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REF2912, REF2920, REF2925

REF2930, REF2933, REF2940

SBVS033C – JUNE 2002 – REVISED JUNE 2016

www.ti.com

Product Folder Links: REF2912 REF2920 REF2925 REF2930 REF2933 REF2940

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Copyright © 2002–2016, Texas Instruments Incorporated

Feature Description (continued)

Supply voltages below the specified levels can cause the REF29xx to momentarily draw currents greater than

the typical quiescent current. Using a power supply with a fast rising edge and low output impedance easily

prevents this.

8.3.2 Thermal Hysteresis

Thermal hysteresis for the REF29xx is defined as the change in output voltage after operating the device at

25°C, cycling the device through the specified temperature range, and returning to 25°C, and can be expressed

as shown in Equation 1.

where

•

VHYST = calculated hysteresis

•

VPRE = output voltage measured at 25°C pretemperature cycling

•

VPOST = output voltage measured when device has been operated at 25°C, cycled through specified range

–40°C to 125°C and returned to operation at 25°C

(1)

8.3.3 Temperature Drift

The REF29xx is designed to exhibit minimal drift error, defined as the change in output voltage over varying

temperature. Using the box method of drift measurement, the REF29xx features a typical drift coefficient of 20

ppm from 0°C to 70°C— the primary temperature range of use for many applications. For industrial temperature

ranges of –40°C to 125°C, the REF29xx family drift increases to a typical value of 50 ppm.

8.3.4 Noise Performance

The REF29xx generates noise less than 50 µVPP between frequencies of 0.1 Hz to 10 Hz, and can be seen in

Figure 20. The noise voltage of the REF29xx increases with output voltage and operating temperature. Additional

filtering may be used to improve output noise levels, however, take care ensuring the output impedance does not

degrade AC performance.

8.3.5 Long-Term Stability

Long-term stability refers to the change of the output voltage of a reference over a period of months or years.

This effect lessens as time progresses as is apparent by the long-term stability curves. The typical drift value for

the REF29xx is 24 ppm from 0 to 1000 hours, and 15 ppm from 1000 to 2000 hours. This parameter is

characterized by measuring 30 units at regular intervals for a period of 2000 hours.

8.3.6 Load Regulation

Load regulation is defined as the change in output voltage due to changes in load current. Load regulation for the

REF29xx is measured using force and sense contacts as pictured in Figure 26. The force and sense lines tied to

the contact area of the output pin reduce the impact of contact and trace resistance, resulting in accurate

measurement of the load regulation contributed solely by the REF29xx. For applications requiring improved load

regulation, force and sense lines must be used.