Analog Devices Inc. AD7870LPZ

Overview

AD7870LPZ 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-enabling high-fidelity signal acquisition in data acquisition systems and DSP front-ends.

For engineers reviewing the AD7870LPZ datasheet, AD7870LPZ pinout, AD7870LPZ application, or AD7870LPZ equivalent, this page provides verified technical context, validated pin functions, confirmed dynamic and DC specifications, real-world interface timing constraints, and two rigorously cross-referenced alternative parts for system-level design continuity.

Technical Context

The AD7870LPZ implements a successive approximation register (SAR) architecture with an internal 3 V temperature-compensated buried Zener reference, enabling dc-accurate conversion without external trimming. Its track-and-hold acquires signals to 12-bit accuracy in ≤2 μs, supporting full-power input frequencies up to 50 kHz.

It supports three digital output formats-12-bit parallel, dual-byte, and serial-via configurable control pins (12/8/CLK, HBEN, SSTRB, SCLK, SDATA). Conversion is initiated either by CONVST rising edge or CS falling edge, with BUSY/INT providing status feedback and RD enabling synchronized data readout.

Key Specifications

Pinout & Package

AD7870LPZ is housed in a 24-pin, 0.3-inch-wide plastic DIP package (PDIP-24), with pin 1 identified by notch or dot. All pins are TTL-compatible for digital I/O and support standard logic level interfacing.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7870JRZ, AD7870LPZ provides through-hole assembly compatibility and identical analog performance; versus AD7871KPZ, it reduces component count and layout complexity by integrating reference and clock-making it optimal for cost-sensitive, medium-volume instrumentation designs.

Availability

AD7870LPZ is available at Aetrix Electronics and suitable for industrial data acquisition, test equipment, DSP interface, automated calibration, and embedded instrumentation requiring stable component supply and long-term obsolescence management.

Supply support for AD7870LPZ 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 AD7870LPZ belongs to the LC2MOS Complete ADC family-designed specifically for turnkey, high-accuracy data acquisition in industrial, instrumentation, and DSP-coupled systems where integration, stability, and ease of use are critical.

FAQ

What is the maximum analog input frequency supported by the AD7870LPZ while maintaining 12-bit accuracy?

The AD7870LPZ maintains full 12-bit accuracy for input signals up to 50 kHz. This is determined by its track-and-hold amplifier's 0.1 dB cutoff at ~500 kHz and guaranteed ≤2 μs acquisition time. At 100 kHz sampling, the Nyquist limit is 50 kHz-so the AD7870LPZ can digitize full-scale sine waves at that frequency with no missing codes and specified SNR/THD performance. Signals above 50 kHz require anti-alias filtering to prevent folding.

Does the AD7870LPZ require external clock circuitry to operate?

No, the AD7870LPZ does not require external clock circuitry. It features a laser-trimmed internal oscillator that guarantees conversion times of 6.5 μs (min) to 9 μs (max) without any external components. The CLK pin may be tied to VSS to enable the internal clock; alternatively, an external 2.5 MHz TTL clock may be applied for tighter timing control-but it is optional, not required.

How is the reference voltage generated and used internally in the AD7870LPZ?

The AD7870LPZ integrates a temperature-compensated buried Zener reference trimmed to 3.00 V ±10 mV. This reference serves dual roles: it sets the full-scale range for the internal 12-bit DAC and provides the dc bias for bipolar operation. The REF OUT pin makes this 3 V reference available externally (up to 500 μA load), but loading must remain constant during conversion to avoid gain error. For ±3 V input scaling, no external scaling is needed-the internal circuitry uses REF OUT directly.

Can the AD7870LPZ interface directly with a microcontroller lacking a 12-bit data bus?

Yes, the AD7870LPZ supports byte-mode and serial interfaces alongside 12-bit parallel. In byte mode (enabled by pulling 12/8/CLK low and controlling HBEN), it outputs upper and lower bytes on DB7–DB0. In serial mode (using SSTRB, SCLK, SDATA), it transmits 12-bit data LSB-first with framing-requiring only three GPIO lines. Both modes eliminate the need for a native 12-bit bus, making the AD7870LPZ compatible with 8-bit MCUs like the ATmega328P or ARM Cortex-M0+ devices.

What is the purpose of separating AGND and DGND pins on the AD7870LPZ, and how should they be connected?

AGND and DGND are separated to isolate analog signal paths from digital switching noise. AGND serves the track-and-hold, reference, and comparator; DGND serves digital I/O buffers and logic. They must be connected at a single point-typically at the star ground near the ADC's power supply decoupling capacitors-to prevent ground loops while maintaining low-impedance return paths. Splitting or routing them separately across the PCB introduces noise coupling that degrades SNR and INL.