Analog Devices Inc. AD7942BRMZ

Overview

AD7942BRMZ from Analog Devices is a 14-bit, pseudo-differential successive approximation register (SAR) ADC with 250 kSPS throughput, ±1 LSB INL max, 85 dB SINAD at 20 kHz, and no pipeline delay. It operates from a single 2.3 V to 5.5 V supply, supports 1.8 V–5 V logic via separate VIO, and targets precision data acquisition in battery-powered instrumentation and medical devices.

For engineers reviewing the AD7942BRMZ datasheet, AD7942BRMZ pinout, AD7942BRMZ application, or AD7942BRMZ equivalent, this page delivers verified electrical specifications, validated MSOP/LFCSP package mapping, confirmed daisy-chain SPI interface behavior, real-world power consumption at 100 SPS/100 kSPS/250 kSPS, and pin-for-pin compatibility with AD7685 for drop-in 16-bit upgrade paths.

Technical Context

The AD7942BRMZ uses a charge redistribution SAR architecture with integrated track-and-hold, enabling true single-cycle conversion without latency. Its pseudo-differential input accepts 0 V to VREF across IN+ and IN−, where VREF is externally applied up to VDD, and CMRR reaches 65 dB at 250 kHz.

It implements a proprietary SPI-compatible serial interface supporting both CS mode (with busy indicator) and chain mode (daisy-chaining multiple ADCs), synchronized by SCK with timing fully specified for VIO from 1.8 V to 5 V. Aperture delay is 2.5 ns at 5 V, and transient response to full-scale step is 1.8 μs.

Key Specifications

Pinout & Package

AD7942BRMZ is available in a 10-lead MSOP (3 mm × 3 mm) and a 10-lead LFCSP (3 mm × 3 mm), both with exposed paddle connected to GND. The package footprint matches 8-lead MSOP/SOT-23 layouts, enabling compact PCB design.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 14-bit SAR ADC applications.

Compared with AD7942BRMZ, AD7685BRMZ offers 2 extra bits at identical speed and footprint but consumes more power, while ADS8860IDRCT trades daisy-chain capability for higher throughput and lower power per sample-making each alternative optimal only under specific resolution, speed, or system-architecture constraints.

Availability

AD7942BRMZ is available at Aetrix Electronics and suitable for battery-powered equipment, medical instruments, industrial process controls, and portable instrumentation requiring stable component supply across extended temperature ranges (−40°C to +85°C).

Supply support for AD7942BRMZ 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 Norwood, MA.

The AD7942BRMZ belongs to Analog Devices' PulSAR® family of precision SAR ADCs, designed specifically for low-power, high-accuracy data acquisition in space-constrained and energy-sensitive applications.

FAQ

What is the maximum recommended reference voltage for AD7942BRMZ?

The AD7942BRMZ supports an external reference voltage (REF) from 0.5 V up to VDD. When VDD = 5.5 V, VREF may be as high as 5.5 V; however, the datasheet specifies optimal AC performance (e.g., 85 dB SINAD) at VREF = 5 V. Using VREF = VDD simplifies supply design but requires ensuring VDD stability, as reference noise directly impacts ADC accuracy. For best results, decouple REF with a 10 µF X5R ceramic capacitor placed adjacent to the REF pin.

Does AD7942BRMZ require an external clock source for conversion?

No, AD7942BRMZ does not require an external clock for conversion. It contains an internal conversion clock, so the SCK signal is used solely for serial data readout-not for controlling the sampling or conversion process. The CNV rising edge initiates conversion independently, and the result becomes available after tCONV (≤2.2 μs at 5 V). This architecture eliminates timing dependency on host SCK frequency and enables deterministic conversion start times critical for synchronized multi-channel sampling.

Can AD7942BRMZ operate with a 1.8 V digital interface while using a 5 V analog supply?

Yes, AD7942BRMZ supports independent analog and digital supplies: VDD = 5 V powers the ADC core and reference path, while VIO = 1.8 V sets logic thresholds for SDI, SCK, SDO, and CNV. This separation allows direct interfacing with 1.8 V FPGAs or microcontrollers without level-shifting circuitry. The device maintains full specification compliance-including timing (e.g., tSCK ≥ 20 ns at VIO = 1.8 V) and logic level thresholds (VIH = 0.7 × VIO)-ensuring robust communication across mixed-voltage systems.

What is the purpose of the IN− pin on AD7942BRMZ?

The IN− pin on AD7942BRMZ serves as the pseudo-differential ground sense reference-not a true differential input pair. It establishes the common-mode baseline for the IN+ signal, enabling rejection of noise coupled equally to both pins. Connecting IN− to a remote sensor ground (rather than local PCB ground) eliminates ground potential differences in long-cable sensor interfaces. The analog input range is defined as (IN+ − IN−) = 0 V to VREF, and IN− must remain within −0.1 V to +0.1 V to avoid violating absolute maximum ratings.

Is AD7942BRMZ pin-compatible with any other Analog Devices ADCs?

Yes, AD7942BRMZ is explicitly pin-for-pin compatible with the 16-bit AD7685BRMZ in both 10-lead MSOP and LFCSP packages. This allows hardware reuse in designs where resolution can be upgraded without PCB revision. Both share identical pin functions, timing behavior, and interface modes (CS and daisy-chain). However, AD7685BRMZ draws higher supply current (7 mW vs. 3.6 mW at 5 V/100 kSPS) and exhibits different AC specs (e.g., −105 dB THD), so firmware and layout validation remain necessary despite mechanical compatibility.