TSB711 datasheet(19/36 Pages) STMICROELECTRONICS

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5.5

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:

(2)

AFV = еβ.(VS - VU)

Where:

AFV is the voltage acceleration factor

β is the voltage acceleration coefficient 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 as follows:

(3)

AFT=eEak. 1TU−1TS .

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.

(4)

AF = 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.

(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 ratings (as recommended by JEDEC rules). Vio drift (in

µV) of the product after 1000 h of stress is tracked with parameters at different measurement conditions.

(6)

VCC = max(VOP) with Vicm = VCC/2

The long term drift parameter ΔVio (in µV.month-1/2), 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.

(7)

∆Vio=Viodrift

montℎs

Where Vio drift is the measured drift value in the specified test conditions after 1000 h stress duration.

The Vio final drift, in µV, to be measured on the device in real operation conditions can be computed from:

(8)

Vio final drifttop,Top,VCC =∆Vio, 25°C. top.eβ.VCC−VCC nom.eEak. 1297− 1Top

TSB711, TSB711A, TSB712, TSB712A, TSB714, TSB714A

Long term input offset voltage drift

DS12487 - Rev 6

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