Analog Devices Inc. AD7875LP

Overview

AD7875LP 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 supports unipolar 0 V to +5 V analog input range, delivers 72 dB SNR at 10 kHz, achieves 8 μs conversion time with external 2.5 MHz clock, and operates from ±5 V supplies - enabling high-fidelity data acquisition in industrial instrumentation and DSP front-ends.

For engineers reviewing the AD7875LP datasheet, AD7875LP pinout, AD7875LP application, or AD7875LP equivalent, this page provides verified technical context, confirmed pin functions, real-world interface timing (57 ns data access), dynamic performance specs (SNR, THD), and validated alternatives for unipolar 12-bit sampling ADC replacement in embedded measurement systems.

Technical Context

The AD7875LP implements a successive approximation register (SAR) architecture with a dedicated 2 μs track-and-hold amplifier and internal 3 V reference, eliminating need for external precision references or timing components. Its conversion control is fully asynchronous via CONVST or CS edge-triggering, supporting standalone or microprocessor-synchronized operation.

It offers three configurable digital output formats - parallel 12-bit word, two 8-bit bytes, or serial data - each governed by the 12/8/CLK and HBEN pin states. The internal clock is laser-trimmed to guarantee 6.5–9 μs conversion time without external components, while external clock override remains supported for system-level synchronization.

Key Specifications

Pinout & Package

AD7875LP is housed in a 24-pin, 0.3-inch-wide plastic dual-in-line package (PDIP). Pin functions are electrically identical across AD7870/AD7875/AD7876 DIP variants per Analog Devices Rev. C datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7875LP, AD7870LP retains identical timing and packaging but mandates input signal conditioning for unipolar use, while ADS7822U reduces system integration but increases external component count and limits maximum sampling rate to 750 kSPS with higher noise floor.

Availability

AD7875LP is available at Aetrix Electronics and suitable for industrial data loggers, DSP-based signal analyzers, programmable logic controller (PLC) I/O modules, and medical patient monitoring front-ends requiring stable component supply across extended temperature ranges (−40°C to +85°C).

Supply support for AD7875LP 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, with over 50 years of innovation in precision data conversion and signal conditioning.

The AD787x family was designed specifically for high-speed, high-accuracy data acquisition in industrial automation and digital signal processing systems - emphasizing integrated functionality, guaranteed dynamic performance, and robust operation across military and extended temperature grades.

FAQ

What is the maximum sampling rate achievable with AD7875LP?

The AD7875LP supports a maximum sampling rate of 100 kHz, determined by its 8 μs conversion time with a 2.5 MHz external clock and 2 μs track-and-hold acquisition time. This allows full-power signal digitization up to 50 kHz (Nyquist limit), making AD7875LP suitable for audio-band and industrial vibration monitoring applications where phase coherence and amplitude fidelity are critical.

Does AD7875LP require external components to operate?

No, AD7875LP is a complete ADC subsystem requiring only decoupling capacitors on VDD, VSS, and REF OUT. It integrates a 3 V buried Zener reference, laser-trimmed clock oscillator, and 2 μs track-and-hold amplifier - eliminating external references, clock generators, and sample-hold circuits. External pull-up resistors (4.7 kΩ on SSTRB/SDATA, 2 kΩ on SCLK) are needed only for serial interface operation.

How does the 12/8/CLK pin configure AD7875LP interface modes?

The 12/8/CLK pin selects AD7875LP's digital interface: +5 V enables 12-bit parallel output only; 0 V enables byte or serial mode with gated SCLK; −5 V enables byte or serial mode with continuous SCLK. This single pin determines DB11/HBEN function, SCLK behavior, and data format - allowing hardware-selectable connectivity to 8-bit microcontrollers or serial DSP peripherals without firmware changes.

Can AD7875LP interface directly with a 3.3 V microcontroller?

AD7875LP digital outputs (VOH = 4.0 V min, VOL = 0.4 V max) are TTL-compatible and can drive 3.3 V logic inputs, but its digital inputs require VINH ≥ 2.4 V and VINL ≤ 0.8 V - compatible with 3.3 V CMOS levels. However, VDD/VSS must remain at ±5 V; level-shifting is unnecessary for signal integrity, though power supply isolation between ADC and MCU is recommended to maintain 72 dB SNR.

What is the purpose of separate AGND and DGND pins on AD7875LP?

AD7875LP uses separate AGND and DGND pins to isolate analog and digital return currents, preventing digital switching noise from modulating the analog input path and degrading SNR. These grounds must be connected at a single point - typically near the power supply entry - to maintain the specified 72 dB SNR and avoid ground loops that cause offset drift or harmonic distortion in precision measurements.