Analog Devices Inc. AD7938BCPZ

Overview

AD7938BCPZ from Analog Devices is a 12-bit, 8-channel, 1.5 MSPS successive approximation register (SAR) ADC with integrated channel sequencer, on-chip 2.5 V reference (±0.2% @ 25°C), and parallel word/byte interface. It operates from a single 2.7 V to 5.25 V supply, consumes 6 mW at 3 V/1.5 MSPS, and supports single-ended, pseudo-differential, and fully differential input configurations for industrial data acquisition and real-time control systems.

For engineers reviewing the AD7938BCPZ datasheet, AD7938BCPZ pinout, AD7938BCPZ application, or AD7938BCPZ equivalent, key selection considerations include its 12-bit resolution with ±1 LSB INL (differential mode), 69 dB SINAD at 50 kHz, no pipeline delay, VDRIVE-enabled 3 V/5 V logic compatibility, and LFCSP-32 package with exposed thermal pad.

Technical Context

The AD7938BCPZ implements a SAR architecture with a differential track-and-hold amplifier supporting up to 50 MHz full-power bandwidth. Its sequencer enables preprogrammed, software-configurable conversion of up to eight analog inputs without host intervention.

Conversion is triggered by a falling edge on CONVST, with timing controlled by a 25.5 MHz master clock (CLKIN); total conversion time is t₂ + 13 × t_CLKIN. The parallel interface operates in word mode (12-bit DB0–DB11) or byte mode (DB0–DB7 + DB8/HBEN), with BUSY indicating conversion status and W/B selecting byte/word access.

Key Specifications

Pinout & Package

AD7938BCPZ is housed in a 32-lead LFCSP (Lead Frame Chip Scale Package) with an exposed thermal pad requiring PCB connection via multiple vias to AGND/DGND plane for optimal thermal and noise performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed SAR ADC applications.

Compared with AD7938BCPZ, AD7939BCPZ trades resolution and dynamic performance for lower cost in pin-compatible form, while AD7606C-16 adds precision and features at the expense of power and layout compatibility-making AD7938BCPZ optimal for 12-bit, low-latency, low-power industrial sampling where reference stability and sequencer autonomy are critical.

Availability

AD7938BCPZ is available at Aetrix Electronics and suitable for industrial PLC analog input modules, motor drive current sensing, portable power quality analyzers, and multi-sensor environmental monitoring nodes requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for AD7938BCPZ 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The AD7938BCPZ belongs to Analog Devices' precision SAR ADC product line, engineered for high-speed, low-power, multi-channel data acquisition in industrial automation, energy systems, and test equipment where timing determinism and reference stability are essential.

FAQ

What is the maximum sampling rate supported by the AD7938BCPZ?

The AD7938BCPZ supports a maximum throughput rate of 1.5 MSPS, achieved with a 25.5 MHz master clock (CLKIN) and 13-clock-cycle conversion time. This rate is maintained across its full operating temperature range (−40°C to +85°C) and supply voltage range (2.7 V to 5.25 V), making AD7938BCPZ suitable for real-time control loop sampling in demanding industrial environments.

Does the AD7938BCPZ require an external reference, or does it include an internal one?

The AD7938BCPZ integrates a highly accurate 2.5 V reference with ±0.2% initial error at 25°C and a maximum temperature coefficient of 25 ppm/°C. This internal reference is available at the VREFIN/VREFOUT pin and can be used directly for conversion. Alternatively, the pin accepts an external reference from 0.1 V to VDD, allowing AD7938BCPZ to adapt to system-level reference architectures without modification.

How does the channel sequencer in the AD7938BCPZ operate?

AD7938BCPZ's on-chip sequencer enables autonomous, preprogrammed conversion of up to eight analog inputs in user-defined order. Sequencing is configured via the control register and executed without host processor intervention-reducing software overhead and ensuring deterministic timing between channel samples. This feature is especially valuable in AD7938BCPZ-based data loggers and multi-sensor monitoring systems.

What package type is used for the AD7938BCPZ, and what are its thermal requirements?

The AD7938BCPZ uses a 32-lead LFCSP (CP-32-7) package with an exposed thermal pad on the underside. To ensure reliable operation and optimal thermal performance, the exposed pad must be soldered to the PCB ground plane using multiple thermal vias. Its θ_JA is 108.2°C/W, so proper thermal design is essential when operating near maximum power dissipation (6 mW at 3 V).

Can the AD7938BCPZ interface directly with both 3 V and 5 V microprocessors?

Yes-the AD7938BCPZ incorporates a dedicated VDRIVE pin that independently sets the logic interface voltage. When VDRIVE is tied to 3 V, the parallel data bus (DB0–DB11), control inputs (CS, RD, WR), and outputs (BUSY) operate at 3 V logic levels-even if VDD is 5 V. This eliminates level shifters and simplifies interconnection with mixed-voltage systems, a key advantage of AD7938BCPZ in heterogeneous embedded platforms.