In the realm of data acquisition and digital signal processing, the conversion of analog signals into precise digital codes is a fundamental operation. The **AD667KN** from Analog Devices stands as a significant milestone in the evolution of 12-bit analog-to-digital converters (ADCs), representing a blend of **robust performance, reliability, and historical engineering excellence**. This monolithic, complete ADC has been a workhorse in industrial, military, and communications systems for decades, cementing its status as a classic component.
At its core, the AD667KN is a complete 12-bit successive approximation register (SAR) ADC. Its "complete" moniker is well-earned; the chip integrates all essential components for the conversion process on a single die. This includes a **high-accuracy voltage reference, a precision bipolar sample-and-hold amplifier, and a clock oscillator**. This high level of integration drastically simplifies system design, reducing the need for numerous external components and thereby enhancing overall system reliability while minimizing board space.
A key feature of the AD667KN is its **impressive DC accuracy**. The converter boasts excellent linearity, with a maximum ±0.012% non-linearity error (or ±½ LSB), ensuring that the digital output is a faithful representation of the analog input across its entire dynamic range. This precision is critical for applications requiring exact measurements, such as precision instrumentation and automated test equipment (ATE). The internal buried Zener voltage reference provides a stable and low-drift 10.0V output, which is fundamental to maintaining this accuracy over time and temperature variations.
The device offers flexible input ranges, a major contributor to its versatility. Through simple pin strapping, the analog input can be configured for four bipolar ranges (±10V, ±5V, ±2.5V, ±1.25V) and four unipolar ranges (0 to +10V, 0 to +5V, 0 to +2.5V, 0 to +1.25V). This programmability allows a single ADC to interface with a wide array of sensors and signal conditioning circuits without requiring additional scaling hardware. The conversion speed, while not comparable to modern high-speed ADCs, is a respectable 100kSPS (kilo-samples per second), making it suitable for a vast number of process control and data logging applications where speed is secondary to accuracy.
Housed in a 32-pin DIP (Dual In-line Package), the AD667KN was designed for ease of use and integration into the systems of its era. Its interface is straightforward, utilizing standard control signals like CONVERT (or SC) and BUSY to manage the conversion cycle and read data. The output data is presented in a 12-bit parallel format, with three-state output buffers allowing for easy connection to microprocessor data buses.
Despite being a legacy component, the AD667KN's design principles continue to inform modern ADC development. Its **enduring legacy is a testament to its robust architecture and exceptional performance** in demanding environments. It exemplifies an era of analog design where precision, integration, and reliability were paramount.
**ICGOODFIND:** The AD667KN is a quintessential example of a high-performance, fully integrated 12-bit data acquisition solution. Its self-contained design, exceptional DC accuracy, and flexible input configuration made it an industry standard. For engineers designing or maintaining systems where utmost precision is required over extreme speed, the AD667KN remains a benchmark of reliability and analog engineering prowess.
**Keywords:** Analog-to-Digital Converter (ADC), 12-Bit Resolution, Successive Approximation Register (SAR), Data Acquisition, Voltage Reference.
