SN74AHC1G09: For Vo=Vcc+0.7 defintion

The V_O/I_OK entries in 6.1 and 6.3 contradict each other. In theory, an open-collector output should be over-voltage tolerant in the high-impedance state; this is implemented by omitting the ESD protection diode to V_CC. If this is the case, the V_O entry in 6.1 is a copy-paste error; but if there is an ESD diode, the entry in 6.3 is wrong.

The AHC1G09 devices from other manufacturers (Nexperia, ONSemi, Toshiba) have over-voltage tolerant outputs, so I'd guess that it is the 6.1 entry that is wrong. (Curiously, the Diodes 74AHC1G09 datasheet has the same error as TI's datasheet …)

The circuit that converts from 5 V to 3.3 V is guaranteed to work.
The circuit that converts from 3.3 V to 5 V works if the output is over-voltage tolerant.

Hi Clemens,

Thank you for your explanation. In datasheet of SN74AHC1G09, it has sentences like below. Does it mean that the output is over-voltage tolerant, so it's possible to up-translate from 3.3V to 5V?

Best Regards,

Sam Lee

Hello Sam,

I think that the datasheet may be in error, but I will have to look into our design documents or order devices to verify this and correspondingly update/correct the datasheet to be more clear on this one way or the other. 

Please allow some time to verify.

Best,
Michael

Hi Michael,

My customer is waiting for your confirmation. Can you update if the up-translation is possible?

Best Regards,
Sam Lee

Hello Sam,

I apologize for the delay, but we are looking into it.

I should have a response to you by tomorrow.

Best,

Michael

Hello Sam,

We were not able to verify, so I will have to order parts and test them on the bench in order to complete this request.

I should have mentioned this earlier. If you have parts available, there should be a quick way to check with those parts.
If you use the diode checker on a handheld DMM and check for a diode from the output to VCC, then that would tell you whether or not it will clamp the output higher than VCC. If there is no diode present from OUT to VCC, then you are fine to have a higher output voltage on the device relative to VCC.

Best,
Michael

Hi Michael,

Thank you for your support.

In a test, they checked that the up-translation from 3.3V to 5V is possible. In that case, does it have no issue on stress or reliability perspectives? If no issue, they'll use this way.


Best Regards,
Sam Lee

The question was only whether there is an ESD protection diode from the output to VCC.

Your test has shown that there is not, which implies that the output is designed for up-translation, and is guaranteed to be 5 V tolerant, permenently.