SN74AVCH16T245: 1D1IR and 2DIR reference to VCCB compared to VCCA.

Kannan Sockalingam

Part Number: SN74AVCH16T245

Hi there, customer is using SN74AVCH16T245ZQLR in an older design (the device might be obsolete now), but there are parts in the field. In the datasheet, it says to reference 1DIR and 2DIR pins to VCCA, but on the board, it was mistakenly connected to VCCB. What is the impact of this?

Note:

VCCA = 1.8V

VCCB = 3.3V

Thanks in advance.

over 4 years ago

+1 Karan Kotadia over 4 years ago

TI__Genius 16735 points

Hi Kannan,

Luckily since VccB > VccA, and the device has over-voltage tolerant inputs this condition will not damage your part and you may be able to get it work fine.

You have to just make you understand that internally, Dir is still referenced to VccA. So to drive Dir LOW, a VIL of <1.17V has to be met.

Regards,

Karan

0 Kannan Sockalingam over 4 years ago in reply to Karan Kotadia

TI__Intellectual 1885 points

Thank you. Do you expect any increase in total power consumption due to this mis-connection?

+1 Karan Kotadia over 4 years ago in reply to Kannan Sockalingam

TI__Genius 16735 points

Hi Kannan,

Your supply consumption should not change but you will see a higher input leakage into the DIR pins due to the higher voltage applied. It will not be significant, the max Il spec'd is 1uA and so I suspect the max Ilov or over-voltage input leakage will be around 1.5uA.

Regards,

Karan

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SN74AVCH16T245: 1D1IR and 2DIR reference to VCCB compared to VCCA.