines conversion time (21 cycles) and calibration duration. |
| 23 SCLK, 24 SYNC | Serial Interface Timing | SCLK clocks data transfer; SYNC frames each 16-bit transaction-low-active pulse synchronizes read/write boundaries. |
Key Features
| Feature | Design Value |
|---|---|
| Single 5 V supply operation | Eliminates need for dual ±5 V or ±15 V rails, reducing board area and cost in portable medical and test equipment. |
| Self- and system calibration | On-chip offset/gain correction compensates for drift over temperature (–40°C to +105°C) and aging, extending recalibration intervals. |
| Flexible serial interface | Hardware- and software-compatible with SPI, QSPI, and 8051 protocols-enables reuse of existing firmware drivers across platforms. |
| Automatic power-down after conversion | Reduces average current to 2.5 mW typ without external control, critical for multi-channel battery-powered data loggers. |
| Pseudo-differential input architecture | Rejects common-mode noise on shared return paths (e.g., sensor cables), improving SNR in noisy industrial environments. |
Applications
| Portable Medical Instrumentation | Battery-Powered Data Acquisition |
|---|---|
|
Use Scenario: Handheld ECG monitor acquiring lead I, II, III, and respiratory impedance simultaneously. IC Role / Device Role / Timing Role: 14-bit ADC digitizing conditioned analog biosignals at ≥250 SPS per channel with <10 µV offset drift. Use Value: Eight single-ended inputs allow concurrent sampling of four differential leads plus auxiliary sensors without external MUX. |
Use Scenario: Wireless environmental sensor node measuring temperature, humidity, and CO₂ over 24-hour duty cycle. IC Role / Device Role / Timing Role: Low-power SAR ADC performing burst-mode conversions triggered by µC, then entering auto power-down. Use Value: 2.5 mW auto power-down mode extends AA battery life beyond 12 months while maintaining 14-bit resolution. |
| Industrial Process Monitoring | High-Speed Modem Analog Front End |
|
Use Scenario: PLC analog input module conditioning 4–20 mA current loops from pressure, flow, and level transmitters. IC Role / Device Role / Timing Role: Pseudo-differential ADC rejecting ground loop noise between field devices and controller backplane. Use Value: –90 dB channel-to-channel isolation prevents crosstalk when scanning multiple 4–20 mA channels on shared PCB. |
Use Scenario: V.34 modem analog front end digitizing baseband receive signals before DSP demodulation. IC Role / Device Role / Timing Role: High-speed 285 kSPS ADC capturing full-spectrum analog waveforms up to 10 MHz bandwidth. Use Value: 78 dB SNR at 10 kHz supports >12-bit ENOB for accurate constellation mapping in QAM-128 modulation schemes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 14-bit SAR ADC applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD7856KR-REEL | K-grade (0°C to +105°C) vs. A-grade (–40°C to +105°C); same SOIC-24 package and pinout; lower max clock (4 MHz) limits throughput to 102 kSPS. | Suitable for commercial-temperature industrial controllers where extended cold-start operation is not required. | Select AD7856KR-REEL only if ambient operating range excludes sub-zero conditions and lower sample rate is acceptable. |
| AD7682BCPZ-RL7 | 16-bit, 250 kSPS, SPI-only interface, no internal reference; requires external 4.096 V ref; consumes 6.5 mW in normal mode. | Better resolution for precision metrology, but lacks built-in reference and pseudo-differential flexibility of AD7856AR-REEL. | Choose AD7682BCPZ-RL7 when 16-bit accuracy is mandatory and external reference sourcing is feasible; avoid if system-level calibration or 8-channel flexibility is needed. |
Compared with AD7856KR-REEL, the AD7856AR-REEL supports wider temperature range and higher throughput; compared with AD7682BCPZ-RL7, it trades 2-bit resolution for integrated reference, self-calibration, and channel configuration-making it more suitable for compact, self-contained sensor nodes.
Availability
AD7856AR-REEL is available at Aetrix Electronics and suitable for portable medical instrumentation, battery-powered data loggers, and industrial process monitoring requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for AD7856AR-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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.
