Analog Devices Inc. AD7856KRZ

Overview

AD7856KRZ from Analog Devices is a 14-bit, 285 kSPS successive-approximation analog-to-digital converter (SAR ADC) operating from a single 5 V supply. It features eight single-ended or four pseudo-differential analog inputs, on-chip 4.096 V reference, self- and system calibration, and SPI/QSPI/μP-compatible serial interface - used in portable instrumentation, medical data loggers, and industrial sensor signal chains.

For engineers reviewing the AD7856KRZ datasheet, AD7856KRZ pinout, AD7856KRZ application, or AD7856KRZ equivalent, key selection considerations include its K-grade temperature range (0°C to +105°C), 24-lead SOIC package, 78 dB SNR at 10 kHz input, ±2 LSB integral nonlinearity, and flexible power-down modes enabling <2.5 mW typical operation after conversion.

Technical Context

The AD7856KRZ implements a charge redistribution SAR architecture with integrated track-and-hold, internal DAC, and calibration memory. Its analog front end supports 0 V to V_REF unipolar input range and accepts external references from 1.2 V to V_DD, while the digital core uses separate AVDD/DVDD supplies with independent AGND/DGND grounds.

It operates with a 4 MHz master clock (K grade), delivers 5.25 µs max conversion time, and supports two serial interface modes: Mode 2 (3-wire, DIN as input only) and Mode 1 (2-wire, DIN bidirectional). Calibration is initiated via dedicated CAL pin or software control register bits, with full self-calibration requiring ~62.5 ms.

Key Specifications

Pinout & Package

AD7856KRZ 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 thermal resistance θ_JA = 75°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SAR ADC applications.

Compared with AD7856ARZ, the AD7856KRZ trades extended temperature range for lower cost and reduced clock frequency headroom; versus AD7923BRUZ, it prioritizes resolution and calibration integrity over raw speed and power efficiency - making it optimal for precision measurement where 14-bit linearity and field recalibration matter most.

Availability

AD7856KRZ is available at Aetrix Electronics and suitable for portable medical instrumentation, industrial sensor signal conditioning, and battery-powered data loggers requiring stable component supply across extended product lifecycles.

Supply support for AD7856KRZ 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 AD7856KRZ belongs to Analog Devices' precision SAR ADC product line, designed specifically for applications demanding high DC accuracy, low power, and robust calibration - including portable instrumentation, industrial process control, and sensor interface modules.

FAQ

What is the operating temperature range for the AD7856KRZ?

The AD7856KRZ is rated for 0°C to +105°C ambient operation (K grade), validated per manufacturer specifications with full performance guaranteed across this range. This makes AD7856KRZ suitable for industrial enclosures and commercial-grade portable equipment but not for extended cold environments - for those, the A-grade AD7856ARZ is recommended.

Does the AD7856KRZ require external reference components?

Yes - the AD7856KRZ requires two external capacitors on CREF1 and CREF2 pins: a 0.1 µF multilayer ceramic in parallel with a 470 nF NP0 type on CREF1, and a 0.01 µF multilayer ceramic on CREF2, both referenced to AGND. These stabilize the internal DAC and reference node; omitting them degrades INL and noise performance.

How does the AD7856KRZ handle channel selection and input configuration?

The AD7856KRZ supports eight single-ended or four pseudo-differential inputs via software configuration of the Control Register's SGL/DIFF and CH2–CH0 bits. Channel selection is fully programmable - for example, writing CH2–CH0 = 000 selects AIN1 (single-ended) or AIN1–AIN2 (pseudo-differential), with no hardware changes needed.

Can the AD7856KRZ perform system calibration with an external reference?

Yes - the AD7856KRZ supports system calibration using an external reference applied to REFIN/REFOUT. When CALMD = 1 and appropriate CALSLT bits are set, the device measures offset and gain errors against the external reference and stores correction coefficients in on-chip calibration registers - enabling traceable field recalibration without test equipment.

What serial interface modes does the AD7856KRZ support, and how are they selected?

The AD7856KRZ supports two serial interface modes: Mode 2 (3-wire, DIN input-only) and Mode 1 (2-wire, DIN bidirectional). Mode selection is controlled by the 2/3 MODE bit (bit 5) in the Control Register - cleared (0) for Mode 2 (default), set (1) for Mode 1. Mode 1 requires re-setting this bit before each write cycle.