AD7871KP

Overview

The AD7871KP is a complete monolithic 14-bit analog-to-digital converter (ADC) fabricated in LC2MOS technology. It integrates a track-and-hold amplifier, successive approximation ADC, and a 3 V buried Zener reference. The device operates from ±5 V power supplies with a typical power dissipation of 50 mW. It supports an input voltage range of ±3 V and achieves a throughput rate of 83 kSPS. Key electrical parameters include a signal-to-noise ratio of 80 dB at a 10 kHz input frequency, a maximum conversion time of 10.5 µs using the internal clock, and a data access time of 57 ns. The component is housed in a 28-pin PLCC package.

Feature Summary

• Integrates a laser-trimmed internal clock oscillator to eliminate external timing components.
• Provides versatile digital interface options including parallel, byte, and serial data formats.
• Features a self-contained architecture with an on-chip temperature-compensated reference.

Applications

• Digital signal processing
• High speed modems
• Speech recognition and synthesis
• Spectrum analysis
• DSP servo control

Procurement Notes

Verify the specific suffix 'K' against the manufacturer's ordering guide to confirm the commercial temperature range (0°C to +70°C). Ensure the package type matches the required footprint, as the AD7871 series includes multiple variants such as PDIP and CERDIP. Cross-reference the revision history for any updates to integral nonlinearity or SNR specifications before finalizing procurement.

Selection Notes

Select the AD7871 over the AD7872 when parallel or byte-mode data output is required, as the AD7872 is strictly serial. Consider the internal clock capability if system jitter must be minimized by overriding the on-chip oscillator. Verify that the ±3 V input range aligns with the application signal levels, noting that unipolar operation requires external circuit adjustments.

Part Context

The AD7871 belongs to a family of fast, complete 14-bit sampling ADCs designed for DSP users requiring dynamic performance specifications. It is manufactured using Analog Devices' LC2MOS mixed technology process. The device is distinct from the AD7872, which lacks parallel and byte output capabilities, offering only serial data transmission.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation.

FAQ

How is the data format selected on the AD7871?

The data format is controlled by the state of the 14/8/CLK pin. A logic high selects 14-bit parallel output, while a logic low or -5 V enables byte or serial data formats.

What is the function of the CONVST pin?

CONVST initiates the conversion process. A low-to-high transition places the track-and-hold into hold mode and starts the conversion sequence asynchronously to the clock.

Can the internal clock be overridden?

Yes, an external TTL-compatible clock may be applied to the CLK pin to synchronize ADC operation with the digital system for minimum noise.