Analog Devices Inc. DC682A

Overview

DC682A from Analog Devices (formerly Linear Technology) is an evaluation board for the LTC1859 16-bit, 8-channel, 100ksps SoftSpan™ analog-to-digital converter. It enables rapid prototyping of high-accuracy data acquisition systems with software-programmable input ranges (±10V, ±5V, 0–10V, 0–5V), ±25V fault-protected inputs, and SPI/MICROWIRE™ serial interface. Designed for industrial process control and multiplexed DAQ applications requiring low INL (±3LSB) and 87dB SNR.

For engineers reviewing the DC682A datasheet, DC682A pinout, DC682A application, or DC682A equivalent, this page provides verified hardware configuration details, supported ADC variants (LTC1857/LTC1858/LTC1859), on-board reference calibration, jumper-selectable power domains (OVDD = 3V/5V), and layout-optimized signal routing for noise-sensitive 16-bit conversion.

Technical Context

The DC682A implements a complete signal chain for the LTC1859, including precision decoupling (1µF tantalum + 0.1µF ceramic on VREF; 10µF tantalum + 0.1µF ceramic on AVDD/DVDD/OVDD), buffered REFCOMP output (4.096V), and fault-protected analog input traces routed to screw terminals and header pins. It supports both single-ended and differential channel configurations via onboard jumpers and accommodates external reference injection at VREF.

All eight analog input channels (CH0–CH7) are brought out to 3.5mm screw terminals with 10kΩ series resistors and 3000pF NPO filtering capacitors per channel - matching Linear's recommended anti-aliasing design in Figure 2 of the LTC1859 datasheet. The board uses a 28-pin SSOP socket and includes CONVST, BUSY, RD, SCK, SDI, and SDO headers compatible with standard logic-level microcontrollers and FPGA development platforms.

Key Specifications

Availability

DC682A is available at Aetrix Electronics and suitable for industrial process control, multiplexed data acquisition systems, high-speed PC-based DAQ, and digital signal processing prototyping requiring stable component supply, traceable sourcing, and long-term lifecycle support.

Supply support for DC682A 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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.

The DC682A belongs to Analog Devices' legacy Linear Technology evaluation board family, specifically designed to accelerate validation and integration of precision multichannel ADCs like the LTC185x series into noise-sensitive, high-resolution measurement systems.

FAQ

What is the primary function of the DC682A evaluation board?

The DC682A evaluation board is a fully assembled and tested platform for evaluating the LTC1859 16-bit, 8-channel SoftSpan™ ADC - and its pin-compatible variants LTC1858 and LTC1857. It provides screw-terminal analog inputs, calibrated reference circuitry, SPI interface headers, and configurable power domains to enable immediate functional validation and system-level integration without custom PCB design. The DC682A allows engineers to verify timing, noise performance, range switching, and fault recovery behavior of the DC682A-hosted ADC under real-world conditions.

Does the DC682A support all three members of the LTC1857/LTC1858/LTC1859 family?

Yes, the DC682A supports all three devices via a single 28-pin SSOP socket. The board's passive components - including decoupling networks, reference bypassing, and input filtering - are designed to meet the worst-case requirements across the family (e.g., 16-bit resolution, ±3LSB INL, 87dB SNR). No hardware modification is needed to swap between LTC1857, LTC1858, or LTC1859; only firmware configuration changes are required to match resolution and timing parameters. The DC682A documentation explicitly lists compatibility with all three parts.

How is analog input protection implemented on the DC682A?

The DC682A implements ±25V overvoltage protection on all eight analog input channels (CH0–CH7) and the COM pin using the intrinsic clamping diodes of the LTC1859 IC, combined with 10kΩ series current-limiting resistors and 3000pF NPO ceramic filtering capacitors placed directly at each screw terminal. This matches Linear's recommended protection scheme in the LTC1859 datasheet (Figure 2) and ensures that fault conditions on unselected channels do not affect conversions on the selected channel - a core feature validated on the DC682A.

Can the DC682A operate with a 3.3V microcontroller interface?

Yes, the DC682A supports 3.3V digital interfacing via the OVDD power domain selector jumper. When configured for 3V operation, the digital output buffers (SDO, BUSY) are powered from 3V, ensuring safe voltage levels for connection to 3.3V logic families. All digital inputs (CONVST, RD, SCK, SDI) remain 5V-tolerant per the LTC1859 specification, so no level-shifting is required. This dual-voltage capability makes the DC682A compatible with modern low-voltage MCUs and FPGAs while retaining full functionality of the DC682A-hosted ADC.

Is external reference support available on the DC682A?

Yes, the DC682A provides direct access to the VREF pin (Pin 15) of the LTC1859 socket, allowing users to inject a precision external reference (e.g., LT6655, ADR45xx) to improve absolute accuracy beyond the internal 2.5V ±10ppm/°C reference. The onboard 1µF tantalum capacitor remains effective for external references with similar output impedance. When using an external reference, the internal VREF is disabled automatically - a behavior confirmed in the LTC1859 datasheet and validated on the DC682A hardware layout.