Analog Devices Inc. AD7870AJNZ

Overview

AD7870AJNZ from Analog Devices is a complete monolithic 12-bit successive approximation analog-to-digital converter (ADC) with integrated track-and-hold amplifier, laser-trimmed internal clock, and on-chip 3 V buried Zener reference. It supports ±3 V bipolar input range, achieves 100 kHz sampling rate, delivers 70 dB SNR at 10 kHz input, and features 57 ns data access time. It is used in precision data acquisition systems requiring high dc accuracy and dynamic performance.

For engineers reviewing the AD7870AJNZ datasheet, AD7870AJNZ pinout, AD7870AJNZ application, or AD7870AJNZ equivalent, this page provides verified technical context, real-world interface timing constraints, confirmed package mapping to 24-pin DIP, and validated alternatives for industrial signal conditioning and DSP interfacing.

Technical Context

The AD7870AJNZ implements a SAR architecture with a fast-settling DAC, high-speed comparator, and internal 3 V temperature-compensated Zener reference. Its track-and-hold acquires signals to 12-bit accuracy in ≤2 μs, enabling full-power conversion up to 50 kHz while maintaining dc linearity (±1 LSB INL max) and dynamic fidelity (70 dB SNR).

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 accepts asynchronous CONVST or CS-triggered conversion, and internal clock operation (6.5–9 μs conversion) eliminates external timing components.

Key Specifications

Pinout & Package

AD7870AJNZ is housed in a 24-pin, 0.3-inch-wide plastic dual-in-line package (PDIP), compliant with JEDEC MS-001. Pin 1 is identified by a notch or dot; all pins are straight-leaded with 0.1 inch pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7870AJNZ, AD7871JNZ removes on-chip reference to reduce cost and power but increases system-level calibration complexity, while ADS7800KP trades integration for socket compatibility-neither offers the self-contained functionality or DIP footprint of AD7870AJNZ.

Availability

AD7870AJNZ is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, motor control, and medical signal conditioning requiring stable component supply across extended temperature ranges (−40°C to +85°C).

Supply support for AD7870AJNZ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7870AJNZ belongs to the LC2MOS 12-bit sampling ADC product line, designed specifically for precision data acquisition systems demanding integrated T/H, reference, and flexible digital interfacing in harsh industrial environments.

FAQ

What is the maximum analog input frequency supported by the AD7870AJNZ?

The AD7870AJNZ 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 acquisition time and 100 kHz sampling rate. The device's 0.1 dB bandwidth exceeds 500 kHz, ensuring minimal amplitude error and phase delay for signals within its Nyquist band. For optimal performance, input signals should remain below 50 kHz to avoid aliasing and preserve SNR.

Does the AD7870AJNZ require external clock components?

No, the AD7870AJNZ does not require external clock components. It integrates a laser-trimmed internal oscillator that guarantees conversion times of 6.5–9 μs. Connecting the CLK pin to VSS activates this internal clock. An external TTL-compatible clock (e.g., 2.5 MHz) may be applied to the CLK pin if precise timing synchronization or variable sampling rates are needed-but it is optional, not required.

How is the reference voltage used internally in the AD7870AJNZ?

The AD7870AJNZ uses its internal 3.00 V buried Zener reference for both the DAC core and the bipolar offset bias network. This single reference establishes the full-scale range (±3 V) and defines code transitions (1 LSB = 1.46 mV). The REF OUT pin provides access to this same reference for external circuitry, but loading must be limited to 500 μA and 50 pF to maintain accuracy and stability-exceeding these values degrades SNR and linearity.

Can the AD7870AJNZ interface directly with an 8-bit microcontroller bus?

Yes, the AD7870AJNZ supports direct 8-bit microcontroller interfacing via its byte-mode operation. When the 12/8/CLK pin is set to 0 V and HBEN is controlled appropriately, the device outputs two sequential 8-bit bytes (high byte first, then low byte) on DB7–DB0. This eliminates the need for external latches or data-width translators and is fully compatible with Intel 8051, Z80, and similar architectures.

What is the purpose of separate AGND and DGND pins on the AD7870AJNZ?

Separate AGND and DGND pins isolate analog and digital ground return paths to prevent noise coupling from digital switching transients into the sensitive analog front-end. AGND serves the track-and-hold amplifier, DAC, and reference; DGND serves logic outputs and control inputs. They must be connected at a single point-typically at the power supply star ground-to maintain signal integrity while avoiding ground loops. Improper grounding causes increased noise and degraded SNR in the AD7870AJNZ.