**AD670JN: A Comprehensive Technical Overview of the Precision 8-Bit ADC from Analog Devices**
The **AD670JN** from Analog Devices represents a significant milestone in the evolution of analog-to-digital converters, integrating a complete **8-bit ADC** with a precision voltage reference and a track/hold amplifier into a single 18-pin DIP package. This highly integrated design simplified system architecture for a wide range of data acquisition applications, establishing itself as a reliable workhorse for precision measurement.
At its core, the AD670JN is a successive-approximation register (SAR) ADC. This architecture strikes an excellent balance between speed, accuracy, and power consumption, making it suitable for many control and monitoring systems. The device features two pre-programmed, pin-selectable analog input ranges: **0 to +255mV** and **0 to +2.55V**. This flexibility allows it to interface directly with low-level transducers like thermocouples and load cells without requiring extensive external signal conditioning circuitry. The onboard **2.5V buried Zener reference** ensures stable and accurate conversion results across its operating temperature range.
A key advantage of the AD670JN is its **on-chip track/hold** amplifier. This circuit samples the analog input voltage and holds it constant during the conversion process, which is critical for achieving accurate digitization of dynamic signals. The converter communicates with a microprocessor via a simple 8-bit tri-state data bus, making interfacing straightforward. Conversion is initiated by a chip select (CS) signal, and the end of conversion (EOC) signal indicates when the data is ready to be read.
The performance of the AD670JN is characterized by several critical specifications. It offers a **typical conversion time of 10µs**, enabling a throughput rate of up to 100k samples per second. The device guarantees **no missing codes over the entire operating temperature range**, a fundamental specification for ADCs that ensures monotonicity. Its total unadjusted error is specified at ±½ LSB and ±1 LSB, highlighting its precision straight from the factory.
Typical applications for this converter were vast and included digital panel meters, process control systems, and medical instrumentation. Its ability to **interface directly with sensor outputs** and its simple microprocessor bus interface made it a versatile choice for engineers designing intelligent measurement systems in the industrial and scientific sectors.
**ICGOODFIND:** The AD670JN stands as a classic example of highly integrated mixed-signal design. It successfully combined essential signal chain components—a reference, track/hold, and ADC—into one robust package, significantly reducing design complexity and component count for precision 8-bit data acquisition systems.
**Keywords:** 8-Bit ADC, Successive Approximation, On-Chip Track/Hold, Buried Zener Reference, Data Acquisition
