Analog Devices Inc. AD7876CN

Overview

AD7876CN from Analog Devices is a complete monolithic 12-bit successive approximation ADC with integrated track-and-hold amplifier, laser-trimmed internal clock, and on-chip 3 V buried Zener reference. It supports ±10 V bipolar analog input range, achieves 100 kHz sampling rate, and delivers 57 ns parallel data access time. It is used in precision industrial data acquisition systems requiring high DC accuracy and stable full-scale performance across temperature.

For engineers reviewing the AD7876CN datasheet, AD7876CN pinout, AD7876CN application, or AD7876CN equivalent, this page provides verified technical context, confirmed pin functions, real-world interface timing constraints, and validated alternative options for ±10 V input-range 12-bit sampling ADCs in DIP/SOIC packages.

Technical Context

The AD7876CN implements a SAR architecture with internal 3 V reference routed to both DAC and bipolar bias circuitry, enabling direct ±10 V input scaling via on-chip resistor network (2.1R/7R/3R). Its track-and-hold acquires signals to 12-bit accuracy in ≤2 μs, and conversion completes in 6.5–9 μs using internal clock or 8 μs with 2.5 MHz external clock.

It supports three digital output formats-12-bit parallel, two-byte, and serial-via configurable 12/8/CLK pin and HBEN-controlled data bus mapping. BUSY/INT output provides asynchronous status signaling, while RD, CS, and CONVST enable flexible microprocessor or standalone control modes without external timing components.

Key Specifications

Pinout & Package

AD7876CN is housed in a 24-pin, 0.3-inch-wide plastic dual-in-line package (PDIP), pin-compatible with AD7870/AD7875 in same package variant. Pin functions are electrically validated per Analog Devices Rev. C datasheet Figure 2 and Table 5.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7870KN and ADS7822U, the AD7876CN uniquely combines ±10 V direct input, integrated reference, parallel/byte/serial interface, and self-contained clock - making it the only drop-in solution for legacy industrial DIP-based systems requiring minimal redesign.

Availability

AD7876CN is available at Aetrix Electronics and suitable for industrial process monitoring, test equipment design, energy metering, and motor drive current sensing requiring stable component supply and long-term obsolescence management.

Supply support for AD7876CN 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The AD7876CN belongs to the LC2MOS Complete ADC family, designed specifically for industrial data acquisition systems requiring monolithic integration, wide input voltage ranges, and guaranteed DC accuracy without external trimming.

FAQ

What is the maximum analog input frequency supported by the AD7876CN?

The AD7876CN supports full-power analog input signals up to 50 kHz while maintaining 12-bit accuracy. This is determined by its 100 kHz sampling rate and 2 μs track-and-hold acquisition time, which ensures less than 1/2 LSB error for sinusoidal inputs within that bandwidth. The device's 0.1 dB cutoff at ~500 kHz further confirms sufficient analog front-end bandwidth for anti-alias filtering implementation.

Does the AD7876CN require external components to operate?

No, the AD7876CN is a complete ADC requiring only power supply decoupling capacitors. It integrates a 12-bit SAR core, 2 μs track-and-hold amplifier, laser-trimmed internal clock oscillator, and 3 V buried Zener reference. No external op-amps, clock crystals, DACs, or reference buffers are needed - unlike most competing ADCs that demand ≥5 support components for basic operation.

How does the AD7876CN achieve ±10 V input range with a 3 V internal reference?

The AD7876CN uses an on-chip resistor network (2.1R/7R/3R) to scale the internal 3 V reference, generating precise ±10 V full-scale compliance at VIN. This network is laser-trimmed during manufacturing and forms part of the analog input stage shown in Figure 9 of the datasheet. No external resistors or op-amps are required to realize the ±10 V range.

Can the AD7876CN interface directly with an 8-bit microprocessor bus?

Yes, the AD7876CN supports byte-mode operation via HBEN and 12/8/CLK pins. When 12/8/CLK is low and HBEN is toggled, DB[7:0] and DB[11:4] become time-multiplexed low/high byte outputs - enabling direct connection to 8-bit data buses without glue logic. This is fully documented in Table 6 and Mode 2 timing diagrams (Figure 16) of the AD7876CN datasheet.

What is the purpose of separate AGND and DGND pins on the AD7876CN?

AGND and DGND provide isolated return paths for analog and digital circuitry to prevent noise coupling. AGND connects to the track-and-hold amplifier, reference, and DAC; DGND serves digital outputs and logic. They must be connected at a single point (typically at power supply star ground) to avoid ground loops while maintaining >60 dB PSRR. This separation is critical to achieving specified 70+ dB SNR performance.