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Analog Devices Inc. AD7856KR
- Part No.:
- AD7856KR
- Manufacturer:
- Analog Devices Inc.
- Category:
- Analog to Digital Converters (ADC)
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AD7856KR.pdf
- Description:
- IC ADC 14BIT 8CH 5V 24-SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:6,424
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Product details
Overview
AD7856KR from Analog Devices is a 14-bit, 285 kSPS sampling ADC operating from a single 5 V supply, featuring eight single-ended or four pseudo-differential analog inputs, on-chip reference (4.096 V), and SPI/QSPI/μP-compatible serial interface. It delivers ±2 LSB integral nonlinearity, 78 dB SNR at 10 kHz input, and supports system calibration for precision instrumentation.
For engineers reviewing the AD7856KR datasheet, AD7856KR pinout, AD7856KR application, or AD7856KR equivalent, this page provides verified technical context, real-world timing behavior, power-down modes, calibration architecture, and validated alternative options for battery-powered medical instruments, portable data acquisition, and industrial control systems.
Technical Context
The AD7856KR uses a successive approximation register (SAR) architecture with integrated track-and-hold, charge redistribution DAC, and programmable serial interface supporting Mode 1 (two-wire) and Mode 2 (three-wire) SPI-compatible protocols. Its internal calibration memory stores offset and gain coefficients across temperature.
It implements automatic power-down after conversion (2.5 mW typ), flexible reference handling (1.2 V to VDD), and dual-domain power management: AVDD/DGND separation enables noise isolation between analog and digital sections, while SLEEP pin and PMGT bits in the control register enable full or partial power-down states.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Resolution | 14-bit SAR ADC with straight binary output coding - ensures unambiguous digital representation of analog signals up to 16,384 levels. |
| Sampling Rate | 285 kSPS maximum throughput (A-grade); K-grade operates at 102 kSPS with 4 MHz master clock - defines real-time signal capture capability for transient event monitoring. |
| INL / DNL | ±2 LSB max integral and differential nonlinearity - guarantees monotonicity and no missing codes to 13 bits, critical for closed-loop control accuracy. |
| SNR @ 10 kHz | 78 dB min (typ 79.5 dB) - determines effective resolution (~13.0 ENOB) when digitizing low-noise sensor outputs. |
| Power Dissipation | 60 mW typ normal mode; 2.5 mW typ auto power-down - enables extended operation in handheld PDAs and battery-powered medical devices. |
| Analog Input Range | 0 V to VREF (up to 5 V) - allows direct interfacing with rail-to-rail op-amp outputs without level-shifting circuitry. |
| Reference Voltage | 4.096 V nominal REFOUT with 20 ppm/°C tempco - provides stable scaling for high-accuracy measurements across 0°C to +105°C ambient range. |
Pinout & Package
AD7856KR is packaged in a 24-lead SOIC (R-24) with 0.3-inch body width and standard JEDEC MS-013 footprint. Pin functions are electrically validated per Analog Devices AD7856 Rev. A datasheet.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 CONVST | Convert Start trigger | Edge-sensitive input initiating T/H hold and conversion; falling edge resets BUSY, rising edge starts conversion sequence. |
| 2 BUSY | Conversion status indicator | Active-high open-drain output signaling active conversion or calibration; used for handshaking with μP or FPGA logic. |
| 3 SLEEP | Low-power mode control | Logic-low forces full power-down including internal reference shutdown; retains calibration data in nonvolatile memory. |
| 4 REFIN/REFOUT | Reference I/O node | Provides 4.096 V internal reference or accepts external 1.2–5 V reference; requires CREF1 (0.1 µF) and CREF2 (0.01 µF) to AGND. |
| 5 AVDD / 6 AGND | Analog supply & ground | Separate 5 V ±5% analog domain supply and ground - essential for minimizing digital switching noise coupling into ADC core. |
| 9–16 AIN1–AIN8 | Configurable analog inputs | Support eight single-ended (vs. AGND) or four pseudo-differential pairs; channel selection via SGL/DIFF and CH[2:0] bits in control register. |
| 17 CAL | Calibration initiation | Falling edge resets calibration logic; rising edge triggers self- or system calibration - optional 10 nF capacitor enables autocal on power-up. |
| 18 DVDD / 19 DGND | Digital supply & ground | 5 V ±5% digital domain supply and ground - decoupling required near pins to suppress serial interface noise. |
