SN74LVC1T45: missing supply at one pin

kushal banerjee

Part Number: SN74LVC1T45

Hi,
We are using SN74LVC1T45 as level translator.
Currently, its VCCa is supplied but no VCCb is supplied.
We are receiving 2.51V at the VCCb supply pin (6th pin).
Please clarify, why this residual voltage is coming ?

over 7 years ago

0 Dylan Hubbard over 7 years ago

TI__Mastermind 45725 points

Hi Kushal,

I'm going to need a little more info to answer this like a schematic and maybe a short summary of the application. We can start with that and move on from there to get this issue debugged.

0 kushal banerjee over 7 years ago in reply to Dylan Hubbard

Prodigy 210 points

Hi Dylan,

I have attached the schematics of the IC being used.
It is being used to convert Received signals to 3.3V from 5V level.
Unfortunately, the VCCB source(i.e 5V - 6th pin) is not present but 3.3V is coming fine.
In this case, we are getting 2.51V at the 6th pin.
Our doubt is, whether 6th pin is driven by 3.3V ?

0 Dylan Hubbard over 7 years ago in reply to kushal banerjee

TI__Mastermind 45725 points

Hi Kushal,

So it seems that you are intending the voltage at the VCCB pin to be 5 V , but is half that. I don't see anything wrong with how you have connected this device. Is this maybe an issue with the origin of the 5 V supply?

0 kushal banerjee over 7 years ago in reply to Dylan Hubbard

Prodigy 210 points

Hi Dylan,

I will put in other way.
Consider that VCCA is having the 3.3V supply, but VCCB is not connected to the 5V supply.
Still, there is voltage coming at 6th pin (i.e, VCCB).

0 Dylan Hubbard over 7 years ago in reply to kushal banerjee

TI__Mastermind 45725 points

Hi Kushal,

I see what you are saying now. So pin 6 isn't connected to anything? When you disconnect the VCCA pin do you still see this voltage on VCCB when the rest of the system is still operating?

0 Dylan Hubbard over 7 years ago in reply to Dylan Hubbard

TI__Mastermind 45725 points

Hi Kushal,

Is this something you still assistance on? I haven't heard from you in awhile. I'm going to mark it is resolved for now until I hear back from you. Thanks!

0 kushal banerjee over 7 years ago in reply to Dylan Hubbard

Prodigy 210 points

Yes, when we removed this IC, the voltage was also removed. It was because of this IC only. You can close this thread.

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SN74LVC1T45: missing supply at one pin