# FAQ

Welcome to the Texas Instruments Logic Forum FAQ page! This page contains answers to frequently asked questions we receive in the Logic Forum. Our list of FAQ topics can be found along the right side of this screen. If you have searched through our FAQs and cannot find the answer to a Logic-related question, please post your question in the Logic Forum.

## Most Common Logic Related Questions

#### Maximum Junction Temperature

What is the maximum junction temperature for <logic device>?

The vast majority of logic devices do not list a maximum junction temperature (TJ(max)) on the datasheet.

For logic devices, TJ(max) is equal to the maximum storage temperature (Tstg(max)) as listed in the Absolute Maximum Ratings table of the datasheet unless otherwise specified.

It is extremely unlikely for any logic device to ever reach its maximum junction temperature while being operated within the datasheet rated values.  I will keep this short, but suffice it to say that if you operate a logic device at its maximum datasheet ratings for ambient temperature and output power, the junction temperature will likely still be far below the maximum allowable value.  If you are interested in learning more about power dissipation in logic devices, please read our application report entitled CMOS Power Consumption and Cpd Calculation.

#### Effects of Slow or Floating Signals on CMOS Inputs

Can I leave a CMOS input floating?

What will happen if there is noise on a CMOS input?

What can I do to fix these issues?

Our datasheets list a maximum edge rate for input signals to CMOS devices which should not be violated, labelled as Δt/Δv in the Recommended Operating Conditions section of the datasheet.

To keep this answer short and to the point, slow or floating inputs on CMOS devices can cause excessive supply currents, oscillations, and damage to the device.  For a full explanation, please read our application report entitled Implications of Slow or Floating CMOS Inputs

#### Part Number has E4/G4 Suffix

Why does a device have an E4/G4 suffix?

What is the difference between SN74xxG4 and SN74xx?

In short, there will be no difference between a device labelled SN74xxG4 and SN74xx.

Historically, G4 and E4 suffixes meant that the devices were rated to be “Green” or “Lead Free.” However, as time has passed, all devices have been pushed to these new “Green” or “Lead Free” standards, but the specific part orderables have remained available so that customers have had a consistent orderable part number.

To check on the “Green” status of a part, you can put your part number into the search at the following link.
Material Content Search Tool

For definitions of E4, G4 suffixes, please refer to the following:
Environmental Information
Environmentally Friendly Solutions from TI

You can also refer to the end of the datasheet in the Part Orderable Addendum to see the “Eco Plan” of a specific part orderable, where the terminology is defined by the following document:
Green and Lead Free Definitions