Analog Devices Inc. AD7858BR

Overview

AD7858BR from Analog Devices is a 12-bit, 200 kSPS successive-approximation ADC with eight single-ended or four pseudo-differential analog inputs, 2.5 V internal reference, and SPI/QSPI/8051-compatible serial interface - designed for battery-powered instrumentation and portable medical devices operating from 3 V to 5.5 V supply.

For engineers reviewing the AD7858BR datasheet, AD7858BR pinout, AD7858BR application, or AD7858BR equivalent, this page delivers verified electrical specs, calibrated DC accuracy (±0.5 LSB INL, B-grade), timing-critical interface behavior, and real-world power management trade-offs between speed and sleep-mode dissipation (20 mW normal / 55 µW sleep at 3.6 V).

Technical Context

The AD7858BR implements a charge-redistribution SAR architecture with integrated track-and-hold, on-chip 2.5 V reference, and self-calibration logic that executes full offset/gain calibration in 31.25 ms (4 MHz CLKIN). It supports both hardware-triggered (CONVST) and software-initiated conversions via its 14-bit control register.

Its serial interface operates in Mode 2 (SYNC-active-low framing), accepts 4 MHz SCLK, and delivers 16-bit straight-binary output with configurable read/write addressing across ADC data, status, calibration, and test registers - enabling flexible system integration without external glue logic.

Key Specifications

Pinout & Package

AD7858BR is housed in a 24-lead SOIC (R-24) package with 0.3-inch width and standard JEDEC MS-013 footprint. Pin functions are electrically validated per Analog Devices Rev. B datasheet and support mixed-signal PCB layout with separate AGND/DGND planes and dedicated CREF1/CREF2 decoupling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7858AR, the AD7858BR provides tighter DC accuracy (±0.5 LSB) at same speed and package; versus AD7490BRUZ, it trades resolution and speed for lower system cost, simpler power design, and integrated reference - making it optimal for portable, battery-constrained 12-bit applications.

Availability

AD7858BR is available at Aetrix Electronics and suitable for battery-powered medical instruments, portable data loggers, industrial process terminals, and high-speed communication modems requiring stable component supply and long-term obsolescence planning.

Supply support for AD7858BR 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 R&D and manufacturing operations worldwide.

The AD7858BR belongs to Analog Devices' precision SAR ADC product line, engineered for portable and low-power applications demanding high DC accuracy, integrated references, and robust serial interfaces - particularly where size, power, and calibration simplicity are critical.

FAQ

What is the maximum sample rate supported by the AD7858BR?

The AD7858BR achieves a maximum throughput rate of 200 kSPS with a 4.6 µs conversion time, confirmed under AVDD = DVDD = 3.0–5.5 V, fCLKIN = 4 MHz, and REFIN/REFOUT = 2.5 V. This performance is guaranteed across the full −40°C to +85°C operating range for the B-grade device. The AD7858BR maintains this rate while delivering ±0.5 LSB integral nonlinearity and 71 dB SNR, making it suitable for real-time signal capture in portable instrumentation.

Does the AD7858BR require an external reference voltage?

No, the AD7858BR includes an internal 2.5 V reference with ±20 ppm/°C temperature coefficient, available at the REFIN/REFOUT pin. It can operate fully autonomously using this reference. However, the device also accepts external references from 1.2 V to VDD, allowing flexibility for applications needing extended input ranges or improved stability - such as when paired with a precision external reference like the ADR431. The AD7858BR's reference input impedance is 150 kΩ typical.

How does the AD7858BR handle calibration, and is it required before first use?

The AD7858BR performs automatic self-calibration on power-up when a 10 nF capacitor is connected from the CAL pin to DGND. This initiates full offset and gain calibration in 31.25 ms (at 4 MHz CLKIN), storing correction data in on-chip registers. System calibration is also supported for end-equipment-level trimming. While not strictly required for basic operation - the part powers up ready to convert - calibration ensures guaranteed ±0.5 LSB INL and total unadjusted error ≤±1 LSB across temperature and time, which is essential for medical and industrial-grade accuracy.

What are the power-down modes available on the AD7858BR, and how much current do they draw?

The AD7858BR offers three programmable power-down states controlled via PMGT1/PMGT0 bits in the control register: full power-down (10 µA typ with external clock on), partial power-down (400 µA typ), and full power-down with external clock disabled (5 µA max). At 3.6 V, sleep-mode power dissipation is 36 µW - enabling ultra-low-quiescent operation in battery-powered systems. All modes retain calibration data, allowing sub-millisecond wake-up to full operation without recalibration.

Is the AD7858BR pin-compatible with other members of the AD7858 family?

Yes, all AD7858 variants - including AD7858AR, AD7858BN, AD7858LBR - share identical 24-lead SOIC (R-24) pinouts and register maps. The AD7858BR differs only in grade (B-grade INL), speed (200 kSPS), and power profile (20 mW normal mode), while maintaining full electrical and mechanical compatibility. This allows seamless substitution within the same PCB layout when upgrading accuracy or adjusting cost/performance trade-offs without redesign.