Analog Devices Inc. AD7478AAKS-500RL7

Overview

AD7478AAKS-500RL7 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-ideal for space-constrained battery-powered data acquisition.

For engineers reviewing the AD7478AAKS-500RL7 datasheet, AD7478AAKS-500RL7 pinout, AD7478AAKS-500RL7 application, or AD7478AAKS-500RL7 equivalent, key selection criteria include its 12-cycle serial interface timing, 600 ns max conversion time, 1 μA standby current, SC70 thermal impedance (340.2°C/W), and guaranteed no-missed-codes performance across –40°C to +85°C.

Technical Context

The AD7478AAKS-500RL7 implements a standard SAR architecture with track-and-hold acquisition time of 225 ns max and aperture jitter of 30 ps typ. Conversion is initiated on the falling edge of CS and clocked by SCLK, requiring exactly 12 SCLK cycles for full 8-bit result output with four leading zeros followed by eight data bits MSB first.

It uses VDD as the reference source, eliminating external reference components and enabling rail-to-rail input (0 V to VDD). The device supports SPI/QSPI/MICROWIRE/DSP-compatible serial interfaces and enters full power-down mode with ≤1 μA quiescent current, activated via CS deassertion.

Key Specifications

Pinout & Package

AD7478AAKS-500RL7 is housed in a 6-lead SC70 package (2.0 mm × 1.25 mm × 0.9 mm), optimized for high-density PCB layouts and low thermal resistance (θJA = 340.2°C/W).

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, AD7478AAKS-500RL7 uniquely combines SC70-6 size, 1.2 MSPS throughput, and VDD-referenced operation-enabling smaller, faster, and simpler analog front-ends without sacrificing production-grade temperature range or reliability.

Availability

AD7478AAKS-500RL7 is available at Aetrix Electronics and suitable for battery-powered systems, portable medical instruments, optical sensor interfaces, and industrial control signal conditioning requiring stable component supply across automotive-qualified temperature ranges.

Supply support for AD7478AAKS-500RL7 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 AD747x family-including AD7478AAKS-500RL7-is designed for ultra-compact, low-power data acquisition in portable and energy-sensitive systems, emphasizing minimal external components and seamless microprocessor integration.

FAQ

What is the maximum sample rate supported by the AD7478AAKS-500RL7?

The AD7478AAKS-500RL7 supports a maximum throughput rate of 1.2 MSPS, achieved with a 20 MHz SCLK and 12-cycle serial interface. This corresponds to a minimum conversion period of 833 ns, including acquisition time. At lower SCLK frequencies, throughput scales linearly-e.g., 10 MHz SCLK yields ~600 kSPS. The device guarantees timing compliance across its full –40°C to +85°C operating range.

Does the AD7478AAKS-500RL7 require an external voltage reference?

No, the AD7478AAKS-500RL7 uses an internal reference derived from VDD, establishing a 0 V to VDD analog input range. This eliminates the need for external reference ICs, reducing BOM cost, PCB area, and potential drift sources. The reference accuracy is inherently tied to VDD stability, so proper supply regulation and decoupling remain essential for optimal INL and gain error performance.

How is data formatted on the SDATA pin of the AD7478AAKS-500RL7?

The AD7478AAKS-500RL7 outputs a 12-bit serial frame on SDATA: four leading zeros, followed by eight data bits (MSB first), followed by four trailing zeros. This fixed-length format ensures consistent timing and simplifies MCU firmware parsing. Data is clocked out on the falling edge of SCLK, and the output enters high-impedance state 36 ns after the final SCLK falling edge, allowing bus sharing.

What is the purpose of the CS pin on the AD7478AAKS-500RL7?

The CS (chip select) pin on the AD7478AAKS-500RL7 serves two critical functions: it initiates conversion on its falling edge and frames the serial data transfer. Sampling begins at the CS falling edge, and the subsequent SCLK pulses shift out the result. Holding CS low during multiple conversions enables continuous sampling mode. Deasserting CS places the device into full power-down mode, drawing ≤1 μA-making it ideal for duty-cycled sensing applications.

Can the AD7478AAKS-500RL7 operate from a 2.5 V supply?

Yes, the AD7478AAKS-500RL7 is fully specified for operation from 2.35 V to 5.25 V, including 2.5 V. At 2.5 V, it maintains 49 dB SINAD at 100 kHz, 1.2 MSPS throughput, and 1 μA standby current. Logic thresholds scale with VDD: VINH ≥ 1.8 V and VINL ≤ 0.4 V at 2.5 V, ensuring compatibility with common 2.5 V logic families. Power dissipation drops to ~3.2 mW at 1 MSPS, enhancing battery efficiency.