Analog Devices Inc. AD7478AARMZ-REEL7

Overview

AD7478AARMZ-REEL7 from Analog Devices is an 8-bit, 1.2 MSPS successive-approximation ADC operating from a single 2.35 V to 5.25 V supply. It features 6-lead SC70 packaging, 7 ns minimum SCLK-to-data valid hold time at VDD > 3.6 V, and 225 ns track-and-hold acquisition time. It serves as a high-speed analog front-end in portable medical sensors requiring low-power, compact data acquisition.

For engineers reviewing the AD7478AARMZ-REEL7 datasheet, AD7478AARMZ-REEL7 pinout, AD7478AARMZ-REEL7 application, or AD7478AARMZ-REEL7 equivalent, key selection criteria include its 8-bit resolution with ±0.3 LSB INL/±0.3 LSB DNL, 12-cycle serial interface timing, 1 μA max standby current, and SC70 thermal impedance of 340.2°C/W - all critical for battery-powered signal chain design.

Technical Context

The AD7478AARMZ-REEL7 implements a standard SAR architecture with no pipeline delay, using CS falling edge to simultaneously sample VIN and initiate conversion. Its internal reference is derived from VDD, enabling a 0 V to VDD analog input range without external components.

Conversion timing is fully synchronous to SCLK: 12 cycles required at 20 MHz for full throughput (1.2 MSPS), with tQUIET ≥ 50 ns between conversions. The SDATA output provides four leading zeros followed by 8-bit MSB-first data and four trailing zeros, compatible with SPI/QSPI/MICROWIRE/DSP interfaces.

Key Specifications

Pinout & Package

AD7478AARMZ-REEL7 is housed in a 6-lead SC70 package (2.0 mm × 1.25 mm × 0.9 mm), optimized for space-constrained PCB layouts and thermally sensitive applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7822UID and MAX11100ETE+, AD7478AARMZ-REEL7 uniquely combines SC70 size, 5 V tolerance, VDD-referenced input scaling, and 1.2 MSPS throughput - making it optimal for compact, multi-rail portable instrumentation where layout area and supply flexibility are constrained.

Availability

AD7478AARMZ-REEL7 is available at Aetrix Electronics and suitable for portable medical devices, optical smoke detectors, industrial wireless sensor nodes, and smartphone ambient light sensing requiring stable component supply across automotive-grade temperature ranges (–40°C to +85°C).

Supply support for AD7478AARMZ-REEL7 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 AD7476A/AD7477A/AD7478A product line delivers ultra-compact, low-power SAR ADCs targeting space- and energy-constrained portable and battery-powered measurement systems.

FAQ

What is the maximum sampling rate supported by the AD7478AARMZ-REEL7?

The AD7478AARMZ-REEL7 supports a maximum throughput rate of 1.2 MSPS, achieved when using a 20 MHz SCLK and completing conversion in exactly 12 clock cycles. This rate is specified under conditions of VDD = 2.35 V to 5.25 V and TA = –40°C to +85°C. At lower SCLK frequencies, throughput scales linearly - for example, 10 MHz SCLK yields 600 kSPS. The AD7478AARMZ-REEL7 does not support oversampling or decimation modes.

Does the AD7478AARMZ-REEL7 require an external voltage reference?

No, the AD7478AARMZ-REEL7 uses an internal reference derived directly from VDD, establishing a full-scale input range of 0 V to VDD. This eliminates the need for external reference components and simplifies layout. The device does not support external reference injection; all conversions are inherently ratiometric to the supply rail, making it ideal for systems where sensor excitation and ADC reference share the same VDD source.

How is data formatted on the SDATA pin of the AD7478AARMZ-REEL7?

The AD7478AARMZ-REEL7 outputs a 12-bit frame on SDATA: four leading zeros, followed by the 8-bit conversion result (MSB first), followed by four trailing zeros. For example, a raw code of 0x7F appears as "0000_0111_1111_0000" across 12 SCLK falling edges. This fixed-length format ensures predictable timing and simplifies firmware parsing without bit-shift logic - a key advantage over variable-width protocols.

What is the thermal performance of the AD7478AARMZ-REEL7 in its SC70 package?

The AD7478AARMZ-REEL7 in SC70 has a junction-to-ambient thermal impedance (θJA) of 340.2°C/W and junction-to-case (θJC) of 228.9°C/W, per Analog Devices' Rev. G datasheet. Under typical 5.1 mW operation at 5 V, self-heating is limited to <1.8°C above ambient - well within specification limits. No heatsink or thermal pad is required, but PCB copper pour under the exposed pad (if present in variant) improves dissipation.

Can the AD7478AARMZ-REEL7 operate from a 2.0 V supply?

The AD7478AARMZ-REEL7 is specified for VDD = 2.35 V to 5.25 V. While the datasheet notes "operational from VDD = 2.0 V" for logic inputs (with VINH ≥ 1.8 V min), DC accuracy, dynamic performance, and guaranteed functionality are only validated down to 2.35 V. Using 2.0 V risks degraded SNR, increased INL, and potential failure to meet 1.2 MSPS timing - therefore, 2.35 V remains the absolute minimum recommended supply for reliable AD7478AARMZ-REEL7 operation.