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

then be used in Eq. (5) to calculate the number of months of use equivalent to 1000 hours of reliable stress

duration.

Montℎs=AF×1000ℎ×12montℎs/24ℎ×365.25days

(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

Eq. (6)).

VCC=maxVop witℎVicm=Vcc2

(6)

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 (Eq. (7)).

∆Vio= Viodrift

montℎs

(7)

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 Eq. (8).

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

(8)

Where:

ΔVio is the long term drift parameter in µV.√month

top is the operating time seen by the device, in months

Top is the operating temperature

VCC is the power supply during operating time

VCC nom is the nominal VCC at which the ΔVio is computed (5 V for TSV78x)

Ea is the activation energy of the technology (here 0.7 eV).

5.4

Unused channel

When one of the two channels of the TSV78x is not used, it must be properly connected in order to avoid internal

oscillations that can negatively impact the signal integrity on the other channel, as well as the current

consumption. Two different configurations can be used:

Gain configuration: the channel can be set in gain, the input can be set to any voltage within the Vicm operating

range.

Comparator configuration: the channel can be set to a comparator configuration (without negative feedback). In

this case, positive and negative inputs can be set to any value provided these values are significantly different

(100 mV or more, to avoid oscillation between positive and negative state) and the differential input is lower than

the maximum specified in the operating range (maximum 2 V), or the input current is limited to less than 10 mA to

avoid damaging the circuit.

5.5

EMI rejection

The electromagnetic interference (EMI) rejection ratio, or EMIRR, describes the EMI immunity of operational

amplifiers. An adverse effect that is common to many op amps is a change in the offset voltage as a result of RF

signal rectification. EMIRR is defined in Eq. (9):

EMIRR=20.log Vin pp∆Vio

(9)

The TSV78x has been specially designed to minimize susceptibility to EMIRR and shows a low sensitivity. As

visible in Figure 42, EMI rejection ratio has been measured on both inputs and output, from 400 MHz to 2.4 GHz.

TSV781, TSV782

Application information

DS14011 - Rev 7

page 19/34