8.3.3 Thermal Hysteresis

Thermal hysteresis for the REF50xx 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. Thermal hysteresis can

be expressed as Equation 4:

PRE

POST

6

HYST

NOM

V

V

V

10 (ppm)

V

æ

ö

-

=

×

ç

÷

ç

÷

è

ø

(4)

where

• VHYST = thermal hysteresis (in units of ppm)

• VNOM = the specified output voltage

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

• VPOST = output voltage measured after the device has been cycled from 25°C through the specified

temperature range of –40°C to 125°C and returned to 25°C

8.3.4 Noise Performance

Typical 0.1Hz to 10Hz voltage noise for each member of the REF50xx family is specified in the Electrical

Characteristics table. The noise voltage increases with output voltage and operating temperature. Additional

filtering can be used to improve output noise levels, although take care to make sure the output impedance does

not degrade performance.

For additional information about how to minimize noise and maximize 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

V

OUT

V

IN

GND

DNC

NC

TRIM/NR

REF50xx

C1

1 F

m

+V

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. These changes and the associated package stress

on the die cause the output voltage in precision voltage references to deviate over time. 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.

OUT

OUT

6

t 0

t n

t n

OUT t 0

(V

V

)

LTD(ppm)

10

V

u

(5)

where

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

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

REF5010, REF5020, REF5025, REF5030, REF5040, REF5045, REF5050

SBOS410L – JUNE 2007 – REVISED OCTOBER 2024

www.ti.com

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