Analog Devices Inc. AD677KR

Overview

AD677KR from Analog Devices is a 16-bit, 100 kSPS autocalibrating successive-approximation ADC with on-chip sample-hold, serial output, and ±VREF input range (±5 V to ±10 V). It delivers 90 dB S/(N+D), –99 dB THD, 1 MHz full-power bandwidth, and ±1.5 LSB INL over 0°C to +70°C - deployed in precision instrumentation and data acquisition systems requiring high dc accuracy and dynamic performance.

For engineers reviewing the AD677KR datasheet, AD677KR pinout, AD677KR application, or AD677KR equivalent, key selection considerations include its dual-chip BiMOS II/CMOS architecture, 28-lead SOIC package with separate analog/digital grounds and AGND sense, autocalibration timing (85,532 CLK cycles), and twos-complement serial interface synchronized to SCLK.

Technical Context

The AD677KR implements a switched-capacitor charge-redistribution SAR architecture with on-chip microcoded controller and calibration DAC. Its dual-die construction separates analog signal processing (BiMOS II) from digital control (DSP CMOS), minimizing crosstalk via isolated VCC/VEE/VDD supplies and dedicated AGND/DGND pins.

Autocalibration corrects capacitor-matching errors across the top nine bits using RAM-stored correction factors, enabling ±1.5 LSB INL without user trims. Conversion requires 17 CLK pulses per sample, with aperture jitter of 100 ps and input settling time of 2 µs - supporting accurate sampling of fast-slewing signals up to 1 MHz full-power bandwidth.

Key Specifications

Pinout & Package

AD677KR is housed in a 28-lead plastic SOIC (R-28) package with gull-wing leads, 0.050" pitch, and exposed pad not connected internally. Pin assignments are validated per Analog Devices AD677 datasheet Rev. A, Figure "SOIC Pinout".

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD7606BSTZ and ADS8588SIPM, the AD677KR provides superior dc accuracy (±1.5 LSB INL) and dynamic performance (90 dB S/(N+D), –99 dB THD) in a single-channel configuration, at the expense of channel count and integrated reference - making it optimal for metrology, calibration equipment, and high-end signal analysis where absolute linearity is non-negotiable.

Availability

AD677KR is available at Aetrix Electronics and suitable for high-accuracy data loggers, industrial process monitoring, and test & measurement equipment requiring stable component supply, long-term calibration traceability, and guaranteed commercial-temperature operation (0°C to +70°C).

Supply support for AD677KR 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 Wilmington, MA, with design centers worldwide.

The AD677KR belongs to Analog Devices' precision SAR ADC product line, engineered for applications demanding uncompromised dc accuracy, low distortion, and autonomous calibration - including metrology instruments, automated test equipment, and scientific data acquisition systems.

FAQ

What is the maximum recommended clock frequency for reliable operation of the AD677KR?

The AD677KR specifies a minimum CLK period of 480 ns (2.08 MHz), but Analog Devices recommends 580 ns (1.72 MHz) for optimal accuracy over temperature. Operation above this frequency may degrade INL and THD performance, especially under full-scale input conditions or across the full 0°C to +70°C range. The AD677KR datasheet confirms that 580 ns is not required during calibration cycles but is critical for production conversion accuracy.

Does the AD677KR require an external voltage reference, and what are the supported ranges?

Yes, the AD677KR requires an external voltage reference applied to the VREF pin. It supports 5 V to 10 V input ranges (±VREF), enabling full-scale input spans of ±5 V or ±10 V. Reference stability directly affects INL, THD, and S/(N+D) - the datasheet specifies performance metrics assuming a low-noise, well-decoupled 10.0 V reference. Using a 5 V reference reduces power consumption to 360 mW but slightly degrades dynamic specs.

How does the autocalibration function of the AD677KR impact system-level design?

The AD677KR autocalibration eliminates manual trimming and external calibration circuitry, reducing BOM count and board area. It executes in 85,532 CLK cycles (~40 ms at 2 MHz) and can be triggered at power-up or periodically. Because calibration stores correction factors in on-chip RAM, the AD677KR retains calibrated performance across sleep/wake cycles - crucial for battery-powered instrumentation where recalibration overhead must be minimized.

What is the purpose of the AGND SENSE pin on the AD677KR, and how should it be connected?

The AGND SENSE pin (Pin 15) provides remote sensing of the analog ground potential at the signal source, compensating for voltage drops across PCB traces or cables. It should be connected directly to the local ground of the sensor or signal-conditioning stage - not to the AD677KR's AGND pin - to enable accurate offset cancellation. This feature is essential when VIN originates meters away, such as in distributed sensor networks or chassis-grounded industrial sensors.

Can the AD677KR operate in continuous conversion mode, and what timing constraints apply?

Yes, the AD677KR supports continuous conversion mode by asserting SAMPLE HIGH before BUSY goes LOW - typically ~100 ns after the 17th CLK rising edge. This minimizes dead time between conversions and achieves maximum throughput. However, strict adherence to tFCD (50 ns min delay from SAMPLE fall to first CLK) and tSL (100 ns min SAMPLE low time) is mandatory; violating these risks incomplete sampling or corrupted output codes.