AD7875BQ

Overview

The AD7875BQ is a complete monolithic 12-bit successive approximation analog-to-digital converter (ADC) manufactured by Analog Devices. It integrates a track-and-hold amplifier, an 8 μs ADC core, and a laser-trimmed internal clock. The device operates from ±5 V power supplies and accepts a unipolar analog input range of 0 V to +5 V. It features a versatile digital interface supporting parallel, byte, and serial data output formats with a typical data access time of 57 ns. Key performance specifications include a signal-to-noise ratio of 72 dB at a 10 kHz input frequency and a maximum sampling rate of 100 kS/s. The component is housed in a hermetically sealed CDIP-24 package.

Feature Summary

• Integrates a 3 V buried Zener reference and laser-trimmed internal clock oscillator on a single chip.
• Supports flexible microprocessor interfacing through selectable parallel, byte, or serial data output modes.
• Features a high-speed track-and-hold amplifier capable of acquiring signals to 12-bit accuracy within 2 μs.

Applications

• Data acquisition systems requiring fast throughput and high linearity.
• Digital signal processing applications utilizing the specified dynamic performance parameters.
• Industrial control environments operating within extended temperature ranges.

Procurement Notes

Verify the specific suffix BQ indicates the military-grade temperature range and hermetic ceramic packaging configuration. Confirm that the ordering part number matches the required pinout and voltage specifications for the target application design. Ensure compatibility with existing system interfaces before finalizing procurement orders.

Selection Notes

Select the AD7875BQ when a unipolar 0 V to +5 V input range is required alongside high-speed conversion capabilities. Compare against the AD7870 and AD7876 if bipolar input ranges are necessary instead. Evaluate the integrated reference and clock features against designs requiring external timing components to determine cost and board space benefits.

Part Context

The AD7875BQ belongs to the AD7870/AD7875/AD7876 family of 12-bit sampling ADCs. While sharing identical architecture and interface logic, this specific model is distinguished by its unipolar input voltage range. The family provides options for various input spans and package types to suit different system requirements.

Replacement Considerations

The AD7875KNZ serves as a plastic leaded alternative within the same functional family. Verify package compatibility and thermal characteristics when substituting between hermetic and non-hermetic variants.

FAQ

How is the internal clock configured?

The internal laser-trimmed clock is enabled by tying the CLK pin to VSS. An external TTL-compatible clock may be applied to this pin to override the internal oscillator if required.

What is the function of the REF OUT pin?

The REF OUT pin provides the internal 3 V buried Zener reference voltage. It can supply up to 500 μA to an external load or be used to generate higher reference voltages via external scaling circuits.

How does the 12/8/CLK pin affect data output?

When held at +5 V, the device outputs a single 12-bit parallel word. When held at 0 V or −5 V, it enables byte or serial data formats, with the latter allowing continuous serial clocking at −5 V.