8.2 Long-Term Stability

One of the key parameters of the REF70 references is long-term stability. Typical characteristic expressed as:

understand that long-term stability is not ensured by design and that the output from the device may shift beyond

the typical 18 ppm specification at any time. For systems that require highly stable output voltages over long

periods of time, the designer should consider burning in the devices prior to use to minimize the amount of

output drift exhibited by the reference over time.

Time (Hr)

0

50

100

150

200

250

-40

-30

-20

-10

0

10

8.3 Thermal Hysteresis

Thermal hysteresis is measured with the REF70 soldered to a PCB, similar to a real-world application. Thermal

hysteresis for the device 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. The PCB was baked at 150°C for 30

minutes before thermal hysteresis was measured. Hysteresis can be expressed by Equation 1:

6

PRE

POST

HYST

NOM

| V

V

|

V

10

ppm

V

§

·

u

¨

¸

©

¹

(1)

where

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

8.4 Power Dissipation

The REF70 voltage references are capable of source and sink up to 10 mA of load current across the rated input

voltage range. However, when used in applications subject to high ambient temperatures, the input voltage and

load current must be carefully monitored to ensure that the device does not exceeded its maximum power

dissipation rating. The maximum power dissipation of the device can be calculated with Equation 2:

J

A

D

JA

T

T

P

R

T

u

(2)

where

REF70

SNAS781 – OCTOBER 2020

www.ti.com

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