Analog Devices Inc. AD7859APZ

Overview

AD7859APZ from Analog Devices is a high-speed, low-power, 8-channel, 12-bit successive approximation register (SAR) analog-to-digital converter (ADC) operating from a single 3 V to 5.5 V supply. It delivers 200 kSPS throughput, features on-chip self- and system calibration, supports unipolar (0 to VREF) and bipolar (±VREF/2) input ranges, and uses a flexible 16-bit or 8-bit parallel interface for embedded data acquisition in portable instrumentation.

For engineers reviewing the AD7859APZ datasheet, AD7859APZ pinout, AD7859APZ application, or AD7859APZ equivalent, key selection criteria include its 12-bit resolution with ±1 LSB INL, 70 dB SNR at 10 kHz, 500 ns track/hold acquisition time, PQFP-44 package compatibility, and support for both 3 V and 5 V logic-level interfacing in battery-constrained systems.

Technical Context

The AD7859APZ integrates a charge redistribution DAC, pseudo-differential input multiplexer, and track-and-hold amplifier optimized for fast settling (500 ns). Its internal calibration memory and controller enable automatic offset/gain correction across temperature and time without external components.

It employs a 4 MHz master clock (CLKIN) to achieve 4.5 µs conversion time (18 × t_CLKIN) and supports three power-down modes via PMGT1/PMGT0 bits and SLEEP pin - full power-down (5 µA), partial power-down (200 µA), and automatic post-conversion sleep (1.3 mW at 10 kSPS).

Key Specifications

Pinout & Package

The AD7859APZ is housed in a 44-pin plastic quad flatpack (PQFP) package with 0.8 mm lead pitch and exposed thermal pad (not electrically connected). Pin 1 is marked by a corner notch or dot; pins are numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7859AS and AD7859BS, the AD7859APZ offers identical speed, power, and interface functionality but includes lead-free (Pb-free) terminations and enhanced moisture sensitivity packaging (MSL3), making it suitable for modern automated SMT lines while maintaining full drop-in compatibility in existing designs.

Availability

AD7859APZ is available at Aetrix Electronics and suitable for portable medical instrumentation, battery-powered data loggers, pen-based computing interfaces, and industrial process monitoring requiring stable component supply across extended production lifecycles.

Supply support for AD7859APZ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Wilmington, MA.

The AD7859APZ belongs to Analog Devices' precision SAR ADC product line, designed specifically for low-power, multi-channel data acquisition in portable and embedded systems where accuracy, speed, and supply flexibility are critical.

FAQ

What is the maximum sampling rate supported by the AD7859APZ?

The AD7859APZ supports a maximum throughput rate of 200 kSPS, achieved with a 4 MHz master clock (CLKIN) and 4.5 µs conversion time (18 × t_CLKIN). This rate is maintained across the full operating temperature range (–40°C to +85°C) and supply range (3.0 V to 5.5 V), enabling real-time capture of signals up to ~80 kHz without aliasing. The AD7859APZ does not support oversampling or decimation modes beyond this fixed rate.

Does the AD7859APZ require external reference components?

Yes, the AD7859APZ requires two external capacitors connected to AGND: a 0.1 µF multilayer ceramic capacitor on CREF1 and a 0.01 µF ceramic disc capacitor on CREF2. These stabilize the internal 2.5 V reference and support charge redistribution during conversion. While the device provides a 2.5 V REFOUT, it cannot operate without these externally mounted capacitors - omission causes reference instability and degraded INL/SNR performance in the AD7859APZ.

How does the AD7859APZ handle analog input polarity selection?

The AD7859APZ supports both unipolar (0 to VREF) and bipolar (±VREF/2) input ranges via the AMODE bit in the control register. When SGL/DIFF = 0 (pseudo-differential mode), AMODE = 0 selects unipolar range and AMODE = 1 selects bipolar range, with AIN(–) biased to +VREF/2. In single-ended mode (SGL/DIFF = 1), AMODE selects the AIN(–) reference source (AGND or AIN8). This dual-mode flexibility is fully programmable and retained across power cycles in the AD7859APZ.

Can the AD7859APZ perform system-level calibration?

Yes, the AD7859APZ supports both self-calibration (internal DAC and reference) and system calibration (external gain/offset errors) via the CAL pin or CALMD bit in the control register. System calibration corrects for errors introduced by front-end signal conditioning - such as op-amp offset or resistor divider mismatch - using user-provided reference voltages. The AD7859APZ allows system offset calibration span of ±0.05 × VREF and system gain calibration span of +1.025/–0.975 × VREF, verified across temperature.

What power-down modes are available on the AD7859APZ?

The AD7859APZ offers three distinct power-down modes controlled by PMGT1/PMGT0 bits and the SLEEP pin: full power-down (5 µA, clock off), partial power-down (200 µA, clock on), and automatic post-conversion sleep (1.3 mW at 10 kSPS). All modes retain register contents and calibration data. Power state transitions occur within one CLKIN cycle, and wake-up latency is negligible - essential for duty-cycled operation in battery-powered AD7859APZ deployments.