Analog Devices Inc. AD7478AAKS-REEL

Overview

AD7478AAKS-REEL from Analog Devices is an 8-bit, 1.2 MSPS successive-approximation ADC in a 6-lead SC70 package, operating from 2.35 V to 5.25 V supply. It delivers 49 dB SINAD at 100 kHz input, features no pipeline delay, and uses internal VDD-referenced conversion for 0 V to VDD analog input range. It targets high-speed, low-power data acquisition in space-constrained portable systems.

For engineers reviewing the AD7478AAKS-REEL datasheet, AD7478AAKS-REEL pinout, AD7478AAKS-REEL application, or AD7478AAKS-REEL equivalent, key selection criteria include its 12 SCLK-cycle serial interface timing, 600 ns max conversion time, 1 μA standby current, SPI/QSPI/MICROWIRE/DSP compatibility, and guaranteed no-missed-codes performance across –40°C to +85°C.

Technical Context

The AD7478AAKS-REEL implements a standard successive-approximation register (SAR) architecture with a track-and-hold amplifier supporting >13 MHz full-power bandwidth. Conversion is initiated on the falling edge of CS, and sampling is precisely controlled by that same edge-eliminating pipeline latency.

It uses VDD as its reference source, enabling rail-to-rail analog input (0 V to VDD) without external components. Serial output is MSB-first, with four leading zeros followed by eight data bits and four trailing zeros, synchronized to the falling edge of SCLK.

Key Specifications

Pinout & Package

AD7478AAKS-REEL is housed in a 6-lead SC70 package (2.0 mm × 1.25 mm × 0.9 mm), optimized for ultra-compact 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 AD7478ARMZ and ADS7822U, the AD7478AAKS-REEL uniquely balances ultra-small SC70 packaging, 1.2 MSPS throughput, and sub-µA standby - making it optimal for miniaturized, battery-sensitive designs where every mm² and µA matters.

Availability

AD7478AAKS-REEL is available at Aetrix Electronics and suitable for portable medical sensors, battery-powered data loggers, optical sensor interfaces, and industrial edge node monitoring requiring stable component supply and long-term production continuity.

Supply support for AD7478AAKS-REEL 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 specifically to deliver high-speed, low-power SAR ADC performance in the smallest possible packages - targeting space- and energy-constrained portable and embedded systems.

FAQ

What is the maximum sampling rate supported by the AD7478AAKS-REEL?

The AD7478AAKS-REEL supports a maximum throughput rate of 1.2 MSPS, achieved when using a 20 MHz serial clock and operating within its specified supply (2.35 V to 5.25 V) and temperature (–40°C to +85°C) ranges. This rate corresponds to a minimum conversion time of 600 ns, defined by 12 SCLK cycles. At lower clock frequencies, throughput scales linearly - for example, 10 MHz SCLK yields ~1 MSPS.

Does the AD7478AAKS-REEL require an external voltage reference?

No, the AD7478AAKS-REEL 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, reduces BOM count and PCB area, and avoids reference-related drift or noise coupling - though system-level accuracy remains dependent on VDD stability.

How is data formatted on the SDATA pin of the AD7478AAKS-REEL?

The AD7478AAKS-REEL outputs data on the SDATA pin as a 12-bit serial frame: four leading zeros, followed by eight MSB-first conversion result bits, followed by four trailing zeros. The entire frame is clocked out on the falling edge of SCLK, beginning immediately after CS goes low. This fixed-length format simplifies host-side parsing and ensures deterministic timing regardless of input value.

What is the purpose of the CS pin on the AD7478AAKS-REEL beyond chip selection?

On the AD7478AAKS-REEL, the CS pin serves a dual role: it acts as both chip select and the precise sampling trigger. The falling edge of CS initiates the track-to-hold transition and starts the conversion process - defining the exact sampling instant. This eliminates aperture uncertainty from separate sample/convert control signals and ensures deterministic, single-cycle latency with no pipeline delay.

Can the AD7478AAKS-REEL operate from a 2.0 V supply?

The AD7478AAKS-REEL is specified to operate from 2.35 V to 5.25 V. While the datasheet notes operational capability down to 2.0 V for certain grades under specific logic-level conditions (e.g., VINH ≥ 1.8 V), this is not guaranteed across temperature or process variation. For reliable, production-ready operation across –40°C to +85°C, the 2.35 V minimum must be respected - using a 2.0 V supply risks timing violations, reduced SNR, or functional failure.