| 20 DOUT / 21 DIN | Serial data I/O | 16-bit serial interface supporting SPI/QSPI/8051 protocols; DIN functions as bidirectional I/O in Mode 1, input-only in Mode 2. |
| 22 CLKIN | Master clock input | 4 MHz clock for K-grade operation - sets conversion time (5.25 µs max), calibration duration, and serial timing parameters. |
| 23 SCLK / 24 SYNC | Serial interface timing | SCLK clocks data transfer; SYNC frames each 16-bit word - enables synchronous read/write during or after conversion. |
Key Features
| Feature | Design Value |
|---|---|
| Self- and system calibration | On-chip calibration memory stores offset/gain coefficients; supports field recalibration against external references to maintain ±2 LSB INL over temperature. |
| Flexible serial interface | Hardware-selectable Mode 1 (DIN bidirectional) or Mode 2 (DIN input-only) - eliminates need for external direction control logic in μP designs. |
| Pseudo-differential input architecture | Eight-input multiplexer supports true differential measurement (e.g., AIN1–AIN2) with >90 dB channel-to-channel isolation - rejects common-mode noise in noisy industrial environments. |
| Automatic power-down | Configurable via PMGT[1:0] bits and SLEEP pin to achieve 5 µA sleep current with external clock off - extends battery life in portable data loggers. |
| Single-supply operation | 5 V only powers both analog and digital domains - simplifies PCB layout by eliminating dual-rail regulators and reduces BOM cost in space-constrained designs. |
Applications
| Battery-Powered Medical Instrumentation | Portable Data Acquisition Systems |
|---|---|
Use Scenario: Continuous ECG waveform digitization in handheld patient monitors with 24-hour battery life. IC Role / Device Role / Timing Role: Primary 14-bit sampling ADC acquiring 8-channel biopotential signals at 102 kSPS with on-the-fly calibration. Use Value: 60 mW typical power dissipation and automatic post-conversion power-down enable sustained operation without thermal throttling or fan cooling. |
Use Scenario: Field-deployable environmental sensor node measuring temperature, pressure, and humidity across multiple transducers. IC Role / Device Role / Timing Role: Central analog front-end ADC performing sequential channel scanning with system calibration against precision reference. Use Value: Pseudo-differential input mode rejects ground loop noise in distributed sensor wiring, while 78 dB SNR preserves dynamic range for low-level thermocouple outputs. |
| Industrial Process Control | High-Speed Modem Analog Front-End |
Use Scenario: Closed-loop PLC I/O module acquiring analog feedback from motor current sensors and position encoders. IC Role / Device Role / Timing Role: Precision ADC providing real-time feedback for PID controllers with guaranteed monotonicity (no missing codes). Use Value: ±2 LSB INL and self-calibration ensure long-term stability over 0°C to +105°C ambient, reducing need for periodic factory recalibration. |
Use Scenario: DSL or cable modem line card digitizing upstream RF signals before digital signal processing. IC Role / Device Role / Timing Role: High-speed sampling ADC capturing baseband analog signals at Nyquist rate with minimal harmonic distortion. Use Value: –86 dB THD and –90 dB IMD support clean spectral reconstruction up to 10 MHz full-power bandwidth for QAM demodulation. |
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 |
|---|---|---|---|
| AD7856AR | Same electrical specs but wider industrial temperature range (–40°C to +105°C); packaged in SOIC (R-24) identical to AD7856KR. | Required for extended-cold-environment deployments (e.g., outdoor telecom cabinets, automotive under-hood). | Select AD7856AR if operation below 0°C is needed; AD7856KR is optimized for cost-sensitive commercial-temperature applications. |
| ADS8320U | 16-bit, 100 kSPS SAR ADC with SPI interface; lower power (15 mW), no internal reference, requires external 4.096 V reference. | Higher resolution but slower sampling; lacks on-chip calibration and pseudo-differential input flexibility. | Choose ADS8320U only when 16-bit resolution outweighs need for calibration autonomy and multi-channel configurability. |
Compared with AD7856AR, AD7856KR trades extended temperature range for lower unit cost in commercial applications; compared with ADS8320U, it sacrifices 2-bit resolution to retain integrated reference, calibration, and flexible input topology - making AD7856KR optimal for compact, self-contained, medium-speed data acquisition where design simplicity and field recalibration matter.
