8 Parameter Measurement Information

8.1 Long-Term Stability

Buried zener references typically exhibit very stable long term stability and are used as an ultra stable reference

for internal calibration of the system. The long-term stability value is tested in a typical setup that reflects

standard PCB board manufacturing practices for references with a strain modulation structure around the device.

The boards are made of standard FR4 material with 35µm of Copper. The devices have been soldered through

standard reflow.

Long term stability setup is designed with utmost care to minimize impact of thermocouple error, strain impact

and mechanical vibration in long term stability measurement. The boards are maintained at 25°C in an air drift

oven with heater temperature set to 115°C in powered on condition for long term stability measurement.

Typical long-term stability characteristic is expressed as a deviation over time. Figure 8-1 shows the typical drift

value for the VREF_Z is 3ppm from 0 to 1000 hours. Drift of REF80 gets flat after 1000 hours. Powered-up burn-in

at room temperature helps REF80 to achieve best long term stability performance.

Power cycle has minimal impact on the stability of the VREF_Z and doesn't change the settled profile. Figure 8-2

shows the behavior of the output when the devices are powered off for 24 hours.

Figure 8-1. Long Term Stability (VREF_Z)

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REF80

SNAS856A – SEPTEMBER 2024 – REVISED MARCH 2025

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