Analog Devices Inc. AD7895BR-2

Overview

AD7895BR-2 from Analog Devices is a 12-bit, single-supply successive-approximation ADC with 3.8 µs conversion time in SOIC-8 package, featuring on-chip track/hold amplifier, unipolar 0 V to +2.5 V input range, straight binary output coding, and high-speed serial interface. It targets precision data acquisition in industrial sensor interfaces and portable instrumentation.

For engineers reviewing the AD7895BR-2 datasheet, AD7895BR-2 pinout, AD7895BR-2 application, or AD7895BR-2 equivalent, key selection considerations include its 0–2.5 V unipolar input range, 20 mW max power dissipation at 5 V, ±1 LSB relative accuracy, 70 dB SNR at 50 kHz, and automatic power-down mode for low-power sampling.

Technical Context

The AD7895BR-2 implements a laser-trimmed internal clock driving a 12-bit R-2R ladder SAR core, with integrated track/hold amplifier optimized for ≤100 kHz analog input bandwidth. Its serial interface uses SCLK and SDATA lines with data valid on falling SCLK edges, delivering 16-bit frames (4 leading zeros + 12-bit result).

It operates in two modes: Mode 1 (high-speed, 3.8 µs conversion) and Mode 2 (auto-sleep, 9.8 µs total cycle including 6 µs wake-up), both supporting up to 15 MHz SCLK and requiring ≥300 ns hold time before next CONVST edge to maintain 12-bit accuracy.

Key Specifications

Pinout & Package

AD7895BR-2 is housed in an 8-pin SOIC (SO-8) package with 1.27 mm pitch, JEDEC MS-012AC compliant, rated for –40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7894ARZ-10 and ADS7822U, the AD7895BR-2 uniquely combines integrated track/hold, guaranteed unipolar 0–2.5 V operation, and 5 V single-supply compatibility in SO-8-making it optimal for cost-sensitive, space-constrained industrial sensor nodes where external THA or level-shifting is undesirable.

Availability

AD7895BR-2 is available at Aetrix Electronics and suitable for industrial process monitoring, portable medical instrumentation, automated test equipment, energy metering reference designs, and sensor signal conditioning requiring stable component supply and long-term obsolescence management.

Supply support for AD7895BR-2 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD7895BR-2 belongs to Analog Devices' legacy precision data acquisition portfolio, designed specifically for space-constrained, low-power, single-supply industrial and instrumentation applications requiring integrated track/hold and simple serial interfacing.

FAQ

What is the maximum SCLK frequency supported by the AD7895BR-2?

The AD7895BR-2 supports up to 15 MHz SCLK. This limit is constrained by timing parameter t4 (data access time ≤603 ns) and t5 (data hold time ≥10 ns). At 15 MHz, the serial read completes in ~1.1 µs, enabling full 192 kSPS throughput when combined with 3.8 µs conversion and proper inter-conversion timing margins. Exceeding 15 MHz risks setup/hold violations and invalid data capture.

Does the AD7895BR-2 require an external reference, and what are the specifications?

Yes, the AD7895BR-2 requires an external 2.5 V reference applied to the REF IN pin. The specification mandates 2.375 V to 2.625 V (±5%), ≤1 µA input current, and ≤10 pF input capacitance. Precision references such as the AD780 or AD680 are recommended to maintain the specified ±1 LSB relative accuracy and 70 dB SNR performance of the AD7895BR-2.

How does the power-down mode operate in the AD7895BR-2?

The AD7895BR-2 enters power-down mode automatically when CONVST remains low after conversion completes (i.e., BUSY goes low). In this state, IDD drops to ≤10 µA across temperature, reducing power dissipation to ≤25 µW. The part "wakes up" on the rising edge of the next CONVST pulse, with a 6 µs wake-up time before track/hold enters hold mode-total Mode 2 conversion time is 9.8 µs. This behavior is intrinsic to the AD7895BR-2 design and requires no configuration registers.

What is the purpose of the four leading zeros in the AD7895BR-2 serial output frame?

The AD7895BR-2 outputs a 16-bit serial frame consisting of four leading zeros followed by the 12-bit conversion result. This fixed-length framing ensures deterministic timing for microcontroller SPI peripherals or GPIO bit-banging routines. The zeros provide alignment headroom, allowing the same firmware routine to handle all AD7895 variants (e.g., AD7895-10, AD7895-3) without conditional bit-shift logic-simplifying software maintenance across product families that use the AD7895BR-2.

Can the AD7895BR-2 interface directly with a 3.3 V microcontroller SPI port?

No, the AD7895BR-2 is a 5 V-only device: VDD must be +5 V ±5%, and its digital outputs (SDATA, BUSY) swing from 0.4 V (low) to 4.0 V (high) under load-exceeding 3.3 V logic high thresholds but risking damage to 3.3 V inputs if directly connected. Level translation (e.g., TXB0104 or resistor-divider on SDATA/BUSY) is required. For native 3.3 V compatibility, consider alternatives like the ADS7822U instead of the AD7895BR-2.