AD7878KN

Overview

The AD7878KN is a complete 12-bit analog-to-digital converter featuring an integrated DSP interface with an 8-word FIFO memory. It operates on dual ±5 V supplies and accepts bipolar analog inputs within a ±3 V range. The device utilizes an internal 3 V reference and achieves a signal-to-noise ratio of 72 dB at a 10 kHz input frequency. Data access time is specified at 57 ns, supporting direct interfacing with high-speed processors. It functions within a commercial temperature range of 0°C to +70°C.

Feature Summary

• Integrated 8-word first-in, first-out memory reduces software overhead for servicing interrupts in digital signal processors.
• On-chip track/hold amplifier and 3 V zener reference provide a complete digitizing solution without external components.
• Versatile DSP interface logic allows direct connection to processors such as the ADSP-2100 and TMS320 series.

Applications

• Digital Signal Processing
• Speech Recognition and Synthesis
• Spectrum Analysis
• High Speed Modems
• DSP Servo Control

Procurement Notes

Verify the specific grade suffix against the ordering guide to confirm performance parameters. The KN designation indicates a 72 dB SNR and 57 ns access time. Confirm package availability as Analog Devices may ship ceramic or cerdip variants. Check for military processing requirements if /883B notation is needed.

Selection Notes

Select this component when a complete ADC with built-in FIFO buffering is required for DSP applications. Ensure the system supports dual ±5 V power rails and TTL-compatible logic levels. Verify that the 12-bit resolution and 100 kHz sampling rate meet the dynamic performance needs of the target application.

Part Context

The AD7878 belongs to Analog Devices' LC2MOS family of high-speed data converters. This technology combines precision bipolar circuits with low-power CMOS logic. The part is designed to minimize software overhead in digital signal processing systems through its integrated memory and control logic.

Replacement Considerations

Public confirmed substitutes include AD7878JN, AD7878LN, and AD7878KP. Verify pin compatibility and electrical specifications before substitution.

FAQ

How does the AD7878 handle bus activity during conversion?

The device uses a bit decision slippage mechanism. If read/write operations occur during critical timing windows, the internal comparator strobe is deferred by one clock cycle to prevent spurious transients from affecting the conversion result.

What is the function of the ADD0 pin?

The ADD0 pin determines whether a read operation accesses the data word from the FIFO memory (logic low) or the contents of the status/control register (logic high).

Can the AD7878 operate with a single supply voltage?

No, the AD7878 requires dual supplies: VDD at +5 V and VSS at -5 V for specified performance.