Analog Devices Inc. AD7938BCPZ-REEL7

Overview

AD7938BCPZ-REEL7 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 supports single-ended, pseudo-differential, and fully differential input configurations and operates from a single 2.7 V to 5.25 V supply. It is used in high-speed data acquisition systems requiring precise multi-channel sampling without pipeline delay.

For engineers reviewing the AD7938BCPZ-REEL7 datasheet, AD7938BCPZ-REEL7 pinout, AD7938BCPZ-REEL7 application, or AD7938BCPZ-REEL7 equivalent, key selection criteria include its 12-bit resolution, 1.5 MSPS throughput, software-configurable analog input modes, VDRIVE-enabled 3 V/5 V logic compatibility, and 32-lead LFCSP package with exposed thermal pad.

Technical Context

The AD7938BCPZ-REEL7 implements a SAR architecture with no pipeline latency, enabling deterministic conversion timing controlled by CONVST and CLKIN. Its track-and-hold amplifier supports full-power bandwidth up to 50 MHz and handles 50 kHz sinusoidal inputs with 69 dB SINAD in differential mode.

It integrates an on-chip sequencer for preprogrammed 8-channel conversion cycles, configurable via control register bits RANGE, CODING, and channel enable masks. The VDRIVE pin decouples digital I/O voltage (2.7 V–5.25 V) from analog supply (VDD), allowing direct interfacing with mixed-voltage microprocessors.

Key Specifications

Pinout & Package

The AD7938BCPZ-REEL7 is housed in a 32-lead Lead Frame Chip Scale Package (LFCSP), CP-32-7 variant, with an exposed thermal pad on the underside requiring connection to PCB ground plane via multiple vias.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7938BCPZ-REEL7, AD7939BCPZ-REEL7 trades 2 bits of resolution for lower cost and power, while AD7626BCPZ-REEL7 delivers 4 extra bits and 6.7× higher throughput at the expense of interface compatibility, reference dependency, and package size.

Availability

AD7938BCPZ-REEL7 is available at Aetrix Electronics and suitable for industrial process monitoring, medical instrumentation, automotive battery management, and test & measurement equipment requiring stable component supply and long-term production continuity.

Supply support for AD7938BCPZ-REEL7 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, with R&D and manufacturing operations worldwide.

The AD7938 is part of Analog Devices' precision SAR ADC product line, designed specifically for high-speed, multi-channel data acquisition in space- and power-constrained industrial and medical systems where deterministic timing and integrated functionality are critical.

FAQ

What is the maximum clock frequency supported by AD7938BCPZ-REEL7 for full 1.5 MSPS operation?

The AD7938BCPZ-REEL7 requires a CLKIN frequency of 25.5 MHz to achieve its rated 1.5 MSPS throughput. This is derived from its fixed 13-clock-cycle conversion time plus setup delay (t2). Operation at lower CLKIN frequencies reduces throughput proportionally, with minimum specified CLKIN at 700 kHz for basic functionality.

Does AD7938BCPZ-REEL7 support external reference inputs, and what is the valid voltage range?

Yes, AD7938BCPZ-REEL7 supports external reference inputs applied to the VREFIN/VREFOUT pin. The valid external reference range is 0.1 V to VDD. When using an external reference, the internal 2.5 V reference is disabled, and the analog input range scales accordingly (e.g., 0 to VREF for single-ended mode).

How does the VDRIVE pin affect the parallel interface behavior of AD7938BCPZ-REEL7?

The VDRIVE pin sets the logic threshold and output drive strength for all parallel data and control pins (DB0–DB11, RD, WR, CS, etc.). It may be supplied independently from VDD-enabling direct interfacing with 3 V or 5 V microprocessors even when VDD is 2.7 V or 5.25 V-as long as VDRIVE stays within −0.3 V to VDD + 0.3 V.

Can AD7938BCPZ-REEL7 perform conversions without a continuous master clock?

Yes, AD7938BCPZ-REEL7 accepts burst-mode CLKIN signals. The conversion process begins on the falling edge of CONVST and completes after exactly 13 CLKIN cycles (plus t2 setup time), so a continuous clock is not required-only sufficient edges during the active conversion window.

What is the purpose of the HBEN pin on AD7938BCPZ-REEL7, and how does it interact with the W/B pin?

HBEN (Pin 11) serves dual function: when W/B = high, it acts as DB8; when W/B = low, it becomes High-Byte Enable. In byte mode (W/B = low), asserting HBEN high places the top 4 bits of the 12-bit result on DB0–DB3, while DB4–DB6 carry the channel address-enabling efficient channel-aware readback without additional register polling.