AD688BQ

Overview

The AD688BQ is a high precision ±10 V tracking voltage reference manufactured by Analog Devices Inc. It utilizes a proprietary ion-implanted buried Zener diode and laser-trimmed thin-film resistors to achieve low initial error of ±2 mV and low temperature drift of ±3 ppm/°C over the −40°C to +85°C range. The device features full Kelvin connections for force and sense terminals, ensuring accurate load regulation. It includes three internal amplifiers (A1-A4) configured to provide buffered outputs with a maximum output current of ±10 mA per amplifier. The unit operates on dual supplies (+VS and -VS) and offers flexible output configurations.

Feature Summary

• Precision tracking outputs with integrated Kelvin force and sense connections to eliminate wire resistance errors.
• Low initial error and low temperature drift achieved through ion-implanted buried Zener technology and laser trimming.
• Internal buffer amplifiers A3 and A4 provide high impedance ground sense and boost drive capability for long lines or high current loads.
• Calibration capabilities via Gain Adj and Balance Adj pins allow fine-tuning of output magnitude and symmetry without altering operating conditions.

Applications

• Precision measurement systems requiring 12-bit absolute accuracy without periodic recalibration.
• System calibration references providing known voltages for software-based calibration.
• Bipolar Wheatstone bridge driver circuits for transducer excitation.
• Driving analog-to-digital and digital-to-analog converters with transient load requirements.

Procurement Notes

Verify the specific grade B designation ensures the ±2 mV initial error specification. Confirm the Q-16 ceramic DIP package option matches the target PCB footprint. Check for lead-free compliance if RoHS standards are required, noting that standard BQ parts may differ from ARWZ variants. Ensure supply voltages align with the specified operational range for optimal line and load regulation performance.

Selection Notes

Select the AD688BQ when strict symmetry between positive and negative rails is critical, as indicated by the low tracking error specification. Consider the CERDIP package for applications requiring robust mechanical stability or hermetic sealing compared to plastic SOIC options. Evaluate the need for external noise reduction capacitors if low-frequency noise performance below 6 µV p-p is insufficient for the application.

Part Context

The AD688 series represents a family of monolithic precision voltage references designed to replace discrete trimming potentiometers. The B grade specifically targets applications demanding tighter initial accuracy than the A grade while maintaining the same thermal performance characteristics. It serves as a complete reference solution including buffer amplifiers, reducing component count in high-performance data acquisition designs.

Replacement Considerations

The AD688AQ is a compatible alternative within the same family offering slightly different initial error specifications but identical tracking and drift performance. Both share the same pinout and functional architecture, allowing for direct substitution in existing designs without circuit modification.