Analog Devices Inc. AD7858BNZ

Overview

AD7858BNZ from Analog Devices is a 12-bit, 200 kSPS SAR analog-to-digital converter with eight single-ended or four pseudo-differential inputs, internal reference buffer, system/self-calibration, and SPI/QSPI/μP-compatible serial interface. It operates from a single 3 V to 5.5 V supply, delivers 71 dB SNR at 10 kHz input, and targets precision data acquisition in battery-powered instrumentation.

For engineers reviewing the AD7858BNZ datasheet, AD7858BNZ pinout, AD7858BNZ application, or AD7858BNZ equivalent, key selection factors include its 200 kSPS throughput, ±1 LSB integral nonlinearity (B-grade), 24-lead PDIP package, automatic power-down after conversion (25 μW sleep), and support for external reference voltages from 1.2 V to VDD.

Technical Context

The AD7858BNZ employs a charge-redistribution SAR architecture with integrated track-and-hold, calibrated DAC, and on-chip calibration memory. Its functional block includes a programmable input multiplexer, 2.5 V buffered reference path (REFIN/REFOUT), and dual-domain power supplies (AVDD/DVDD) enabling analog/digital domain isolation.

It supports two serial interface modes via SYNC/SCLK/DIN/DOUT, with timing governed by CLKIN (4 MHz max) and CONVST-triggered conversion. Calibration is initiated by CAL pin or control register, covering offset, gain, and full-system error correction - all retained across sleep cycles without recalibration.

Key Specifications

Pinout & Package

AD7858BNZ is housed in a 24-lead plastic DIP (N-24) package with 0.3-inch width, through-hole mounting, and industry-standard pin spacing. Thermal impedance θ_JA = 105°C/W supports operation up to +85°C ambient without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7858LANZ and ADS7822U, the AD7858BNZ uniquely balances high-speed acquisition, on-chip calibration, pseudo-differential flexibility, and DIP packaging - making it optimal for prototyping, industrial test equipment, and legacy-compatible upgrades where layout stability and feature completeness outweigh minimal cost savings.

Availability

AD7858BNZ is available at Aetrix Electronics and suitable for battery-powered medical instruments, portable data loggers, industrial process transmitters, and high-speed modem analog front-ends requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for AD7858BNZ 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 AD7858BNZ belongs to Analog Devices' precision SAR ADC product line, engineered for applications demanding high DC accuracy, low power, and robust serial interfacing in harsh or portable environments.

FAQ

What is the maximum sampling rate supported by the AD7858BNZ?

The AD7858BNZ supports a maximum sampling rate of 200 kSPS under standard operating conditions (CLKIN = 4 MHz, AVDD = DVDD = 3.0–5.5 V). This throughput is achievable using the "read during conversion" timing mode shown in Figure 3 of the datasheet, which overlaps data transfer with conversion to avoid idle cycles. The AD7858BNZ maintains this rate across its full industrial temperature range (–40°C to +85°C) and guarantees timing compliance with t_CONVERT ≤ 4.6 μs.

Does the AD7858BNZ require an external reference voltage?

No - the AD7858BNZ includes an internal 2.5 V reference accessible via the REFIN/REFOUT pin, eliminating the need for an external reference in most applications. However, it also supports external references from 1.2 V to VDD, allowing users to optimize dynamic range or noise performance. When using the internal reference, CREF1 (0.1 μF) and CREF2 (0.01 μF) capacitors must be connected to AGND as specified in the pin descriptions. The AD7858BNZ remains fully functional with either configuration.

How does calibration work on the AD7858BNZ, and is it mandatory?

Calibration on the AD7858BNZ includes both self-calibration (correcting internal DAC and comparator offsets) and system calibration (compensating for external gain/offset errors). It can be triggered manually via the CAL pin or programmed via the control register. While not mandatory for basic operation - the part powers up ready to convert in read-only mode - calibration is recommended for maintaining ±1 LSB INL over temperature and time. Calibration coefficients are stored in on-chip memory and retained during SLEEP mode, so recalibration is only needed after significant environmental shifts or long-term drift.

Can the AD7858BNZ interface directly with an 8051 microcontroller?

Yes - the AD7858BNZ features a versatile serial interface explicitly designed for 8051 compatibility, in addition to SPI and QSPI modes. It uses standard signals (SYNC, SCLK, DIN, DOUT) with timing parameters aligned to 8051 bus cycles. The control register allows configuration of interface mode, read/write direction, and power management - all controllable via standard 8051 GPIO and timer peripherals. No level-shifting or protocol translation is required when interfacing with 3.3 V or 5 V 8051 derivatives.

What package type is used for the AD7858BNZ, and is it RoHS-compliant?

The AD7858BNZ is supplied in a 24-lead plastic DIP (dual-in-line package), designated N-24 in Analog Devices' ordering guide. This through-hole package has 0.3-inch body width and standard 0.1-inch pin pitch. Per Analog Devices' official product documentation and packaging data, the AD7858BNZ is RoHS-compliant and lead-free, meeting EU Directive 2011/65/EU requirements. The device carries the "N" suffix per ADI's naming convention, confirming its PDIP packaging and commercial-grade temperature rating (–40°C to +85°C).