Analog Devices Inc. AD7858LBRZ

Overview

AD7858LBRZ from Analog Devices is a 12-bit, 100 kSPS SAR analog-to-digital converter with eight single-ended or four pseudo-differential analog inputs, internal reference buffer, and flexible SPI/QSPI/μP-compatible serial interface. It operates from a single 3 V to 5.5 V supply, consumes 4.5 mW at 3 V, and features automatic power-down after conversion and on-chip self-calibration. It is used in battery-powered instrumentation and portable medical devices requiring precision, low power, and compact size.

For engineers reviewing the AD7858LBRZ datasheet, AD7858LBRZ pinout, AD7858LBRZ application, or AD7858LBRZ equivalent, this page delivers verified technical context, real-world timing behavior, calibrated DC accuracy specs (±1 LSB INL), true channel isolation (–90 dB), and validated alternative options for low-power 12-bit ADC selection in space- and energy-constrained systems.

Technical Context

The AD7858LBRZ implements a charge-redistribution SAR architecture with integrated track-and-hold, internal 2.5 V reference buffer, and programmable calibration engine supporting both system and self-calibration. Its 500 ns track/hold acquisition time enables accurate sampling of full-scale signals up to 100 kHz.

It uses a 24-pin SOIC package with separate analog/digital supplies (AVDD/DVDD) and grounds (AGND/DGND), supports external clock input (CLKIN = 1 MHz max for –40°C to +85°C), and provides three power management modes-normal, partial, and full power-down-with sub-µW sleep current when CLKIN is off.

Key Specifications

Pinout & Package

AD7858LBRZ is housed in a 24-lead SOIC (R-24) package with 0.3-inch body width, gull-wing leads, and standard JEDEC MS-013AC footprint. Pin 1 is marked by a beveled corner or dot; pin numbering follows counterclockwise convention from top-left.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7822U and MAX11131ETE+, the AD7858LBRZ uniquely combines 12-bit accuracy, on-chip self/system calibration, pseudo-differential input flexibility, and ultra-low 4.5 mW active power - making it optimal for battery-operated instruments where long-term measurement stability and minimal BOM count are critical.

Availability

AD7858LBRZ is available at Aetrix Electronics and suitable for battery-powered medical instrumentation, portable industrial data loggers, pen-based computing interfaces, and high-speed modem analog front ends requiring stable component supply, long-lifecycle support, and traceable sourcing.

Supply support for AD7858LBRZ 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 AD7858LBRZ belongs to Analog Devices' legacy precision SAR ADC product line, designed specifically for portable, low-power, multi-channel data acquisition systems where calibration integrity, supply flexibility, and small-footprint integration are essential.

FAQ

What is the maximum clock frequency supported by AD7858LBRZ?

The AD7858LBRZ supports a maximum CLKIN frequency of 1 MHz over its full operating temperature range (–40°C to +85°C). At 0°C to +70°C, the B-grade version permits up to 1.8 MHz. This clock sets conversion timing: t_CONVERT = 18 × t_CLKIN, yielding 10 µs max conversion time at 1 MHz. Exceeding these limits risks timing violations and invalid conversion results in the AD7858LBRZ.

Does AD7858LBRZ require external reference components?

Yes, the AD7858LBRZ requires two external capacitors: a 0.1 µF multilayer ceramic capacitor (CREF1) and a 0.01 µF ceramic disc capacitor (CREF2), both connected between their respective pins (Pins 7 and 8) and AGND. These stabilize the internal reference buffer and DAC charge redistribution network. Omitting either capacitor degrades SNR and causes gain drift in the AD7858LBRZ.

Can AD7858LBRZ perform system calibration with an external reference?

Yes, the AD7858LBRZ supports system calibration using an external reference applied to REFIN/REFOUT (Pin 4). Its calibration engine accommodates offset spans of ±0.05 × V_REF and gain spans of +1.025/–0.975 × V_REF. When using an external reference, CREF1 and CREF2 remain mandatory, and the system full-scale voltage must fall within the calibrated span to ensure valid correction in the AD7858LBRZ.

What is the function of the CAL pin on AD7858LBRZ?

The CAL pin (Pin 17) is an active-high calibration trigger with internal 0.15 µA pull-up. A rising edge initiates full self-calibration; tying a 10 nF capacitor from CAL to DGND enables automatic calibration on power-up. During calibration, BUSY goes high and remains asserted for ~31.25 ms (at 1 MHz CLKIN). The AD7858LBRZ retains calibration coefficients in nonvolatile memory until next CAL assertion.

How does AD7858LBRZ handle power-down sequencing?

The AD7858LBRZ offers three power-down states controlled by PMGT1/PMGT0 bits in its control register: normal (PMGT=00), partial (PMGT=11), and full (PMGT=10). Full power-down draws 5 µA max with CLKIN off and retains calibration data. SLEEP pin (Pin 3) provides hardware override: logic 0 forces immediate full power-down regardless of register settings, and logic 1 restores normal operation - critical for rapid wake-up in the AD7858LBRZ.