REF50 datasheet(25/52 Pages) TI2

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8.3.3 Thermal Hysteresis

Thermal hysteresis for the REF50xx is 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. Equation 4 shows thermal hysteresis.

VHYST= VPRE−VPOST

VNOM ×106ppm

(4)

where

• VHYST = thermal hysteresis (ppm)

• VNOM = the specified output voltage

• VPRE = output voltage measured at 25°C pre-temperature cycling

• VPOST = output voltage measurement after the device cycles from 25°C through the specified temperature

range of –40°C to 125°C and returns to 25°C

8.3.4 Noise Performance

Typical 0.1Hz to 10Hz voltage noise for each member of the REF50xx family is specified Section 6.5 and

Section 6.6. The noise voltage increases with output voltage and operating temperature. Use additional filtering

to improve output noise levels. If using additional filtering, verify that the output impedance does not degrade

performance.

For additional information about minimizing noise and maximizing performance in mixed-signal applications,

such as data converters, refer to the How a Voltage Reference Affects ADC Performance Part 1, How a Voltage

Reference Affects ADC Performance Part 2, and How a Voltage Reference Affects ADC Performance Part 3

analog design journals.

DNC

TEMP

OUT

GND

DNC

TRIM/NR

REF50xx

1 F

SUPPLY

Figure 8-4. Noise Reduction Using the TRIM/NR Pin

8.3.5 Long-Term Stability

Due to aging and environmental effects, all semiconductor devices experience physical changes of the

semiconductor die and the packaging material over time. Over time, the changes and the associated package

stress on the die cause the output voltage in precision voltage references to deviate. The value of such change

is specified in the data sheet by a parameter called the long-term stability (also known as the long-term drift

(LTD)). Equation 5 shows how LTD is calculated. Note that the LTD value is positive if the output voltage drifts

higher over time and negative if the voltage drifts lower over time. Figure 6-23 through Figure 6-30 show the drift

of the output voltage for REF50xx over the first 4000 operating hours.

LTDppm t=n= VOUTt=0−VOUTt=n

VOUTt=0 ×106

(5)

where

• LTD(ppm)|t=n = long-term stability (ppm)

• VOUT|t=0 = output voltage at time = 0 hr

• VOUT|t=n = output voltage at time = n hr

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REF50, REF50E

SBOS410O – JUNE 2007 – REVISED OCTOBER 2025

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