TSX7191ILT datasheet(18/25 Pages) STMICROELECTRONICS

18 / 25 page

Application information

TSX7191, TSX7191A

18/25

DocID026747 Rev 3

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

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

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

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

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

stress duration.

4.7

High values of input differential voltage

In a closed loop configuration, which represents the typical use of an op amp, the input

differential voltage is low (close to Vio). However, some specific conditions can lead to

higher input differential values, such as:

operation in an output saturation state

operation at speeds higher than the device bandwidth, with output voltage dynamics

limited by slew rate.

use of the amplifier in a comparator configuration, hence in open loop

Use of the TSX7191, TSX7191A in comparator configuration, especially combined with

high temperature and long duration can create a permanent drift of Vio.

Months

1000 h

12 months

24 h

365.25 days

maxV

op with Vicm

∆V

iodr ift

month s

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