Analog Devices Inc. AD7451BRM

Overview

AD7451BRM from Analog Devices is a 12-bit, 1 MSPS pseudo-differential successive approximation register (SAR) analog-to-digital converter (ADC) operating from a single 2.7 V to 5.25 V supply. It features 70 dB SINAD at 100 kHz input, ±1 LSB INL (B version), 888 ns conversion time, and SPI-/QSPI-/MICROWIRE-compatible serial interface - used in portable instrumentation for high-fidelity sensor digitization.

For engineers reviewing the AD7451BRM datasheet, AD7451BRM pinout, AD7451BRM application, or AD7451BRM equivalent, key selection considerations include its 12-bit resolution with no pipeline delay, 8-lead SOT-23 package, 1 μA power-down current, pseudo-differential input architecture, and compatibility with microprocessor/DSP serial interfaces requiring minimal board space and low power.

Technical Context

The AD7451BRM implements a capacitive DAC-based SAR architecture with differential track-and-hold (T/H), enabling true 12-bit accuracy without latency or pipeline artifacts. Its conversion is initiated by CS falling edge and clocked entirely by SCLK - eliminating internal timing dependencies and allowing precise sampling control.

It supports external reference voltages from 100 mV to VDD, with specified performance at 2.5 V; the pseudo-differential input (VIN+, VIN–) uses VIN– as a programmable common-mode reference point rather than a true differential pair, simplifying transducer interfacing while retaining noise rejection benefits.

Key Specifications

Pinout & Package

AD7451BRM is housed in an 8-lead SOT-23 package (JEDEC MO-178AA), with 0.65 mm lead pitch and 2.9 mm × 1.6 mm footprint - optimized for space-constrained portable designs. Thermal impedance θ_JA = 211.5°C/W supports operation up to +85°C ambient without forced cooling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7451BRM, AD7450BRM trades 2 bits of resolution for lower cost and marginally lower power, while ADS7822U sacrifices speed and package size for TI's production support and alternate qualification - neither offers pin compatibility or identical 1 MSPS capability.

Availability

AD7451BRM is available at Aetrix Electronics and suitable for transducer interface, battery-powered systems, and portable instrumentation requiring stable component supply, long-term manufacturability, and guaranteed traceability.

Supply support for AD7451BRM 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, with design centers worldwide.

The AD7451BRM belongs to Analog Devices' precision SAR ADC product line, engineered for high-speed, low-power, and high-accuracy data acquisition in space- and energy-constrained applications.

FAQ

What is the maximum sampling rate supported by the AD7451BRM?

The AD7451BRM supports a maximum throughput rate of 1 MSPS under specified conditions: VDD = 2.7 V to 5.25 V, fSCLK = 18 MHz, and VREF = 2.5 V. This rate is achieved with a fixed 16 SCLK-cycle conversion time (888 ns), and the device maintains full 12-bit accuracy and 70 dB SINAD at this speed - making AD7451BRM suitable for demanding real-time signal capture applications.

Does the AD7451BRM require an external reference voltage?

Yes, the AD7451BRM requires an external reference voltage applied to the VREF pin. It accepts a reference from 100 mV to VDD, with 2.5 V being the specified nominal value for guaranteed performance. The reference directly sets the full-scale input range (VIN+ − VIN–), and must be decoupled with at least a 0.1 μF capacitor to GND. No internal reference is provided - AD7451BRM relies entirely on this external source for accuracy and stability.

What does "pseudo-differential input" mean for the AD7451BRM?

For the AD7451BRM, "pseudo-differential input" means VIN+ is the active analog input, while VIN– serves as a user-configurable common-mode reference point - not a true complementary input. VIN– can be tied to ground, a DC bias, or a low-impedance noise-rejecting node, allowing VIN+ to measure against that reference. This architecture provides common-mode noise rejection without requiring matched differential drivers, simplifying interface to single-ended sensors while retaining key benefits of differential signaling - a defining feature of AD7451BRM's system-level flexibility.

Is the AD7451BRM pin-compatible with the AD7441 series?

Yes, the AD7451BRM shares identical pin configuration, package (8-lead SOT-23), and electrical interface with the AD7441 series - including matching VDD, SCLK, SDATA, CS, VREF, VIN+, VIN–, and GND assignments. However, AD7441 is a 10-bit device with different timing (10-bit data format), lower SINAD (61 dB), and distinct DC specs (e.g., ±0.5 LSB INL). While PCB layout is interchangeable, firmware must handle differing data length and performance expectations - AD7451BRM is not a drop-in replacement without software adaptation.

What power supply voltage range is valid for the AD7451BRM?

The AD7451BRM operates from a single supply voltage ranging from 2.7 V to 5.25 V. Performance specifications - including 1 MSPS throughput, 70 dB SINAD, and ±1 LSB INL - are guaranteed across this full range. Power dissipation scales with VDD: 4 mW maximum at 3 V/1 MSPS versus 9.25 mW maximum at 5 V/1 MSPS. The supply must be decoupled with both 0.1 μF ceramic and 10 μF tantalum capacitors to GND to ensure stable ADC operation - a requirement explicitly defined for AD7451BRM in its datasheet.