Analog Devices Inc. AD7899BR-3

Overview

AD7899BR-3 from Analog Devices is a 14-bit, 400 kSPS successive-approximation ADC with ±2.5 V bipolar input range, internal 2.5 V reference, and single 5 V supply operation. It features 2.2 µs conversion time, 0.3 µs track/hold acquisition, and overvoltage protection up to ±18 V on analog inputs-used in precision industrial data acquisition systems requiring high DC accuracy and fast sampling.

For engineers reviewing the AD7899BR-3 datasheet, AD7899BR-3 pinout, AD7899BR-3 application, or AD7899BR-3 equivalent, key selection criteria include its ±1.5 LSB INL (B-grade), 77 dB SNR over temperature, two's complement output coding, and compatibility with both 3 V and 5 V digital interfaces via VDRIVE pin.

Technical Context

The AD7899BR-3 integrates a laser-trimmed internal clock oscillator (enabling 400 kSPS throughput without external timing components) and a high-input-impedance track/hold amplifier with 4.5 MHz –3 dB bandwidth. Its analog front-end supports only ±2.5 V full-scale range, with resistor-scaling network optimized for that range and two's complement output encoding.

Conversion control uses edge-triggered CONVST with BUSY/EOC dual-function status signaling; read access employs standard CS/RD strobes on a 14-bit parallel bus. Power management includes STBY pin enabling 20 µA standby current, and VDRIVE decoupling allows interoperability with 3 V logic families while maintaining 5 V analog supply integrity.

Key Specifications

Pinout & Package

AD7899BR-3 is housed in a 28-lead SOIC (R-28) package with standard 0.3-inch body width and 1.27 mm pitch. Pin 1 is marked by notch or dot; device orientation follows JEDEC MS-012.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 14-bit SAR ADC applications.

Compared with AD7899AR-3, the AD7899BR-3 provides tighter linearity for uncalibrated precision; compared with ADS8515IPW, it trades resolution for integration, reducing component count and simplifying timing design at the expense of ultimate DC accuracy.

Availability

AD7899BR-3 is available at Aetrix Electronics and suitable for industrial process monitoring, test equipment, motor drive current sensing, and medical instrumentation requiring stable component supply across extended temperature ranges.

Supply support for AD7899BR-3 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, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD7899 product line delivers high-speed, low-power, single-supply SAR ADCs with integrated references and flexible digital interfaces-designed specifically for space- and power-constrained industrial data acquisition systems.

FAQ

What is the input voltage range supported by the AD7899BR-3?

The AD7899BR-3 supports a fixed bipolar input range of ±2.5 V on the VINA pin, with VINB tied to AGND. This range is hardwired in the AD7899-3 variant and cannot be reconfigured for ±10 V, ±5 V, or unipolar modes. The ±2.5 V full-scale corresponds to a 5 V total span, yielding a 610.4 µV LSB step size. Overvoltage protection extends to –4 V to +18 V on VINA, safeguarding against field-induced transients.

Does the AD7899BR-3 require an external clock to operate at 400 kSPS?

No, the AD7899BR-3 does not require an external clock to achieve its rated 400 kSPS throughput. It contains an internal laser-trimmed oscillator that provides the necessary 6.5 MHz clock for 16-cycle conversions. An external clock may be applied via CLKIN only if custom timing or synchronization with other system clocks is needed; otherwise, tying CLKIN to GND enables default internal-clock operation.

How does the VDRIVE pin affect digital interface compatibility for the AD7899BR-3?

The VDRIVE pin on the AD7899BR-3 supplies power to all digital I/O buffers-including DB0–DB13, RD, CS, CONVST, BUSY/EOC, and STBY-allowing independent selection of 3 V or 5 V logic levels. When VDRIVE = 3 V, the AD7899BR-3 interfaces directly with 3 V microcontrollers without level shifters; when tied to VDD (5 V), it matches legacy 5 V systems. Input thresholds scale proportionally (VDRIVE/2 ± 0.4 V), ensuring reliable logic recognition across both voltages.

What is the significance of the "B" grade in AD7899BR-3?

The "B" in AD7899BR-3 denotes the B-grade temperature specification (–40°C to +85°C) and tighter DC accuracy: ±1.5 LSB maximum integral nonlinearity (INL) versus ±2 LSB for the A-grade AD7899AR-3. This improved linearity reduces system-level calibration burden in high-precision applications such as closed-loop motor control or calibrated test equipment where raw ADC accuracy directly impacts measurement confidence.

Can the internal 2.5 V reference of the AD7899BR-3 be used to drive external circuitry?

The internal 2.5 V reference is accessible at the VREF pin but is not intended to drive significant external loads. It has a nominal 6 kΩ output impedance due to an internal FET switch, limiting usable current to <100 µA without introducing measurable error. For driving external circuits (e.g., DAC references or sensor excitation), a low-impedance buffer amplifier or dedicated reference IC like the AD780 should be used; the AD7899BR-3 VREF pin serves primarily as a buffered reference source for its own ADC core.