Analog Devices Inc. AD628ARMZ

Overview

AD628ARMZ from Analog Devices is a precision programmable-gain difference amplifier optimized for high common-mode voltage signal conditioning in industrial measurement systems. It delivers gain range 0.1–100, ±120 V input common-mode range at ±15 V supply, 75 dB minimum CMRR (dc to 500 Hz), and operates across −40°C to +85°C. It is used to scale ±10 V or 4–20 mA sensor outputs into the input range of single-supply ADCs.

For engineers reviewing the AD628ARMZ datasheet, AD628ARMZ pinout, AD628ARMZ application, or AD628ARMZ equivalent, key selection criteria include its 0.1–100 programmable gain architecture, ±120 V common-mode tolerance, RTI offset ≤ ±1.5 mV, 75 dB CMRR at dc–500 Hz, and MSOP-8 package compatibility with space-constrained industrial front ends.

Technical Context

The AD628ARMZ integrates a fixed-gain (G = +0.1) differential amplifier stage followed by a user-configurable output amplifier (G_A2 = 1 + R_EXT1/R_EXT2). Its internal 10 kΩ precision resistor (±0.1% absolute) at Pin 4 (CFILT) enables low-pass filtering or attenuation without external gain-setting resistors on the input path.

Input pins (+IN, −IN) are adjacent to supply pins (+VS, −VS) to preserve impedance balance and maintain >70 dB CMRR over temperature (−40°C to +85°C). The VREF pin (Pin 3) sets output common-mode voltage independently, enabling bipolar-to-unipolar conversion for single-supply ADC interfacing.

Key Specifications

Pinout & Package

The AD628ARMZ is housed in an 8-lead MSOP package (3.0 mm × 3.0 mm, 0.65 mm pitch), optimized for compact industrial PCB layouts and thermal performance (θ_JA = 132.54°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar difference amplifier applications.

Compared with INA149IDR and AD8479ARZ, the AD628ARMZ uniquely combines programmable gain (0.1–100), ±120 V CMV tolerance, and VREF-controlled output offset - enabling single-component adaptation to diverse industrial signal ranges without redesign.

Availability

AD628ARMZ is available at Aetrix Electronics and suitable for high-voltage current sensing, PLC analog input conditioning, and 4–20 mA loop receiver designs requiring stable component supply and long-term industrial lifecycle support.

Supply support for AD628ARMZ 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 Wilmington, MA.

The AD628 belongs to Analog Devices' precision difference amplifier product line, engineered specifically for industrial signal conditioning where high common-mode rejection, wide input voltage range, and programmable gain are essential.

FAQ

What is the maximum common-mode input voltage supported by the AD628ARMZ?

The AD628ARMZ supports a maximum common-mode input voltage of ±120 V when operated with ±15 V supplies. This rating is validated per Absolute Maximum Ratings Table 3 and confirmed in Figure 15 of the Rev. G datasheet. At lower supply voltages (e.g., ±2.5 V), the usable common-mode range contracts - for example, to −12 V to +17 V with a 5 V single supply and VREF = 2.5 V. Always verify operating conditions against Table 1 and Figure 30/31.

How is gain programmed on the AD628ARMZ?

Gain on the AD628ARMZ is programmed using two external resistors (REXT1 and REXT2) connected to Pin 6 (RG) and Pin 4 (CFILT). The total system gain follows G_TOTAL = 0.1 × (1 + REXT1/REXT2), enabling precise values from 0.1 to 100. Table 5 in the Rev. G datasheet lists standard 1% resistor combinations for gains including 0.2, 1, 10, and 100. The internal 10 kΩ precision resistor eliminates input-stage gain-setting complexity.

Does the AD628ARMZ require external components for basic operation?

Yes - the AD628ARMZ requires at minimum two external resistors (REXT1 and REXT2) to set gain, plus decoupling capacitors on +VS and −VS pins. A capacitor on Pin 4 (CFILT) is optional but recommended for anti-aliasing. The VREF pin may be tied to ground, mid-supply, or a precision reference depending on output level requirements. No external input resistors are needed due to the integrated 11:1 attenuator and 10 kΩ feedback element.

Can the AD628ARMZ interface directly with a 3.3 V microcontroller ADC?

Yes - the AD628ARMZ can interface directly with a 3.3 V microcontroller ADC by configuring VREF (Pin 3) to 1.65 V and selecting appropriate REXT1/REXT2 to scale the input (e.g., ±5 V → 0–3.3 V). Table 6 in the Rev. G datasheet provides verified resistor and VREF combinations for 3 V supplies, including ±5 V and ±10 V inputs mapped to 1.25 V mid-scale. Output swing remains within 0.9 V to 2.4 V under these conditions.

What is the purpose of the CFILT pin on the AD628ARMZ?

The CFILT pin (Pin 4) provides access to the internal 10 kΩ precision resistor connected to the noninverting input of the output amplifier. It enables three design functions: (1) adding a capacitor for low-pass filtering, (2) adding a series resistor to further attenuate the signal before the output stage, or (3) connecting a clamp circuit to limit output swing. This pin eliminates the need for external gain-setting resistors on the high-impedance input side, preserving CMRR and simplifying layout.