Analog Devices Inc. AD7938BSU-6

Overview

AD7938BSU-6 from Analog Devices is a 12-bit, 8-channel, 625 kSPS successive approximation register (SAR) analog-to-digital converter with integrated channel sequencer and on-chip 2.5 V reference. It operates from a single 2.7 V to 5.25 V supply, supports single-ended/pseudo-differential/differential input configurations, and delivers 69 dB SINAD at 50 kHz - enabling high-fidelity data acquisition in multichannel industrial sensor systems.

For engineers reviewing the AD7938BSU-6 datasheet, AD7938BSU-6 pinout, AD7938BSU-6 application, or AD7938BSU-6 equivalent, key selection considerations include its parallel interface with word/byte mode support, VDRIVE-independent logic level control, no pipeline delay, autostandby power management, and 32-lead TQFP package compatibility for space-constrained embedded designs.

Technical Context

The AD7938BSU-6 implements a differential track-and-hold amplifier with 50 MHz full-power bandwidth and aperture jitter of 72 ps, enabling accurate sampling of high-frequency analog signals. Its sequencer allows preprogrammed conversion sequences across all eight inputs without host intervention.

Conversion is initiated by a falling edge on CONVST, with timing controlled by a 10 MHz master clock (CLKIN); total conversion time is t₂ + 13 × t_CLKIN. The device uses a flexible parallel interface with CS/RD/WR control, BUSY status signaling, and W/B-selectable 12-bit word or byte transfer modes - directly interfacing with microprocessors and DSPs without glue logic.

Key Specifications

Pinout & Package

AD7938BSU-6 is housed in a 32-lead TQFP (SU-32-2) package with exposed pad. Pin 1 identifier and EPAD must be connected to AGND/DGND plane via multiple vias per Analog Devices layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7938BCPZ-6, AD7938BSU-6 offers superior manufacturability and thermal robustness in industrial assemblies; compared with AD7934-6, it provides essential 8-channel sequencing for scalable sensor networks - making AD7938BSU-6 the optimal choice for general-purpose multichannel data acquisition where layout flexibility and channel agility are prioritized.

Availability

AD7938BSU-6 is available at Aetrix Electronics and suitable for industrial process monitoring, motor control feedback, portable power quality analyzers, medical sensor hubs, and battery-powered test equipment requiring stable component supply and long-term production continuity.

Supply support for AD7938BSU-6 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 AD7938 product line delivers high-speed, low-power, multichannel SAR ADCs optimized for precision data acquisition in industrial automation, energy metering, and medical instrumentation - emphasizing configurability, integration, and ease of microprocessor interfacing.

FAQ

What is the maximum sampling rate supported by the AD7938BSU-6?

The AD7938BSU-6 supports a maximum throughput rate of 625 kSPS under specified conditions (f_CLKIN = 10 MHz, VDD = 2.7 V to 5.25 V). This rate is achieved with a conversion time of t₂ + 13 × t_CLKIN, and the device maintains 69 dB SINAD at 50 kHz input frequency in differential mode. Lower clock frequencies reduce throughput proportionally but retain full DC accuracy specifications.

Does the AD7938BSU-6 require an external reference voltage?

No, the AD7938BSU-6 includes an accurate on-chip 2.5 V reference (±0.2% max at 25°C, 25 ppm/°C tempco) that can be used directly as the conversion reference. The VREFIN/VREFOUT pin may be overdriven with an external reference between 0.1 V and VDD if higher precision or custom full-scale range is required - but external reference is optional, not mandatory, for AD7938BSU-6 operation.

How does the sequencer function in the AD7938BSU-6?

The AD7938BSU-6 sequencer enables preprogrammed, automatic conversion of up to eight analog input channels in user-defined order without host processor intervention. Channel selection is configured via the control register's SEQ and address bits (ADD2–ADD0); once enabled, the sequencer cycles through designated channels sequentially on each CONVST trigger - reducing firmware overhead and ensuring deterministic timing in cyclic acquisition tasks.

What are the supported analog input configurations for the AD7938BSU-6?

The AD7938BSU-6 supports three analog input topologies via software configuration: eight single-ended inputs (VIN0–VIN7 referenced to AGND), four fully differential pairs (e.g., VIN0+/VIN0−), or four/seven pseudo-differential inputs (e.g., VIN0+ referenced to VIN1−). Configuration is controlled by MODE bits in the control register, and input range (0–VREF or 0–2×VREF) and coding (straight binary or twos complement) are independently selectable.

Can the AD7938BSU-6 interface directly with a 3 V microcontroller while operating from a 5 V analog supply?

Yes, the AD7938BSU-6 supports independent logic and analog supplies via the VDRIVE pin. When VDRIVE is set to 3 V and VDD to 5 V, the parallel interface (DB0–DB11, RD, WR, CS, etc.) operates at 3 V logic levels while the analog core runs at 5 V - enabling direct connection to 3 V microcontrollers without level shifters. This separation is explicitly designed into the AD7938BSU-6 architecture and verified in the datasheet timing and interface specifications.