AD7870LPZ

Overview

The AD7870LPZ is a monolithic 12-bit successive approximation analog-to-digital converter (ADC) from Analog Devices. It integrates a track-and-hold amplifier, an internal laser-trimmed clock, and a 3 V buried Zener reference. The device operates on ±5 V power supplies and accepts a bipolar analog input range of ±3 V. Key electrical specifications include a typical signal-to-noise ratio of 72 dB at a 10 kHz input frequency, a maximum conversion time of 8 μs with an external clock, and a data access time of 57 ns. Power dissipation is typically 60 mW. The component supports parallel, byte, and serial digital interfaces and is housed in a 24-pin dual-in-line package.

Feature Summary

• Complete monolithic integration of the ADC core, track-and-hold amplifier, and internal voltage reference.
• Versatile digital interface supporting parallel, byte, and serial data output formats for flexible microprocessor interfacing.
• Internal laser-trimmed clock oscillator eliminates the need for external timing components.
• Fast bus access times compatible with modern 8-bit and 16-bit microprocessors.

Applications

• Data acquisition systems requiring high-speed sampling
• Digital signal processing (DSP) front-ends
• Portable battery-powered instrumentation

Procurement Notes

Verify the specific temperature grade suffix (e.g., J, K, L) against the required operating range, as commercial grades differ from industrial variants. Confirm that the 24-pin DIP package aligns with the target PCB footprint. Ensure the ±5 V supply rails are stable within the specified tolerance to maintain accuracy. Check for moisture sensitivity levels if reflow soldering is planned.

Selection Notes

Select this component when a single-channel, 12-bit resolution is sufficient for the application. The AD7870 is appropriate for bipolar signals within the ±3 V range; use the AD7876 for ±10 V inputs or the AD7875 for unipolar 0 V to +5 V inputs. Consider the interface requirements, as the device supports multiple modes including serial communication which may reduce pin count in dense designs.

Part Context

The AD7870 belongs to the LC2MOS family of complete sampling ADCs, alongside the AD7875 and AD7876. These devices share a common architecture featuring a SAR core and integrated reference but differ in input voltage ranges and available packages. The LPZ suffix indicates a plastic leaded chip carrier variant, though standard documentation primarily references the 24-pin DIP for the AD7870 series.

Replacement Considerations

Direct functional replacements within the same family include the AD7875 and AD7876, provided the input voltage range matches the application needs. Verify pin compatibility and package dimensions before substitution, as the AD7876 utilizes a 24-pin SOIC package while the AD7870 uses a DIP.