Analog Devices Inc. AD7858ARZ

Overview

AD7858ARZ 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/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 supports system/self-calibration for precision measurement in portable instrumentation.

For engineers reviewing the AD7858ARZ datasheet, AD7858ARZ pinout, AD7858ARZ application, or AD7858ARZ equivalent, key selection criteria include its 24-lead SOIC package, 4.6 μs conversion time, ±1 LSB integral nonlinearity (B-grade), 12 mW power dissipation at 3 V, and support for autocalibration on power-up - all critical for battery-powered data acquisition systems requiring stable DC accuracy and low idle current.

Technical Context

The AD7858ARZ implements a charge-redistribution SAR architecture with integrated track-and-hold, 2.5 V buffered reference, and on-chip calibration memory. Its control logic supports software-initiated conversions via register writes and hardware-triggered acquisition using CONVST, with BUSY signaling completion.

It features dual power domains (AVDD/DVDD), configurable power management (PMGT bits), and a 16-bit serial interface supporting Mode 2 timing with SYNC framing. The device accepts external clock inputs (CLKIN) up to 4 MHz and provides straight binary output coding over 0 V to VREF input range.

Key Specifications

Pinout & Package

AD7858ARZ is housed in a 24-lead SOIC (R-24) package with standard 0.3-inch width and 0.025-inch lead pitch. Thermal impedance is 75°C/W (θJA), suitable for industrial ambient conditions 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 AD7858ARZ, AD7858BRZ offers improved DC accuracy without trade-offs in speed or interface, while AD7858LARZ sacrifices half the sampling rate to achieve >40% lower power - making each variant optimal for distinct design constraints in portable and embedded measurement systems.

Availability

AD7858ARZ is available at Aetrix Electronics and suitable for portable medical instrumentation, industrial data loggers, pen-based computing interfaces, and high-speed modem signal conditioning requiring stable component supply and long-term manufacturability.

Supply support for AD7858ARZ 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.

The AD7858ARZ belongs to Analog Devices' precision SAR ADC product line, designed specifically for portable and low-power measurement systems requiring integrated calibration, flexible serial interfaces, and guaranteed DC accuracy without external support components.

FAQ

What is the maximum sampling rate supported by the AD7858ARZ?

The AD7858ARZ supports a maximum throughput rate of 200 kSPS under standard operating conditions with a 4 MHz master clock. This corresponds to a minimum conversion time of 4.6 μs and enables accurate digitization of input signals up to 100 kHz (Nyquist limit). The AD7858ARZ achieves this performance while maintaining 71 dB SNR and ±1 LSB integral nonlinearity, making it suitable for high-fidelity data acquisition applications where both speed and precision are required.

Does the AD7858ARZ require an external reference voltage?

No, the AD7858ARZ does not require an external reference voltage because it includes an internal 2.5 V buffered reference accessible via the REFIN/REFOUT pin. However, the device supports external reference override from 1.2 V to AVDD, allowing system designers to substitute higher-accuracy or temperature-stable references when needed. When using the internal reference, external capacitors CREF1 (0.1 μF) and CREF2 (0.01 μF) must be connected to AGND per the AD7858ARZ layout guidelines to ensure stability and noise rejection.

How does the AD7858ARZ handle calibration during operation?

The AD7858ARZ supports both self-calibration and system calibration modes initiated via the CAL pin or control register. A rising edge on CAL triggers full self-calibration (typ. 31.25 ms at 4 MHz CLKIN), correcting internal DAC and comparator offsets. System calibration allows users to apply known reference signals to adjust for external gain/offset errors. Calibration data is retained during SLEEP mode, and autocalibration can be enabled on power-up using a 10 nF capacitor from CAL to DGND - ensuring consistent accuracy across power cycles without host intervention.

What serial interface protocols are compatible with the AD7858ARZ?

The AD7858ARZ features a versatile 16-bit serial interface compatible with SPI, QSPI, and 8051 microcontroller protocols. It operates in Mode 2 (CPOL = 1, CPHA = 0) with active-low SYNC framing, supporting both read and write operations during or after conversion. The interface includes DIN (data in), DOUT (data out), SCLK (serial clock), and SYNC (frame sync) pins, and allows software-configurable power management and channel selection through its control register - eliminating the need for additional glue logic in μC-based systems.

What is the power consumption of the AD7858ARZ in sleep mode?

In full power-down sleep mode with external clock disabled, the AD7858ARZ draws a maximum of 5 µA (typically 1 µA) from DVDD and AVDD combined, resulting in total power dissipation below 18 µW at 3.6 V. This ultra-low standby current enables extended battery life in intermittent-sampling applications. The device retains calibration data and register settings during sleep, and resumes normal operation within microseconds upon assertion of CONVST or exit from SLEEP=0 - making it ideal for duty-cycled sensor nodes and portable diagnostic equipment.