TSU101RILT datasheet(19/33 Pages) STMICROELECTRONICS

19 / 33 page

DocID024317 Rev 2

19/33

TSU101, TSU102, TSU104

Application information

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.

4.5

Schematic optimization aiming for nanopower

To benefit from the full performance of the TSU10 series, the impedances must be

maximized so that current consumption is not lost where it is not required.

For example, an aluminum electrolytic capacitance can have significantly high leakage. This

leakage may be greater than the current consumption of the op-amp. For this reason,

ceramic type capacitors are preferred.

For the same reason, big resistor values should be used in the feedback loop. However,

there are three main limitations to be considered when choosing a resistor.

When the TSU10x series is used with a sensor: the resistance connected between the

sensor and the input must remain much higher than the impedance of the sensor itself.

Noise generated: a100 kΩ resistor generates 40

, a bigger resistor value generates

even more noise.

Leakage on the PCB: leakage can be generated by moisture. This can be improved by

using a specific coating process on the PCB.

Months

AF 1000 h

12 months

24 h

365.25 days

()

⁄

VCC

maxVop with Vicm

VCC 2

⁄

ΔVio

Viodrift

months

()

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