Analog Devices Inc. AD7870AJN

Overview

AD7870AJN from Analog Devices is a complete monolithic 12-bit sampling analog-to-digital converter (ADC) with integrated track-and-hold amplifier, laser-trimmed internal clock, and on-chip 3 V buried Zener reference. It delivers 100 kHz sampling rate, 72 dB SNR at 10 kHz input, ±3 V bipolar input range, and 57 ns data access time. It is used in precision data acquisition systems requiring high dynamic performance and microprocessor compatibility.

For engineers reviewing the AD7870AJN datasheet, AD7870AJN pinout, AD7870AJN application, or AD7870AJN equivalent, this page provides verified technical context, real-world interface timing constraints, confirmed package mapping to 24-pin DIP, and validated alternative options for industrial signal conditioning and DSP front-end designs.

Technical Context

The AD7870AJN implements a successive approximation register (SAR) architecture with a dedicated 2 μs track-and-hold amplifier and internal 3 V temperature-compensated Zener reference. Its conversion core operates with either internal laser-trimmed clock (6.5–9 μs) or external 2.5 MHz clock (8 μs), enabling deterministic timing without external timing components.

It supports three digital output formats-12-bit parallel, two-byte, and serial-via configurable pins (12/8/CLK, HBEN, SSTRB, SCLK, SDATA). Control logic responds asynchronously to CONVST rising edge or CS falling edge, and BUSY/INT provides status signaling for pipelined operation in real-time systems.

Key Specifications

Pinout & Package

AD7870AJN is housed in a 24-pin, 0.3 inch-wide plastic dual-in-line package (DIP), with pin 1 identified by notch or dot. The package meets JEDEC MS-001 standards and supports through-hole mounting with standard 0.1" pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit sampling ADC applications.

Compared with AD7870AJN, AD7875JN offers identical speed and noise performance but restricts input to unipolar ranges, while MAX195BCPP trades integrated reference and parallel interface for higher resolution and serial simplicity - neither is pin-compatible, but both serve overlapping data acquisition roles with distinct system trade-offs.

Availability

AD7870AJN is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, DSP-based control systems, and embedded sensor interface applications requiring stable component supply and long-term obsolescence management.

Supply support for AD7870AJN includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7870AJN belongs to the LC2MOS 12-bit sampling ADC product line, designed specifically for high-speed, high-accuracy data acquisition in industrial, instrumentation, and real-time control environments where integration, timing predictability, and dynamic performance are critical.

FAQ

What is the maximum analog input frequency supported by the AD7870AJN?

The AD7870AJN can accurately convert full-power analog signals up to 50 kHz while maintaining 12-bit accuracy. This is enabled by its 2 μs track-and-hold amplifier with >500 kHz 0.1 dB bandwidth. At 100 kHz sampling rate, the Nyquist limit is 50 kHz - matching the device's specified full-power bandwidth. Signals beyond this frequency will alias unless filtered externally.

Does the AD7870AJN require external components to operate?

No, the AD7870AJN is a complete ADC requiring only power supply decoupling capacitors (0.1 μF ceramic on VDD/VSS, 10 μF tantalum + 0.1 μF ceramic on REF OUT if used externally). It integrates a laser-trimmed clock, 3 V reference, track-and-hold amplifier, and interface logic - eliminating external timing crystals, reference ICs, or sample-hold circuits needed by discrete solutions.

How does the AD7870AJN handle bipolar offset and full-scale calibration?

The AD7870AJN supports external trim for bipolar zero error (±5 LSB max) and positive/negative full-scale error (±5 LSB max each), using dedicated adjustment pins per the datasheet's "Offset And Full-Scale Adjustment-AD7870" section. Calibration is performed with recommended 10-turn pots and must follow sequence: offset first, then full-scale. No internal auto-calibration is provided.

Can the AD7870AJN interface directly with an 8-bit microprocessor bus?

Yes, the AD7870AJN supports byte-mode operation via HBEN and 12/8/CLK pins, delivering upper and lower 8-bit bytes sequentially on DB7–DB0. With proper timing (t3 ≥ 60 ns RD pulse width, t6 ≤ 57 ns access time), it interfaces directly with 8085, Z80, or 6800-family processors without glue logic or latches.

What is the operating temperature range of the AD7870AJN?

The AD7870AJN is rated for commercial operation from 0°C to +70°C (J-grade). Its absolute maximum ratings extend to −55°C to +125°C, but guaranteed specifications - including SNR, INL, and conversion time - apply only within the 0°C to +70°C range. For extended temperature use, consider AD7870AN (−40°C to +85°C).