Analog Devices Inc. AD7876BQ

Overview

AD7876BQ from Analog Devices is a complete monolithic 12-bit successive approximation ADC with integrated 3 V buried Zener reference, 2 μs track-and-hold amplifier, and laser-trimmed internal clock. It supports ±10 V bipolar input range, delivers 8 μs conversion time (internal clock), and features parallel/byte/serial digital interfaces. It is used in precision industrial data acquisition systems requiring high dc accuracy and stable full-scale performance.

For engineers reviewing the AD7876BQ datasheet, AD7876BQ pinout, AD7876BQ application, or AD7876BQ equivalent, this page provides verified technical context, real-world interface timing values, confirmed analog input scaling architecture, and validated alternative options for ±10 V-range 12-bit sampling ADCs in SOIC-24 packaging.

Technical Context

The AD7876BQ implements a SAR-based conversion architecture with on-chip 3 V temperature-compensated Zener reference, enabling direct ±10 V input scaling via internal resistor network (2.1R/7R/3R). Its track-and-hold acquires to 12-bit accuracy in ≤2 μs, and internal clock guarantees 6.5–9 μs conversion time without external timing components.

Digital interface flexibility includes Mode 1 (parallel 12-bit), Mode 2 (two-byte), and serial (SCLK/SSTRB/SDATA) formats, all controlled by the 12/8/CLK pin state. BUSY/INT output signals conversion completion asynchronously, while CONVST rising edge initiates hold mode independent of clock phase.

Key Specifications

Pinout & Package

AD7876BQ is housed in a 24-pin small outline integrated circuit (SOIC) package with standard 0.3-inch body width and 0.050-inch lead pitch. Pin 1 identifier is marked by a notch or dot; pins are numbered counterclockwise from top-left corner when viewed from top.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD7876BQ, AD7875BQ shares identical timing, packaging, and interface logic but cannot accept bipolar inputs; ADS8505IPW offers higher resolution and speed but requires external reference, additional decoupling, and SPI controller support - increasing firmware and layout complexity.

Availability

AD7876BQ is available at Aetrix Electronics and suitable for industrial process monitoring, test & measurement equipment, and energy metering systems requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for AD7876BQ 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 global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, founded in 1965 and headquartered in Wilmington, MA.

The AD787x family was designed specifically for high-accuracy, self-contained data acquisition in industrial and instrumentation applications where integration, dc precision, and ease of microprocessor interfacing are critical.

FAQ

What is the maximum analog input frequency supported by the AD7876BQ?

The AD7876BQ can accurately convert full-power analog signals up to 50 kHz. This is enabled by its 2 μs track-and-hold acquisition time and 100 kHz maximum sampling rate. The 0.1 dB bandwidth of the internal track-and-hold amplifier is typically 500 kHz, ensuring minimal settling error even at high input frequencies. For optimal SNR above 10 kHz, proper PCB layout with separate AGND/DGND planes and local decoupling is required. The AD7876BQ maintains 70 dB SNR at 10 kHz input under specified conditions.

Does the AD7876BQ require external components to operate?

No, the AD7876BQ is a complete monolithic ADC requiring only power supply decoupling capacitors for operation. It integrates a 3 V buried Zener reference, laser-trimmed internal clock oscillator, 2 μs track-and-hold amplifier, and 12-bit SAR core. External components are optional: 4.7 kΩ pull-up resistors on SSTRB/SDATA for serial mode, 2 kΩ pull-up on SCLK, and recommended RC decoupling (200 Ω + 10 μF tantalum || 0.1 μF ceramic) on REF OUT if used externally. No external DAC, op-amps, or timing crystals are needed.

How does the AD7876BQ handle ±10 V input scaling internally?

The AD7876BQ uses an internal resistor network (2.1R/7R/3R) to scale the ±10 V input down to match the 3 V internal reference range, producing a twos-complement 12-bit output where 1 LSB = 4.88 mV. This scaling is implemented within the track-and-hold stage and requires no external components. The analog input impedance is typically 33 kΩ. Unlike the AD7870 (±3 V) or AD7875 (0–5 V), the AD7876BQ's input structure is specifically optimized for ±10 V full-scale operation, with dedicated biasing to maintain linearity and offset stability across temperature.

Can the AD7876BQ be used with an external clock instead of the internal oscillator?

Yes, the AD7876BQ supports both internal and external clocking. To use the internal laser-trimmed oscillator, tie the CLK pin to VSS (−5 V). To use an external TTL-compatible clock, drive CLK with a 2.5 MHz signal (or other frequency per timing specs) while leaving CLK unconnected to VSS. External clocking allows synchronization with system clocks or precise jitter control. Conversion time becomes dependent on external clock period (e.g., 8 μs max at 2.5 MHz), and all timing parameters in Table 3 apply. The internal clock remains disabled when CLK is actively driven.

What are the key differences between AD7876BQ and AD7870BQ?

The AD7876BQ and AD7870BQ share the same SOIC-24 package, pinout, timing, and interface logic, but differ critically in analog input range and scaling: AD7876BQ accepts ±10 V inputs using a 2.1R/7R/3R network and outputs twos-complement codes (1 LSB = 4.88 mV), while AD7870BQ accepts ±3 V inputs with 15 kΩ input resistance and 1 LSB = 1.46 mV. AD7876BQ specifies ±6 LSB full-scale error over temperature; AD7870BQ specifies ±5 LSB. Dynamic specs like SNR are documented for AD7870/AD7875 only - AD7876BQ dc accuracy is fully characterized, but ac performance is typical and not production-tested.