Analog Devices Inc. AD7938BCP-6

Overview

AD7938BCP-6 from Analog Devices is a 12-bit, 8-channel, 625 kSPS successive approximation register (SAR) ADC with integrated channel sequencer, on-chip 2.5 V reference (±0.2% max at 25°C), and high-speed parallel interface supporting word/byte modes. It operates from a single 2.7 V to 5.25 V supply, consumes 3.6 mW at 3 V/625 kSPS, and supports software-configurable analog input types-including single-ended, pseudo-differential, and fully differential-enabling use in multichannel industrial data acquisition systems.

For engineers reviewing the AD7938BCP-6 datasheet, AD7938BCP-6 pinout, AD7938BCP-6 application, or AD7938BCP-6 equivalent, key selection considerations include its 69 dB SINAD at 50 kHz, no pipeline delay, VDRIVE-independent interface logic levels, ±1 LSB INL (differential mode), and 32-lead LFCSP package with exposed thermal pad.

Technical Context

The AD7938BCP-6 implements a SAR architecture with a wide-bandwidth differential track-and-hold amplifier capable of handling input frequencies up to 50 MHz. Its sequencer enables preprogrammed, automatic conversion across up to eight analog inputs without host intervention.

Conversion is triggered 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 supports flexible power management via control register bits, including autostandby (160 μA typ at 5 V) and full shutdown (2 μA max).

Key Specifications

Pinout & Package

AD7938BCP-6 is housed in a 32-lead, 5 mm × 5 mm LFCSP package (CP-32-7) with exposed thermal pad (EPAD) requiring connection to PCB ground plane via multiple vias for optimal thermal and noise performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7938BRUZ, the AD7938BCP-6 offers superior thermal performance and smaller footprint; compared with AD7934-6BCPZ, it provides double the channel count without increasing package size or power - making it optimal for dense, high-channel-count industrial DAQ.

Availability

AD7938BCP-6 is available at Aetrix Electronics and suitable for industrial process monitoring, motor drive current sensing, portable medical instrumentation, and test & measurement equipment requiring stable component supply, long-term obsolescence planning, and traceable sourcing.

Supply support for AD7938BCP-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 family was designed specifically for high-speed, multichannel data acquisition in space- and power-constrained industrial and instrumentation systems - emphasizing integration (on-chip sequencer, reference), flexibility (software-configurable inputs), and deterministic timing (no pipeline delay).

FAQ

What is the maximum analog input frequency supported by the AD7938BCP-6?

The AD7938BCP-6 features a wide-bandwidth track-and-hold amplifier rated for full-power bandwidth of 50 MHz (at 3 dB) and 10 MHz (at 0.1 dB). This allows accurate digitization of fast-rising signals and supports anti-aliasing filter design for input frequencies up to 50 MHz, though practical Nyquist-limited sampling rate remains 312.5 kHz at 625 kSPS. The AD7938BCP-6 maintains 69 dB SINAD at 50 kHz input frequency under differential mode conditions.

Does the AD7938BCP-6 require an external reference, or can it operate with its internal reference?

The AD7938BCP-6 can operate using its internal 2.5 V reference, specified at ±0.2% max accuracy at 25°C and 25 ppm/°C temperature coefficient. The VREFIN/VREFOUT pin provides this reference and may be overdriven with an external reference between 0.1 V and VDD. Using the internal reference eliminates external components and simplifies layout; external referencing is optional for applications demanding tighter initial accuracy or custom voltage scaling.

How does the sequencer function in the AD7938BCP-6, and how is it configured?

The AD7938BCP-6 sequencer automatically cycles through up to eight analog input channels based on settings in the control register's SEQ and address bits (ADD2–ADD0). It operates independently of the host processor once enabled, reducing firmware overhead. Configuration is performed by writing to the on-chip control register via the parallel interface (CS, RD, WR), with shadow register support for glitch-free updates. The sequencer supports both continuous and single-sequence modes.

What are the power management modes available on the AD7938BCP-6, and what are their typical current draws?

The AD7938BCP-6 offers Normal, Autostandby, and Full/Autoshutdown modes. In Normal mode, IDD is 1.5 mA max (5 V) or 1.2 mA max (3 V). Autostandby draws 160 μA typ at 5 V during low-throughput operation (e.g., 100 kSPS). Full/Autoshutdown draws ≤2 μA static current - ideal for sleep states. Power dissipation scales linearly with throughput, reaching 7.5 mW max at 5 V/625 kSPS and 3.6 mW max at 3 V/625 kSPS.

Can the AD7938BCP-6 interface directly with a 3.3 V microcontroller while operating from a 5 V analog supply?

Yes. The AD7938BCP-6 uses separate VDD (2.7–5.25 V analog supply) and VDRIVE (2.7–5.25 V digital I/O supply) pins. Setting VDRIVE = 3.3 V configures all parallel interface pins (DB0–DB11, CS, RD, WR, etc.) to 3.3 V logic levels - enabling direct, level-compatible connection to a 3.3 V microcontroller - while VDD remains at 5 V to optimize analog performance and SNR. VDRIVE must not exceed VDD by more than 0.3 V.