Analog Devices Inc. AD780BN

Overview

AD780BN from Analog Devices is an ultrahigh-precision, pin-programmable 2.5 V/3.0 V band gap voltage reference in 8-lead PDIP package, featuring 3 ppm/°C max drift over −40°C to +85°C, ±1 mV max initial accuracy, and 100 nV/√Hz wideband noise. It operates from 4.0 V to 36 V input and supports series/shunt mode for ±2.5 V or ±3.0 V outputs - widely used as reference for 16-bit+ ADCs like AD7884 and Σ-Δ converters including AD7710.

For engineers reviewing the AD780BN datasheet, AD780BN pinout, AD780BN application, or AD780BN equivalent, key selection criteria include its low-drift performance across industrial temperature range, dual-mode output configuration, temperature-sensing capability via dedicated TEMP pin, and compatibility with high-resolution data converter reference requirements without external buffering.

Technical Context

The AD780BN implements a laser-trimmed band gap core with two NPN transistors (Q6/Q7) differing 12× in emitter area to generate a PTAT current, combined with V_BE to produce a stable V_BG. Its low-headroom amplifier enables 3.0 V output from as low as 4.5 V supply - a 20% dynamic range boost over legacy 2.5 V references in 5 V ADC systems.

It delivers stable operation under all load conditions with only a 1 µF bypass capacitor, supports sourcing/sinking up to 10 mA, and integrates a linear temperature output (560 mV @ 25°C, 1.9 mV/°C) usable as a calibrated transducer while maintaining reference stability - no region of instability exists unlike competing references.

Key Specifications

Pinout & Package

AD780BN is housed in an 8-lead plastic dual in-line package (PDIP, N-8), with thermal resistance θ_JA = 49.8°C/W and θ_JC = 37.4°C/W under JEDEC standard PCB conditions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar precision voltage reference applications.

Compared with LT1019A-2.5 and AD680, the AD780BN offers superior drift performance (3 ppm/°C vs. 10/10), dual-output configurability, integrated temperature sensing, and broader operating voltage range - making it the preferred choice for metrology, calibration, and high-end data acquisition where reference fidelity is non-negotiable.

Availability

AD780BN is available at Aetrix Electronics and suitable for high-resolution data acquisition, precision instrumentation calibration, and medical diagnostic signal chain applications requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for AD780BN 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, serving industrial, communications, automotive, and healthcare markets since 1965.

The AD780 product line was designed specifically for ultraprecise voltage reference applications in high-resolution data converters and metrology-grade instrumentation - emphasizing low drift, low noise, and operational flexibility across diverse system architectures.

FAQ

What output voltage options does the AD780BN support, and how is selection implemented?

The AD780BN supports pin-programmable 2.5 V or 3.0 V output. Selection is made by grounding Pin 8 (SEL) for 3.0 V operation or leaving it unconnected for 2.5 V output. This hardware-based configuration requires no external logic or firmware control, ensuring deterministic behavior across power cycles and temperature extremes. The AD780BN maintains ±1 mV accuracy and 3 ppm/°C drift in both modes, verified over −40°C to +85°C.

How does the AD780BN achieve stability with large capacitive loads, and what is the minimum recommended bypass capacitor?

The AD780BN is internally compensated to remain stable under all load conditions when a 1 µF ceramic or tantalum capacitor is placed between Pin 1 (VIN) and ground. This bypass capacitor suppresses supply noise and ensures loop stability even when driving >1 nF of load capacitance - common in ADC reference inputs and long PCB traces. Unlike many references, the AD780BN exhibits no region of instability, eliminating need for external isolation resistors or complex compensation networks.

Can the AD780BN generate negative reference voltages, and what configuration is required?

Yes, the AD780BN supports negative reference generation in shunt mode: connect VIN and OUT to ground, then tie the GND pin to a negative supply via a bias resistor (e.g., Figure 24). In series mode with bootstrapping (Figure 25), it delivers up to 100 mA of −2.5 V output. Both configurations require no external op amps or precision resistors - leveraging the AD780BN's ability to sink current and maintain regulation without added components.

What is the function and accuracy of the TEMP pin on the AD780BN, and how should it be interfaced?

The TEMP pin (Pin 3) provides a factory-calibrated linear voltage output of 560 mV ±60 mV at 25°C with 1.9 mV/°C sensitivity. To avoid injecting error into VOUT, it must be buffered using a low-input-bias-current op amp (e.g., OP07, AD820, or AD711), limiting current draw to <1 µA. Unbuffered loading causes ∆VOUT = 5.8 mV/µA (2.5 V mode) or 6.9 mV/µA (3.0 V mode), degrading reference accuracy.

Is the AD780BN compatible with existing AD680 or LT1019A-2.5 designs, and what modifications are needed?

The AD780BN is a pin-compatible performance upgrade for the LT1019A-2.5 and AD680 in PDIP packages, sharing identical pinout and footprint. No PCB changes are required. However, Pin 7 (DNC) differs functionally from LT1019's self-heater pin and must remain unconnected. For AD680 designs, Pin 8 (SEL) must be grounded or left open to configure output voltage - a minor schematic update that unlocks 3.0 V operation and 3× lower drift without layout revision.