Analog Devices Inc. AD7896BR

Overview

AD7896BR from Analog Devices is a single-supply, 12-bit successive-approximation ADC with 8 µs conversion time, integrated track-and-hold amplifier and on-chip clock, operating from 2.7 V to 5.5 V and delivering 100 kHz throughput in high-sampling mode. It uses VDD as its reference, accepts 0 V to VDD analog input, and targets space-constrained data acquisition systems requiring low power and serial interface simplicity.

For engineers reviewing the AD7896BR datasheet, AD7896BR pinout, AD7896BR application, or AD7896BR equivalent, key selection considerations include its 2-wire serial interface timing (SCLK up to 10 MHz), automatic power-down behavior, unipolar input range tied to supply voltage, and SOIC-8 packaging for compact PCB layout.

Technical Context

The AD7896BR implements an R-2R ladder-based SAR architecture with laser-trimmed internal clock generation and a monolithic track-and-hold amplifier optimized for ≤1.5 µs acquisition to 12-bit accuracy. Its serial interface outputs 16-bit frames (4 leading zeros + 12-bit straight binary) synchronized to SCLK falling edges, with guaranteed data hold (10 ns) and access (60–110 ns) windows dependent on VDD.

It supports two distinct operating modes: Mode 1 (high-performance, 8 µs conversion, BUSY-driven timing) and Mode 2 (auto-sleep, 14 µs total cycle including 6 µs wake-up, ideal for intermittent sampling). Both modes rely on edge-triggered CONVST and BUSY status signaling, with no external reference or timing components required.

Key Specifications

Pinout & Package

AD7896BR is housed in an 8-lead SOIC package (width: 3.9 mm, body size: 4.9 mm × 6.0 mm), RoHS-compliant and rated for commercial temperature range (0°C to +70°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7822U and MAX1113ECM+, the AD7896BR uniquely combines VDD-referenced operation, integrated track-and-hold, BUSY signaling, and dual-mode power control in an SOIC-8 package-making it optimal for designs prioritizing component count reduction and mixed-voltage flexibility without sacrificing throughput or accuracy.

Availability

AD7896BR is available at Aetrix Electronics and suitable for industrial process monitoring, portable medical instrumentation, automated test equipment, smart building sensor nodes, and battery-powered data loggers requiring stable component supply and long-term obsolescence management.

Supply support for AD7896BR 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 AD7896BR belongs to Analog Devices' legacy precision ADC product line, designed specifically for space- and power-constrained applications demanding self-contained, easy-to-integrate analog-to-digital conversion without external support components.

FAQ

What is the maximum SCLK frequency supported by the AD7896BR?

The AD7896BR supports up to 10 MHz SCLK when operated at VDD = 5 V ±10%. At VDD = 2.7 V to 3.6 V, the maximum SCLK is limited by data access time (t4), requiring derating to ~6.5 MHz to meet timing margins. The part's t4 specification (60–110 ns) and t5 (10 ns) define the valid data window relative to SCLK falling edges-designers must verify setup/hold against their controller's timing budget. Exceeding these limits risks read corruption, especially during Mode 1 high-throughput operation.

Does the AD7896BR require an external voltage reference?

No, the AD7896BR does not require an external voltage reference. It uses VDD as its internal reference, enabling a true single-supply configuration with analog input range of 0 V to VDD. This eliminates the need for precision reference ICs, associated decoupling, and layout isolation-reducing BOM cost and PCB area. However, VDD regulation stability directly impacts full-scale accuracy: ±1% VDD variation introduces ±1% full-scale error, so low-noise, well-decoupled supplies are recommended for metrology-grade applications.

How does the AD7896BR enter and exit power-down mode?

The AD7896BR enters power-down mode automatically in Mode 2 when CONVST remains low after BUSY goes low (end of conversion). It exits power-down on the rising edge of CONVST, initiating a 6 µs wake-up period before track-and-hold enters hold mode. During wake-up, the part draws ~50 µA (VDD = 5 V) before resuming full operation. This behavior is confirmed in the Timing Characteristics table and Figure 3 of the AD7896BR datasheet-no software command or register write is needed, making it transparent to firmware.

What is the function of the BUSY pin on the AD7896BR?

The BUSY pin on the AD7896BR is an active-high, open-drain status indicator that asserts high on the falling edge of CONVST and returns low when conversion completes (after 8 µs in Mode 1 or 14 µs in Mode 2). It provides hardware synchronization for microcontrollers or FPGAs to avoid polling or fixed delays-enabling deterministic read timing. The pin's low-voltage specification (VOL ≤ 0.4 V at 1.6 mA sink) ensures compatibility with 3.3 V and 5 V logic families when pulled up externally.

Can the AD7896BR interface directly with a standard SPI peripheral?

The AD7896BR cannot interface directly with a standard SPI peripheral without firmware adaptation. Its 2-wire serial protocol uses SCLK and SDATA only-lacking dedicated CS, MOSI, or MISO lines-and requires precise timing around CONVST and BUSY. While the data format (16-bit MSB-first, 4-zero prefix) resembles SPI, the absence of chip select means the host must manage frame boundaries via CONVST edge detection and BUSY polling. Successful integration has been documented with ARM Cortex-M MCUs using bit-banged GPIO or custom SPI DMA configurations that respect the 400 ns inter-conversion guard band.