TSU112IYST datasheet(20/32 Pages) STMICROELECTRONICS

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5.4

Long term input offset voltage drift

To evaluate product reliability, two types of stress acceleration are used:

•

Voltage acceleration, by changing the applied voltage

•

Temperature acceleration, by changing the die temperature (below the maximum junction temperature

allowed by the technology) with the ambient temperature.

The voltage acceleration has been defined based on JEDEC results, and is defined using Equation 2.

Equation 2

AFV

VS VU

–

(

)

Where:

AFV is the voltage acceleration factor

β is the voltage acceleration constant in 1/V, constant technology parameter (β = 1)

VS is the stress voltage used for the accelerated test

VU is the voltage used for the application

The temperature acceleration is driven by the Arrhenius model, and is defined in Equation 3.

Equation 3

AFT

------

–

Where:

AFT is the temperature acceleration factor

Ea is the activation energy of the technology based on the failure rate

k is the Boltzmann constant (8.6173 x 10-5 eV.K-1)

TU is the temperature of the die when VU is used (°K)

TS is the temperature of the die under temperature stress (°K)

The final acceleration factor, AF, is the multiplication of the voltage acceleration factor and the temperature

acceleration factor (Equation 4).

Equation 4

AFT AFV

AF is calculated using the temperature and voltage defined in the mission profile of the product. The AF value can

then be used in Equation 5 to calculate the number of months of use equivalent to 1000 hours of reliable stress

duration.

Equation 5

Months

AF 1000 h

12 months 24 h

365.25 days

(

)

To evaluate the op amp reliability, a follower stress condition is used where VCC is defined as a function of the

maximum operating voltage and the absolute maximum rating (as recommended by JEDEC rules).

The Vio drift (in µV) of the product after 1000 h of stress is tracked with parameters at different measurement

conditions (see Equation 6).

Equation 6

VCC

maxVop with Vicm

VCC 2

The long term drift parameter (ΔVio), estimating the reliability performance of the product, is obtained using the

ratio of the Vio (input offset voltage value) drift over the square root of the calculated number of months (Equation

7).

Equation 7

∆Vio

Viodrift

month s

(

)

TSU112IY

Long term input offset voltage drift

DS13616 - Rev 1

page 20/32

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