AD7870JN

Overview

The AD7870JN is a monolithic 12-bit successive approximation analog-to-digital converter (ADC) from Analog Devices. It integrates a track-and-hold amplifier, an 8 μs ADC core, and a laser-trimmed internal clock. The device operates on ±5 V power supplies with a typical power dissipation of 60 mW. It features a single-ended analog input range of ±3 V and provides parallel, byte, or serial digital output interfaces. Key performance metrics include a signal-to-noise ratio of 70 dB at a 10 kHz input frequency, a data access time of 57 ns, and integral nonlinearity of ±1/2 LSB typical. The component is housed in a 24-pin dual-in-line package.

Feature Summary

• Complete monolithic integration of a 12-bit SAR ADC, track-and-hold amplifier, and internal reference.
• Versatile digital interface supporting parallel, byte, and serial data output formats.
• Laser-trimmed internal clock oscillator eliminates the need for external timing components.
• Fast microprocessor interfacing with 57 ns data access time.

Applications

• Digital signal processing systems requiring high-speed sampling.
• Portable battery-powered instrumentation due to low power consumption.
• Industrial control systems utilizing standard microprocessors.
• Data acquisition systems needing integrated reference and timing.

Procurement Notes

Verify the specific temperature grade suffix (e.g., J for commercial, K/A for industrial) when ordering, as it dictates the operating range. Confirm the package type matches the design requirements, as the AD7870 series includes DIP, PLCC, and SOIC variants. Ensure supply voltages are strictly maintained within ±5% of nominal ±5 V to guarantee specified performance parameters.

Selection Notes

Select the AD7870JN for applications requiring a ±3 V input range and 12-bit resolution. Compare against AD7875 (0–5 V range) and AD7876 (±10 V range) if input voltage requirements differ. Consider the interface mode; the 12/8/CLK pin determines whether the device outputs 12-bit parallel, two 8-bit bytes, or serial data. Verify that the 57 ns access time meets the system's bus speed requirements.

Part Context

The AD7870 belongs to the LC2MOS family of complete 12-bit sampling ADCs. It shares architectural similarities with the AD7875 and AD7876, differing primarily in analog input voltage ranges. The J suffix denotes the commercial temperature grade variant packaged in a 24-pin plastic DIP. This part is designed for ease of use by integrating critical functions like clocking and referencing onto a single chip.

Replacement Considerations

The AD7870KNZ is a verified industrial-grade replacement offering the same electrical specifications but with an extended temperature range of -40°C to +85°C. Other variants such as the AD7870JPZ provide the same functionality in a PLCC package. Ensure pin compatibility and thermal requirements are met when substituting.