We often get similar questions posted about TI voltage level translation products. This list will grow as we receive more questions that have common answers.
What is the difference between TI's TXB, TXS, LSF, LV1T, and other types of translation families?
-See section 3 of the following application report for more information on the different types of translation families: http://www.ti.com/lit/pdf/scea030
When can a translator be used in an open drain vs push pull system?
- In general, unless signaling standards prevent the usage, either translator can be in either other type of system because the receiving input usually cannot distinguish between the two. The only real concern to watch out for is bus contention, which is when one device tries to drive a line low while another tries to drive high. In that case, an open-drain system might be more beneficial.
How do I design with the LSF devices?
-See the following application report for desining with the LSF family: http://www.ti.com.cn/cn/lit/an/slva675b/slva675b.pdf
How do I know when translators are bidirectional?
-There are two ways:
1. A translator will specifically mention "bidirectional" or "auto direction sensing" in the datasheet
2. The translator will have a DIR pin, which allows the user to manually control the translation direction.
How does auto direction sensing for the TXS and TXB parts work?
-See the following application reports: TXS (http://www.ti.com/lit/an/scea044/scea044.pdf), TXB (http://www.ti.com/cn/lit/pdf/SCEA043)
Maximum Junction Temperature
What is the maximum junction temperature for <logic device>?
ANSWER
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?
ANSWER
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?
ANSWER
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
General Part Naming Conventions
Can you help me understand the part numbers?
There are so many part numbers, is there a logic part number naming convention?
ANSWER
Please see the graphic below for a good overview for device names and package designators.
Please also note, while the information below is correct for the majority of parts, there are always exceptions to the rule.
Can I have VIN=5V when VCC = 0 V?
A common question we receive is "Can I have an input voltage when the supply voltage is turned off?"
Most of the time, the answer is yes. Many datasheets will specify "5-V Tolerant inputs" or over-voltage tolerant or some variation of that statement. In addition, another way to tell if a part has input voltage tolerance is to look at the Absolute Maximum Ratings. If the VI absolute maximum is a specific number, like 7 V, then the input can exist independent of Vcc. However, if Vcc is needed before any inputs occur, The absolute maximum voltage will look something like "Vcc + 0.5 V" indicating the forward-bias voltage of a diode going to Vcc prevents inputs higher than Vcc being safe.
EXCEPTION : In case,there is Ioff specification in the datasheet ,which basically mentions the conditions where Vcc=0V /0.2V and the test conditions have input /output at 5.5V or gnd . Ioff indicates that there is protection circuitry built into the design allowing user to have inputs while Vcc is turned off or 0V . The statement of "5-V tolerant inputs" usually accompany this datasheet. With Ioff specification , even though the abs max conditions indicate forward biasing diode to Vcc , you can apply any voltage at the inputs with Vcc powered down .
