Analog Devices Inc. AD7678ACPRL

Overview

AD7678ACPRL from Analog Devices is an 18-bit, 100 kSPS charge redistribution SAR analog-to-digital converter with ±2.5 LSB INL, differential ±V_REF input (up to 5 V), and single 5 V supply operation. It delivers 103 dB dynamic range and 100 dB S/(N+D) at 2 kHz, targeting high-precision data acquisition in medical CT scanners and geophone sensor systems.

For engineers reviewing the AD7678ACPRL datasheet, AD7678ACPRL pinout, AD7678ACPRL application, or AD7678ACPRL equivalent, this page provides verified specifications, interface mode behavior, reference buffer operation, power dissipation profiles at 1 kSPS vs. 100 kSPS, and real-world timing constraints for parallel/serial read cycles.

Technical Context

The AD7678ACPRL implements a fully differential SAR architecture with no pipeline delay, enabling immediate result availability after conversion. Its internal conversion clock, on-chip error correction, and dual-mode digital interface (18-/16-/8-bit parallel or SPI/QSPI/MICROWIRE-compatible serial) support flexible system integration without external timing components.

It features an integrated reference buffer accepting 2.5 V on REFBUFIN to generate a stable 4.096 V output on REF, while supporting direct external reference use. Power management includes PDBUF control for buffer enable/disable and PD input for low-power shutdown, yielding 180 µW at 1 kSPS.

Key Specifications

Pinout & Package

AD7678ACPRL is available in a 48-lead LQFP package (CP-48-4 outline per Rev. B datasheet). The exposed pad is internally connected to AGND and should be soldered to system analog ground for mechanical reliability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-resolution SAR ADC applications.

Compared with AD7678ACPRL, AD7679ACPRL offers identical electrical performance in a thermally superior LFCSP package, while AD7674ACPRL lacks the integrated reference buffer and consumes more power - making AD7678ACPRL the optimal balance of feature set, power efficiency, and package flexibility.

Availability

AD7678ACPRL is available at Aetrix Electronics and suitable for CT scanner subsystems, geophone sensor interfaces, high-dynamic data acquisition modules, and Σ-Δ replacement designs requiring stable component supply and long-term manufacturability.

Supply support for AD7678ACPRL 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, serving precision instrumentation, industrial automation, and medical imaging markets.

The AD7678ACPRL belongs to the PulSAR® family of precision SAR ADCs, designed specifically for applications demanding 16–18-bit resolution, low power, and zero-latency conversion in harsh electromagnetic environments.

FAQ

What is the maximum recommended reference voltage for AD7678ACPRL?

The AD7678ACPRL supports an external reference voltage up to AVDD + 0.1 V, with AVDD nominally at 5 V - meaning REF may be as high as 5.1 V. However, the internal reference buffer is optimized for 4.096 V output when 2.5 V is applied to REFBUFIN, and full specified performance (including INL and dynamic range) is guaranteed only with V_REF = 4.096 V or 5 V. Using voltages outside this range may degrade AC accuracy metrics such as SFDR and THD.

Does AD7678ACPRL require an external reference, or can it operate with its internal buffer only?

The AD7678ACPRL can operate with its internal reference buffer enabled (PDBUF = LOW) by applying 2.5 V to REFBUFIN, which produces a stable 4.096 V on REF. No external reference IC is needed in this configuration. Alternatively, an external reference (e.g., ADR4540) may be connected directly to REF with PDBUF = HIGH. Both configurations are supported, but the internal buffer option reduces component count and improves thermal tracking between reference and analog front-end.

How does the MODE0/MODE1 pin configuration affect the AD7678ACPRL data bus behavior?

MODE0 and MODE1 pins configure the AD7678ACPRL's digital interface: MODE1=0/MODE0=0 selects 18-bit parallel mode (D[0:17] active); MODE1=0/MODE0=1 enables 16-bit high-word or low-word modes; MODE1=1/MODE0=0 configures byte-wide (8-bit) reads; MODE1=1/MODE0=1 activates serial mode (SDOUT/SCLK/SYNC). Pin states must be latched before CNVST assertion, and interface mode remains fixed until reset or power cycle - ensuring deterministic bus timing during continuous conversions.

What is the purpose of the BUSY signal on AD7678ACPRL, and how should it be used in system design?

The BUSY signal on AD7678ACPRL goes HIGH at conversion start and returns LOW upon data latching into the output register - indicating valid data is ready. It serves as a hardware-ready flag for microcontroller or FPGA interfaces, eliminating need for software polling. In parallel mode, BUSY's falling edge can directly clock a latch or trigger an interrupt; in serial mode, it synchronizes SDOUT read timing. Its 1.5 µs minimum HIGH width (t4) ensures reliable detection even with slow GPIOs.

Can AD7678ACPRL be powered down between conversions to reduce average power consumption?

Yes - the AD7678ACPRL supports power-down mode via the PD pin. When PD is driven HIGH after conversion completion, the device enters low-power state drawing only leakage current (not specified in datasheet but confirmed in functional description), reducing average power significantly in burst-mode applications. Recovery time from PD is not explicitly specified, but conversion can resume on next CNVST falling edge without reset. For lowest quiescent power, combine PD with PDBUF = HIGH and unused interface pins tied to valid logic levels.