Analog Devices Inc. AD7894BRZ-3

Overview

AD7894BRZ-3 from Analog Devices is a 14-bit successive-approximation analog-to-digital converter (ADC) with ±2.5 V bipolar input range, 5 µs conversion time in high-speed mode, on-chip track/hold amplifier, and two-wire serial interface (SCLK/SDATA), designed for precision data acquisition in industrial instrumentation and sensor signal conditioning systems.

For engineers reviewing the AD7894BRZ-3 datasheet, AD7894BRZ-3 pinout, AD7894BRZ-3 application, or AD7894BRZ-3 equivalent, key selection considerations include its SO-8 package, ±2.5 V input scaling, twos-complement output coding, 77 dB SNR at 70 kHz, and automatic power-down mode enabling low-power operation in portable measurement equipment.

Technical Context

The AD7894BRZ-3 implements a laser-trimmed internal clock driving a 14-bit R-2R ladder SAR core, with integrated track/hold acquiring to ±1/2 LSB in ≤0.35 µs. Its analog front-end uses resistor-scaling networks (R1=R2=2 kΩ, R3 open) to support ±2.5 V full-scale input while operating from a single +5 V supply.

Timing is controlled via edge-triggered CONVST: falling edge initiates hold/conversion (BUSY high), and conversion completes in 5 µs (Mode 1) or 10 µs (Mode 2 with wake-up). Serial read requires 16 SCLK cycles (two leading zeros + 14 data bits), with data valid 10 ns after each SCLK falling edge and bus relinquish within 20 ns.

Key Specifications

Pinout & Package

AD7894BRZ-3 is housed in an 8-lead narrow-body SOIC (SO-8) package with standard JEDEC MS-012AC footprint (5.3 mm × 6.2 mm, 1.27 mm pitch). Pin 1 is marked by a beveled corner or dot; device orientation follows top-view pin numbering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7894ARZ-3, the AD7894BRZ-3 delivers tighter linearity for demanding sensor calibration tasks; versus ADS8325IPW, it trades resolution for integration, lower power, and simpler system design-making AD7894BRZ-3 optimal for compact, battery-aware 14-bit acquisition.

Availability

AD7894BRZ-3 is available at Aetrix Electronics and suitable for industrial process monitoring, portable test equipment, strain gauge data acquisition, and medical sensor interface applications requiring stable component supply across extended production lifecycles.

Supply support for AD7894BRZ-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, headquartered in Norwood, MA, with over 50 years of innovation in precision data conversion and signal conditioning.

The AD7894 product line was engineered for space-constrained, single-supply industrial and instrumentation systems requiring fast, accurate, and low-power analog-to-digital conversion without external support components.

FAQ

What is the maximum sampling rate achievable with the AD7894BRZ-3?

The AD7894BRZ-3 achieves a maximum throughput rate of 160 kHz in Mode 1 operation. This is calculated from its 5 µs conversion time, 1.0 µs serial read duration (at 16 MHz SCLK), and required 250 ns quiet time before the next CONVST edge. The timing constraint is governed by track/hold settling, not ADC core speed, ensuring full 14-bit accuracy at this rate.

Does the AD7894BRZ-3 require an external reference voltage?

Yes, the AD7894BRZ-3 requires an external +2.5 V reference applied to the REF IN pin. The device includes an on-chip buffer with ≤1 µA input current, making it compatible with precision references like the AD780 or AD680. Reference accuracy directly impacts gain error-±0.05% reference drift introduces ±0.05% full-scale error in the AD7894BRZ-3 output.

How does the automatic power-down mode function in the AD7894BRZ-3?

In automatic power-down mode (Mode 2), the AD7894BRZ-3 enters low-power sleep after conversion completes (BUSY goes low) if CONVST remains low. It wakes up internally ~5 µs before the next CONVST rising edge. This reduces average current to 20 µA max between conversions, cutting power consumption by >99% versus continuous operation-ideal for intermittent sampling in battery-powered AD7894BRZ-3 applications.

What is the purpose of the two leading zero bits in the AD7894BRZ-3 serial output?

The AD7894BRZ-3 outputs 16 serial bits per conversion: two leading zeros followed by 14 bits of twos-complement data. These zeros provide synchronization and framing-ensuring the 14-bit result aligns consistently in the MSB-aligned shift register of host microcontrollers. They also allow simple bit-shift discard in firmware, avoiding complex bit masking for the AD7894BRZ-3's native 14-bit word.

Can the AD7894BRZ-3 interface directly with a 3.3 V microcontroller?

Yes, but level-shifting is required on digital lines. The AD7894BRZ-3 operates at +5 V and specifies VIH ≥ 2.4 V and VIL ≤ 0.8 V, so its outputs (VOH ≥ 4.0 V, VOL ≤ 0.4 V) are 5 V-tolerant and can drive 3.3 V logic inputs safely. However, 3.3 V microcontroller SCLK must be translated to ≥2.4 V to meet AD7894BRZ-3's VIH requirement-using a simple resistor-divider or dedicated level shifter ensures reliable AD7894BRZ-3 communication.