Availability
AD7856KR is available at Aetrix Electronics and suitable for battery-powered medical instrumentation, portable data acquisition systems, and industrial process control requiring stable component supply across production lifecycles.
Supply support for AD7856KR 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 ICs, serving precision instrumentation, industrial automation, and communications markets since 1965.
The AD7856KR belongs to Analog Devices' precision SAR ADC product line, designed specifically for applications demanding high DC accuracy, low power, and autonomous calibration in space- and power-constrained embedded systems.
FAQ
What is the operating temperature range for the AD7856KR?
The AD7856KR is rated for operation from 0°C to +105°C ambient temperature. This commercial-extended grade differs from the A-version (–40°C to +105°C) and is validated per Analog Devices AD7856 Rev. A datasheet specifications. The AD7856KR maintains ±2 LSB integral nonlinearity and 78 dB SNR across this full range when using the internal 4.096 V reference and proper PCB layout practices.
Does the AD7856KR require external reference components?
Yes, the AD7856KR requires two external capacitors: a 0.1 µF multilayer ceramic capacitor (CREF1) and a 0.01 µF multilayer ceramic capacitor (CREF2), both connected between their respective pins (CREF1, CREF2) and AGND. These stabilize the internal reference and DAC charge redistribution network. The AD7856KR does not require an external voltage reference unless overriding the internal 4.096 V REFOUT.
How does the AD7856KR handle power management during idle periods?
The AD7856KR supports three power-down states controlled by the SLEEP pin and PMGT[1:0] bits in its control register. With SLEEP = 0 and PMGT1=1/PMGT0=0, it achieves full power-down (5 µA typ with clock off). With PMGT1=1/PMGT0=1, it enters partial power-down (200 µA typ), retaining reference and calibration memory. Automatic power-down after conversion reduces average power to 2.5 mW typ - critical for battery longevity in AD7856KR-based portable systems.
Can the AD7856KR perform system calibration with an external reference?
Yes, the AD7856KR supports system calibration using an external reference applied to the REFIN/REFOUT pin. When CALMD = 1 and STCAL = 1, the device measures system gain and offset errors relative to the external reference and updates internal calibration registers. This corrects for errors introduced by front-end amplifiers, filters, or sensor conditioning circuits - ensuring end-to-end accuracy remains within ±2 LSB for the AD7856KR even with imperfect analog signal chains.
What serial interface modes does the AD7856KR support, and how are they selected?
The AD7856KR supports two serial interface modes: Mode 1 (two-wire, DIN bidirectional) and Mode 2 (three-wire, DIN input-only). Mode selection is controlled by the 2/3 MODE bit (bit 5) in the control register: 0 = Mode 2 (default after reset), 1 = Mode 1. In Mode 1, DIN serves as both input and output, eliminating need for direction control logic; in Mode 2, separate DOUT and DIN lines simplify timing but require more GPIO resources. Both modes are compatible with SPI, QSPI, and 8051 microcontrollers.
AD7856KR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Number of Bits:
- 14
- Sampling Rate (Per Second):
- 285k
- Number of Inputs:
- -
- Input Type:
- -
- Data Interface:
- -
- Configuration:
- -
- Ratio - S/H:ADC:
- -
- Number of A/D Converters:
- 2
- Architecture:
- -
- Reference Type:
- -
- Voltage - Supply, Analog:
- -
- Voltage - Supply, Digital:
- -
- Features:
- -
- Operating Temperature:
- 0°C ~ 105°C
- Supplier Device Package:
- 24-SOIC
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
AD7856KR FAQ
1.How can I place an order for AD7856KR through Aetrix?
Please submit a Request for Quotation (RFQ) for AD7856KR 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 AD7856KR reliable?
The price and inventory of AD7856KR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD7856KR is usually 5 days.
3.What payment methods are accepted for AD7856KR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD7856KR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD7856KR?
AD7856KR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD7856KR 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 AD7856KR?
For technical support, including AD7856KR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD7856KR requirements.
6.How does Aetrix verify that AD7856KR is sourced from the original manufacturer or authorized distributors?
All AD7856KR 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 AD7856KR meets industry standards.
7.What is the process for return or replacement of AD7856KR?
All AD7856KR units undergo pre-shipment inspection (PSI). If there is an issue with AD7856KR, 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 AD7856KR part is unused and in its original packaging.
Return procedure for AD7856KR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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