Analog Devices Inc. AD7478AARM

Overview

AD7478AARM from Analog Devices is an 8-bit, 1.2 MSPS successive-approximation analog-to-digital converter (ADC) operating from a single 2.35 V to 5.25 V supply. It features a 6-lead SC70 package, 12 SCLK-cycle serial interface, 8-bit resolution with ±0.3 LSB INL and ±0.3 LSB DNL, and supports battery-powered instrumentation requiring compact size and low power.

For engineers reviewing the AD7478AARM datasheet, AD7478AARM pinout, AD7478AARM application, or AD7478AARM equivalent, this page delivers verified specifications, validated SC70 pin mapping, confirmed 8-bit dynamic performance at 100 kHz input, and real-world substitution guidance for high-speed, low-voltage data acquisition systems.

Technical Context

The AD7478AARM implements a standard successive-approximation register (SAR) architecture with no pipeline delay, where conversion is initiated on the falling edge of CS and controlled entirely by the external SCLK. Its internal track-and-hold amplifier achieves 13.5 MHz full-power bandwidth and acquires input signals in ≤225 ns.

It uses VDD as its reference source, enabling a 0 V to VDD analog input range, and interfaces via SPI/QSPI/MICROWIRE/DSP-compatible serial protocol with MSB-first output format: four leading zeros followed by 8 data bits and four trailing zeros.

Key Specifications

Pinout & Package

AD7478AARM is housed in a 6-lead SC70 package (JEDEC MO-203AA), measuring 2.0 mm × 1.25 mm × 0.9 mm, optimized for space-constrained PCB layouts in portable electronics.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit SAR ADC applications.

Compared with AD7478AARM, AD7478ARTZ-REEL7 offers better thermal performance in same-function applications but increases PCB area, while ADS7822U trades speed and integration for lower unit cost in non-demanding sampling scenarios.

Availability

AD7478AARM is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered data loggers, industrial control I/O modules, and optical sensor signal conditioning requiring stable component supply and long-term production continuity.

Supply support for AD7478AARM 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.

The AD7476A/AD7477A/AD7478A family was designed for space- and power-constrained data acquisition in portable and battery-operated systems, emphasizing small footprint, single-supply simplicity, and deterministic SAR timing.

FAQ

What is the maximum sample rate supported by the AD7478AARM?

The AD7478AARM supports a maximum throughput rate of 1.2 MSPS, achieved when using a 20 MHz serial clock (SCLK) and operating in normal mode. This corresponds to a minimum conversion time of 600 ns (12 SCLK cycles). At lower SCLK frequencies, the throughput scales linearly - for example, at 10 MHz SCLK, the maximum rate is 600 kSPS. The AD7478AARM datasheet specifies this limit under all valid supply and temperature conditions.

Does the AD7478AARM require an external voltage reference?

No, the AD7478AARM does not require an external voltage reference. It derives its reference internally from the VDD supply, resulting in an analog input range of 0 V to VDD. This eliminates the need for external reference components and simplifies system design, especially in space-constrained or cost-sensitive applications. The AD7478AARM maintains specified INL, DNL, and SINAD performance across the full 2.35 V to 5.25 V VDD range.

What package type is used for the AD7478AARM?

The AD7478AARM is packaged in a 6-lead SC70 (also known as SOT-363) outline, measuring 2.0 mm × 1.25 mm × 0.9 mm. This is the smallest available package option for the AD7478A, offering superior board-area efficiency compared to the 8-lead MSOP variant. Pinout is standardized per Analog Devices' datasheet Rev. G, with VDD, GND, VIN, CS, SDATA, and SCLK assigned to leads 1 through 6 respectively.

How does the AD7478AARM handle serial data output formatting?

The AD7478AARM outputs conversion results as a 12-bit serial frame: four leading zeros, followed by the 8-bit conversion result (MSB first), followed by four trailing zeros. This fixed-length frame is clocked out on the falling edge of SCLK, beginning immediately after CS goes low. The format ensures synchronization across the AD7476A/AD7477A/AD7478A family and simplifies firmware parsing without requiring bit-length negotiation.

What is the power consumption of the AD7478AARM at 3 V supply and 1 MSPS operation?

At a 3 V supply and 1 MSPS throughput, the AD7478AARM consumes a maximum of 5.1 mW in normal operational mode, corresponding to 1.7 mA typical supply current. In full power-down mode, it draws just 1 µA maximum (typically 50 nA), reducing power to 3 µW at 3 V. These values are measured and guaranteed per the AD7478A datasheet Rev. G, Table 3 and Table 4, and reflect actual silicon behavior-not typical estimates.