Analog Devices Inc. AD7858AR

Overview

AD7858AR from Analog Devices is a 12-bit, 200 kSPS SAR analog-to-digital converter with eight single-ended or four pseudo-differential input channels, internal reference buffer, and flexible SPI/QSPI/8051-compatible serial interface - designed for high-accuracy data acquisition in battery-powered instrumentation and portable medical devices operating from 3 V to 5.5 V.

For engineers reviewing the AD7858AR datasheet, AD7858AR pinout, AD7858AR application, or AD7858AR equivalent, this page delivers verified specifications, calibrated DC accuracy (±1 LSB INL), timing-critical interface behavior, power-down modes (25 µW sleep), and real-world channel isolation (–90 dB) - all confirmed for the R-24 SOIC package variant.

Technical Context

The AD7858AR implements a charge-redistribution SAR architecture with integrated track-and-hold (500 ns acquisition), on-chip 2.5 V reference buffer (REFIN/REFOUT), and dual-domain power supplies (AVDD/DVDD). It supports system-level calibration via dedicated CAL pin and control register–driven self-calibration sequences.

Its serial interface operates in Mode 2 (SYNC-active-low framing), supports 4 MHz master clock (CLKIN), and delivers 16-bit read/write words with configurable register addressing (Control, ADC Output Data, Status, Calibration). Conversion is initiated by CONVST edge or software write, with BUSY signaling completion.

Key Specifications

Pinout & Package

AD7858AR is housed in a 24-lead SOIC (R-24) package with standard 0.3-inch width, JEDEC MS-013AC compliant footprint, and 1.27 mm lead pitch - suitable for automated PCB assembly and thermal management in space-constrained designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit SAR ADC applications.

Compared with AD7858BR, AD7858AR trades 0.5 LSB INL tolerance for broader availability and lower unit cost; compared with AD7858LAR, it doubles throughput at 3× higher active power - making AD7858AR the default choice for 200 kSPS, A-grade industrial data acquisition.

Availability

AD7858AR is available at Aetrix Electronics and suitable for portable medical instrumentation, battery-powered data loggers, and industrial process monitoring requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD7858AR 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, headquartered in Norwood, MA, with design centers worldwide.

The AD7858AR belongs to Analog Devices' precision SAR ADC product line, engineered for high-resolution, low-power data acquisition in portable and embedded systems where accuracy, power efficiency, and integration are critical.

FAQ

What is the maximum sample rate supported by the AD7858AR?

The AD7858AR supports a maximum throughput rate of 200 kSPS under standard operating conditions (4 MHz CLKIN, AVDD = DVDD = 3.0–5.5 V). This enables accurate digitization of signals with up to 100 kHz bandwidth while maintaining 71 dB SNR and –78 dB THD performance as specified in the datasheet.

Does the AD7858AR require an external reference voltage?

No - the AD7858AR features an internal 2.5 V reference buffer accessible via the REFIN/REFOUT pin, which can serve as the conversion reference. However, it also supports external references from 1.2 V to AVDD, allowing flexibility for systems requiring different full-scale ranges or higher precision references.

How does the AD7858AR handle power management in battery-operated systems?

The AD7858AR provides three low-power states: automatic post-conversion shutdown (25 µW), full power-down (5 µA with external clock off), and partial power-down (200 µA). These modes are controlled via PMGT bits in the control register or the SLEEP pin, enabling precise energy budgeting in portable applications.

Can the AD7858AR interface directly with an 8051 microcontroller?

Yes - the AD7858AR's serial interface is explicitly designed to be 8051-compatible in addition to SPI and QSPI protocols. It uses SYNC framing, supports 4 MHz SCLK, and requires no level-shifting when interfaced with 3 V or 5 V 8051 derivatives, simplifying firmware integration.

What is the purpose of the CAL pin on the AD7858AR?

The CAL pin on the AD7858AR initiates on-chip self-calibration on its rising edge. With a 10 nF capacitor tied from CAL to DGND, it enables automatic calibration at power-up. This ensures ±1 LSB INL accuracy across temperature and time without host processor intervention - critical for unattended field-deployed systems.