The AD7856AR-REEL belongs to Analog Devices' precision SAR ADC product line, designed specifically for portable, low-power, multi-channel data acquisition systems requiring on-chip calibration and flexible serial interfacing in space-constrained designs.
FAQ
What is the maximum sample rate of the AD7856AR-REEL and under what conditions?
The AD7856AR-REEL achieves a maximum throughput rate of 285 kSPS when operated in A-grade configuration with a 6 MHz master clock (CLKIN). This requires using Interface Mode 2 with read/write operations performed during conversion, and allowing ≥330 ns acquisition time between BUSY falling edge and next CONVST rising edge. The K-grade version (e.g., AD7856KR-REEL) is limited to 102 kSPS at 4 MHz CLKIN.
Does the AD7856AR-REEL require external reference components, and if so, which ones?
Yes, the AD7856AR-REEL requires two external capacitors on the reference pins: a 0.1 µF multilayer ceramic capacitor (CREF1) and a 470 nF NPO-type capacitor (CREF2), both connected between their respective pins (CREF1, CREF2) and AGND. These stabilize the internal 4.096 V reference and support DAC charge redistribution during conversion. No external voltage reference IC is required unless overriding the internal reference.
How does the AD7856AR-REEL handle channel selection and input configuration?
The AD7856AR-REEL uses the SGL/DIFF bit and CH2–CH0 bits in its 14-bit control register to configure inputs: SGL/DIFF = 1 selects eight single-ended channels referenced to AGND; SGL/DIFF = 0 selects four pseudo-differential pairs (e.g., AIN1–AIN2). Channel selection is software-controlled-no hardware jumpers or external logic are needed-enabling dynamic reconfiguration during runtime.
Can the AD7856AR-REEL perform system-level calibration, and how is it initiated?
Yes, the AD7856AR-REEL supports both self-calibration and system calibration. System calibration is initiated by setting CALMD = 1 and STCAL = 1 in the control register, then asserting the CAL pin. It corrects for external gain/offset errors using user-applied reference voltages within ±0.0375 × VREF (offset) and ±0.01875 × VREF (gain) spans, as defined in the calibration section of the datasheet.
What power management modes does the AD7856AR-REEL support, and how are they controlled?
The AD7856AR-REEL supports three power states: normal (60 mW typ), full power-down (2.5 mW typ), and partial power-down (5.1 mW typ). These are controlled jointly by the SLEEP pin (logic low enables power-down) and PMGT1/PMGT0 bits in the control register. Full power-down disables the internal reference; partial power-down retains reference bias for faster wake-up, both preserving calibration coefficients in memory.
AD7856AR-REEL Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Number of Bits:
- 14
- Sampling Rate (Per Second):
- 285k
- Number of Inputs:
- 4, 8
- Input Type:
- Pseudo-Differential, Single Ended
- Data Interface:
- SPI
- Configuration:
- MUX-S/H-ADC
- Ratio - S/H:ADC:
- 1:1
- Number of A/D Converters:
- 1
- Architecture:
- SAR
- Reference Type:
- External, Internal
- Voltage - Supply, Analog:
- 5V
- Voltage - Supply, Digital:
- 5V
- Features:
- -
- Operating Temperature:
- -40°C ~ 105°C
- Supplier Device Package:
- 24-SOIC
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD7856AR-REEL FAQ
1.How can I place an order for AD7856AR-REEL through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7856AR-REEL 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 AD7856AR-REEL reliable?
The price and inventory of AD7856AR-REEL are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7856AR-REEL is usually 5 days.
3.What payment methods are accepted for AD7856AR-REEL?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7856AR-REEL transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7856AR-REEL?
AD7856AR-REEL orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7856AR-REEL 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 AD7856AR-REEL?
For technical support, including AD7856AR-REEL datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7856AR-REEL requirements.
6.How does Aetrix verify that AD7856AR-REEL is sourced from the original manufacturer or authorized distributors?
All AD7856AR-REEL 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 AD7856AR-REEL meets industry standards.
7.What is the process for return or replacement of AD7856AR-REEL?
All AD7856AR-REEL units undergo pre-shipment inspection (PSI). If there is an issue with AD7856AR-REEL, 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 AD7856AR-REEL part is unused and in its original packaging.
Return procedure for AD7856AR-REEL:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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